# Test the high-level metadata tree in the core of littlefs
after = ['test_rbyd', 'test_btree']

# maximize lookahead buffer, we don't actually gc so we only get one pass
# of the disk for these tests
defines.LOOKAHEAD_SIZE = 'BLOCK_COUNT / 8'

# some helper functions
in = 'lfs.c'
code = '''
    static lfs_ssize_t lfsr_mdir_get(lfs_t *lfs, const lfsr_mdir_t *mdir,
            lfs_ssize_t rid, lfsr_tag_t tag, void *buffer, lfs_size_t size) {
        lfsr_data_t data;
        int err = lfsr_mdir_lookup(lfs, mdir, rid, tag, NULL, &data);
        if (err) {
            return err;
        }

        return lfsr_data_read(lfs, &data, buffer, size);
    }
'''

# test a single mroot
[cases.test_mtree_mroot]
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfsr_unmount(&lfs) => 0;
'''

# test a single mroot with attributes
[cases.test_mtree_mroot_attrs]
defines.N = [1, 3]
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);

    for (lfs_size_t i = 0; i < N; i++) {
        lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
                LFSR_ATTR(-1, UATTR(i), 0, BUF(&alphas[i % 26], 1)))) => 0;
    }

    for (lfs_size_t i = 0; i < N; i++) {
        uint8_t buffer[1];
        lfsr_mdir_get(&lfs, &lfs.mroot,
                -1, LFSR_TAG_UATTR(i), buffer, 1) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
    }

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    for (lfs_size_t i = 0; i < N; i++) {
        uint8_t buffer[1];
        lfsr_mdir_get(&lfs, &lfs.mroot,
                -1, LFSR_TAG_UATTR(i), buffer, 1) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
    }

    lfsr_unmount(&lfs) => 0;
'''

# test a single mroot with forced compaction
[cases.test_mtree_mroot_compact]
defines.N = [1, 3]
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);

    for (lfs_size_t i = 0; i < N; i++) {
        // force mroot to compact
        lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;

        lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
                LFSR_ATTR(-1, UATTR(i), 0, BUF(&alphas[i % 26], 1)))) => 0;
    }

    for (lfs_size_t i = 0; i < N; i++) {
        uint8_t buffer[1];
        lfsr_mdir_get(&lfs, &lfs.mroot,
                -1, LFSR_TAG_UATTR(i), buffer, 1) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
    }

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    for (lfs_size_t i = 0; i < N; i++) {
        uint8_t buffer[1];
        lfsr_mdir_get(&lfs, &lfs.mroot,
                -1, LFSR_TAG_UATTR(i), buffer, 1) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
    }

    lfsr_unmount(&lfs) => 0;
'''

# test a single mroot with many commits
[cases.test_mtree_mroot_many_commits]
defines.N = [5, 5000]
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);

    for (lfs_size_t i = 0; i < N; i++) {
        lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
                LFSR_ATTR(-1, UATTR(1), 0, BUF(&alphas[i % 26], 1)))) => 0;

        uint8_t buffer[4];
        lfsr_mdir_get(&lfs, &lfs.mroot,
                -1, LFSR_TAG_UATTR(1), buffer, 4) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
    }

    uint8_t buffer[4];
    lfsr_mdir_get(&lfs, &lfs.mroot,
            -1, LFSR_TAG_UATTR(1), buffer, 4) => 1;
    assert(memcmp(buffer, &alphas[(N-1) % 26], 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    lfsr_mdir_get(&lfs, &lfs.mroot,
            -1, LFSR_TAG_UATTR(1), buffer, 4) => 1;
    assert(memcmp(buffer, &alphas[(N-1) % 26], 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''


## Splitting operations ##

# specific split corner cases
[cases.test_mtree_uninline]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // prepare mroot with a large attr so the next entry can not fit
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // create a large entry that needs to be uninlined (but not split!)
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_uninline_split]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create 2 large entries that needs to be uninlined and split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our entries are still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_split]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // now add another large entry to the mdir, forcing a split
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;

    // assert mdir was split correctly
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;

    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was split correctly
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''


# try creating a range of entries that may or may not split our mtree
[cases.test_mtree_split_many]
defines.N = [5, 10, 20, 40, 80, 160, 320]
defines.FORCE_COMPACTION = [false, true]
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create entries
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(lfs_smax32(lfsr_mtree_weight(&lfs)-1, 0), -1),
            &mdir) => 0;

    mdir.mid.rid = 0;
    for (lfs_size_t i = 0; i < N; i++) {
        // force a compaction?
        if (FORCE_COMPACTION) {
            mdir.u.r.rbyd.eoff = -1;
            lfs.mroot.u.r.rbyd.eoff = -1;
        }

        lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                LFSR_ATTR(mdir.mid.rid, REG, +1,
                    BUF(&alphas[i % 26], 1)))) => 0;

        uint8_t buffer[4];
        lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                buffer, 4) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

        mdir.mid.rid += 1;
    }

    // try looking up each entry
    lfs_size_t i = 0;
    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
            i += 1;
        }
    }
    assert(i == N);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // try looking up each entry
    i = 0;
    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
            i += 1;
        }
    }
    assert(i == N);

    lfsr_unmount(&lfs) => 0;
'''

# create random entries
[cases.test_mtree_split_fuzz]
defines.N = [5, 10, 20, 40, 80, 160]
defines.FORCE_COMPACTION = [false, true]
defines.SEED = 'range(100)'
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";

    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // at least keep track of the number of entries we expect
    lfs_size_t count = 0;

    uint32_t prng = SEED;
    for (lfs_size_t i = 0; i < N; i++) {
        // choose a pseudo-random mid
        lfs_ssize_t mid = (lfs_ssize_t)(
                TEST_PRNG(&prng) % lfs_max32(lfsr_mtree_weight(&lfs), 1));
        // fetch mdir
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        // choose a pseudo-random rid
        mdir.mid.rid = TEST_PRNG(&prng) % (mdir.u.m.weight+1);

        // force a compaction?
        if (FORCE_COMPACTION) {
            mdir.u.r.rbyd.eoff = -1;
            lfs.mroot.u.r.rbyd.eoff = -1;
        }

        // add to rbyd, potentially splitting the mdir
        lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                LFSR_ATTR(mdir.mid.rid, REG, +1,
                    BUF(&alphas[i % 26], 1)))) => 0;

        // make sure we can look up the new entry
        uint8_t buffer[4];
        lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                buffer, 4) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

        count += 1;
    }

    // try looking up each entry
    lfs_size_t count_ = 0;

    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;

            count_ += 1;
        }
    }

    // the mtree is a bit difficult to simulate, but we can at least test
    // we ended up with the right number of entries
    assert(count_ == count);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // try looking up each entry
    count_ = 0;

    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;

            count_ += 1;
        }
    }

    // the mtree is a bit difficult to simulate, but we can at least test
    // we ended up with the right number of entries
    assert(count_ == count);

    lfsr_unmount(&lfs) => 0;
'''


## Dropping operations ##

# specific drop corner cases
[cases.test_mtree_drop]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // remove the entry, forcing the mdir to be dropped
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_compact]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // remove the entry, forcing the mdir to be dropped
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    // force mdir to compact while we're removing
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;

    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_uninline]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;

    // remove the entry as we compact, forcing the mdir to be dropped
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_uninline_split_l]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an mdir that needs to be split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;

    // remove the left entry as we compact, forcing the left
    // mdir to be dropped
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that one entry is still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that one entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_uninline_split_r]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an mdir that needs to be split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;

    // remove the right entry as we compact, forcing the right mdir
    // to be dropped
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that one entry is still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that one entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_uninline_split_both]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an mdir that needs to be split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;

    // remove both entries as we compact, forcing both mdirs to be dropped
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL),
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_split_l]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // now add another large entry to the mdir, forcing a split
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;

    // remove the left entry as we compact, forcing the left
    // mdir to be dropped
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that one entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that one entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_split_r]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // now add another large entry to the mdir, forcing a split
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;

    // remove the right entry as we compact, forcing the right
    // mdir to be dropped
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that one entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that one entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_split_both]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // now add another large entry to the mdir, forcing a split
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;

    // remove both entries as we compact, forcing both mdirs to be dropped
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL),
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

# try creating an mtree and then dropping mdirs
[cases.test_mtree_drop_many]
defines.N = [5, 10, 20, 40, 80, 160, 320]
defines.REMAINING = [20, 5, 1, 0]
if = 'N > REMAINING'
defines.FORCE_COMPACTION = [false, true]
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create entries
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(lfs_smax32(lfsr_mtree_weight(&lfs)-1, 0), -1),
            &mdir) => 0;

    mdir.mid.rid = 0;
    for (lfs_size_t i = 0; i < N; i++) {
        lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                LFSR_ATTR(mdir.mid.rid, REG, +1,
                    BUF(&alphas[i % 26], 1)))) => 0;

        uint8_t buffer[4];
        lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                buffer, 4) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

        mdir.mid.rid += 1;
    }

    // remove entries
    for (lfs_size_t i = 0; i < N - REMAINING; i++) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;

        // drop should make sure we never have empty mdirs
        assert(lfsr_mtree_isinlined(&lfs) || mdir.u.m.weight > 0);

        // force a compaction?
        if (FORCE_COMPACTION) {
            mdir.u.r.rbyd.eoff = -1;
            lfs.mroot.u.r.rbyd.eoff = -1;
        }

        lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                LFSR_ATTR(0, RM, -1, NULL))) => 0;
    }

    // try looking up each entry
    lfs_size_t i = N - REMAINING;
    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
            i += 1;
        }
    }
    assert(i == N);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // try looking up each entry
    i = N - REMAINING;
    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
            i += 1;
        }
    }
    assert(i == N);

    lfsr_unmount(&lfs) => 0;
'''

# this one has some pretty nasty corner cases
[cases.test_mtree_repeated_drop]
defines.N = [5, 10, 20, 40]
defines.FORCE_COMPACTION = [false, true]
defines.CYCLES = 10
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    for (lfs_size_t cycle = 0; cycle < CYCLES; cycle++) {
        // create entries
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(lfs_smax32(lfsr_mtree_weight(&lfs)-1, 0), -1),
                &mdir) => 0;

        mdir.mid.rid = 0;
        for (lfs_size_t i = 0; i < N; i++) {
            lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                    LFSR_ATTR(mdir.mid.rid, REG, +1,
                        BUF(&alphas[i % 26], 1)))) => 0;

            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

            mdir.mid.rid += 1;
        }

        // try looking up each entry
        lfs_size_t i = 0;
        for (lfs_ssize_t mid = 0;
                mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
                mid += lfsr_mbidweight(&lfs)) {
            lfsr_mdir_t mdir;
            lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
            for (mdir.mid.rid = 0;
                    mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                    mdir.mid.rid++) {
                uint8_t buffer[4];
                lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                        buffer, 4) => 1;
                assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
                i += 1;
            }
        }
        assert(i == N);

        // remove entries
        for (lfs_size_t i = 0; i < N; i++) {
            lfsr_mdir_t mdir;
            lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;

            // drop should make sure we never have empty mdirs
            assert(lfsr_mtree_isinlined(&lfs) || mdir.u.m.weight > 0);

            // force a compaction?
            if (FORCE_COMPACTION) {
                mdir.u.r.rbyd.eoff = -1;
                lfs.mroot.u.r.rbyd.eoff = -1;
            }

            lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                    LFSR_ATTR(0, RM, -1, NULL))) => 0;
        }

        assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
        assert(lfs.mroot.u.m.weight == 0);
    }

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    assert(lfs.mroot.u.m.weight == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_fuzz]
defines.N = [5, 10, 20, 40, 80, 160]
defines.FORCE_COMPACTION = [false, true]
defines.SEED = 'range(100)'
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";

    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // at least keep track of the number of entries we expect
    lfs_size_t count = 0;

    uint32_t prng = SEED;
    for (lfs_size_t i = 0; i < N; i++) {
        // choose a pseudo-random mid
        lfs_ssize_t mid = (lfs_ssize_t)(
                TEST_PRNG(&prng) % lfs_max32(lfsr_mtree_weight(&lfs), 1));
        // fetch mdir
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        // choose a pseudo-random rid
        mdir.mid.rid = TEST_PRNG(&prng) % (mdir.u.m.weight+1);
        // choose to create or delete
        uint8_t op = (lfs_size_t)mdir.mid.rid == mdir.u.m.weight
                ? 0
                : TEST_PRNG(&prng) % 2;

        // force a compaction?
        if (FORCE_COMPACTION) {
            mdir.u.r.rbyd.eoff = -1;
            lfs.mroot.u.r.rbyd.eoff = -1;
        }

        // create
        if (op == 0) {
            // add to rbyd, potentially splitting the mdir
            lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                    LFSR_ATTR(mdir.mid.rid, REG, +1,
                        BUF(&alphas[i % 26], 1)))) => 0;

            // make sure we can look up the new entry
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

            count += 1;

        // delete
        } else {
            lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                    LFSR_ATTR(mdir.mid.rid, RM, -1, NULL))) => 0;

            count -= 1;
        }
    }

    // try looking up each entry
    lfs_size_t count_ = 0;

    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;

        // drop should make sure we never have empty mdirs
        assert(lfsr_mtree_isinlined(&lfs) || mdir.u.m.weight > 0);

        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;

            count_ += 1;
        }
    }

    // the mtree is a bit difficult to simulate, but we can at least test
    // we ended up with the right number of entries
    assert(count_ == count);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // try looking up each entry
    count_ = 0;

    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;

        // drop should make sure we never have empty mdirs
        assert(lfsr_mtree_isinlined(&lfs) || mdir.u.m.weight > 0);

        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;

            count_ += 1;
        }
    }

    // the mtree is a bit difficult to simulate, but we can at least test
    // we ended up with the right number of entries
    assert(count_ == count);

    lfsr_unmount(&lfs) => 0;
'''


## Relocation operations ##

# specific relocation corner cases
[cases.test_mtree_relocate]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // prepare mroot with a large attr so the next entry can not fit
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // create a large entry that needs to be uninlined (but not split!)
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mtree has one mdir
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // force mdir to compact twice, this should relocate
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_t old_mdir = mdir;

    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, REG, 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mtree has one mdir
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_relocate_sibling_l]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create 2 large entries that needs to be uninlined and split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // force mdir to compact twice, this should relocate
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_t old_mdir = mdir;

    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, REG, 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_relocate_sibling_r]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create 2 large entries that needs to be uninlined and split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // force mdir to compact twice, this should relocate
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_t old_mdir = mdir;

    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, REG, 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // prepare mroot with an attr
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact twice, this should extend the mroot
    lfsr_mdir_t old_mroot = lfs.mroot;

    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_extend_twice]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
# force our block to compact by setting prog_size=block_size, we don't have
# any way to indirectly force the intermediary mroots to compact otherwise
defines.PROG_SIZE = 'BLOCK_SIZE'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // prepare mroot with an attr
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact 2x2 times, this should extend the mroot twice
    lfsr_mdir_t old_mroot = lfs.mroot;

    for (int i = 0; i < 4; i++) {
        lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
        lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;
    }
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_relocate_mroot]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // prepare mroot with an attr
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact twice, this should extend the mroot
    lfsr_mdir_t old_mroot = lfs.mroot;

    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // force mroot to compact twice again, this should relocate the mroot
    old_mroot = lfs.mroot;

    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_relocate_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // prepare mroot with a large attr so the next entry can not fit
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // create a large entry that needs to be uninlined (but not split!)
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mtree has one mdir
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // setup mroot to need to compact, this should trigger a relocation when
    // we relocate the mdir below
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_t old_mroot = lfs.mroot;

    // force mdir to compact twice, this should relocate
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_t old_mdir = mdir;

    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, REG, 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated our mdir
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mtree has one mdir
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mdir
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_split_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // setup mroot to need to compact, this should trigger a relocation when
    // we relocate the mdir below
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_t old_mroot = lfs.mroot;

    // now add another large entry to the mdir, forcing a split
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;

    // assert mdir was split correctly
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was split correctly
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_drop_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // setup mroot to need to compact, this should trigger a relocation when
    // we relocate the mdir below
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_t old_mroot = lfs.mroot;

    // remove the entry, forcing the mdir to be dropped
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was dropped
    assert(lfsr_mtree_weight(&lfs) == 0*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_uninline_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // force mroot to compact once, so the second compact below will trigger
    // a relocation
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // prepare mroot with a large attr so the next entry can not fit
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // create a large entry that needs to be uninlined (but not split!)
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact, this should trigger a relocation
    lfsr_mdir_t old_mroot = lfs.mroot;
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_uninline_split_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // force mroot to compact once, so the second compact below will trigger
    // a relocation
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // create 2 large entries that needs to be uninlined and split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact, this should trigger a relocation
    lfsr_mdir_t old_mroot = lfs.mroot;
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our entries are still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert we relocated our mroot
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

# this fuzz covers a lot of configuratinos
[cases.test_mtree_relocating_fuzz]
defines.N = [5, 10, 20, 40]
defines.FORCE_COMPACTION = [false, true]
defines.BLOCK_CYCLES = [5, 2, 1]
defines.SEED = 'range(500)'
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";

    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // at least keep track of the number of entries we expect
    lfs_size_t count = 0;

    uint32_t prng = SEED;
    for (lfs_size_t i = 0; i < N; i++) {
        // choose a pseudo-random mid
        lfs_ssize_t mid = (lfs_ssize_t)(
                TEST_PRNG(&prng) % lfs_max32(lfsr_mtree_weight(&lfs), 1));
        // fetch mdir
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        // choose a pseudo-random rid
        mdir.mid.rid = TEST_PRNG(&prng) % (mdir.u.m.weight+1);
        // choose to create or delete
        uint8_t op = (lfs_size_t)mdir.mid.rid == mdir.u.m.weight
                ? 0
                : TEST_PRNG(&prng) % 3;

        // force a compaction?
        if (FORCE_COMPACTION) {
            mdir.u.r.rbyd.eoff = -1;
            lfs.mroot.u.r.rbyd.eoff = -1;
        }

        // create
        if (op == 0) {
            // add to rbyd
            lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                    LFSR_ATTR(mdir.mid.rid, REG, +1,
                        BUF(&alphas[i % 26], 1)))) => 0;

            // make sure we can look up the new entry
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

            count += 1;

        // update
        } else if (op == 1) {
            // update rbyd
            lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                    LFSR_ATTR(mdir.mid.rid, REG, 0,
                        BUF(&alphas[i % 26], 1)))) => 0;

            // make sure we can look up the new entry
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

        // delete
        } else {
            lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                    LFSR_ATTR(mdir.mid.rid, RM, -1, NULL))) => 0;

            count -= 1;
        }
    }

    // try looking up each entry
    lfs_size_t count_ = 0;

    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;

        // drop should make sure we never have empty mdirs
        assert(lfsr_mtree_isinlined(&lfs) || mdir.u.m.weight > 0);

        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;

            count_ += 1;
        }
    }

    // the mtree is a bit difficult to simulate, but we can at least test
    // we ended up with the right number of entries
    assert(count_ == count);

    lfsr_unmount(&lfs) => 0;


    // check things stay sane after remount
    lfsr_mount(&lfs, CFG) => 0;

    // try looking up each entry
    count_ = 0;

    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;

        // drop should make sure we never have empty mdirs
        assert(lfsr_mtree_isinlined(&lfs) || mdir.u.m.weight > 0);

        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;

            count_ += 1;
        }
    }

    // the mtree is a bit difficult to simulate, but we can at least test
    // we ended up with the right number of entries
    assert(count_ == count);

    lfsr_unmount(&lfs) => 0;
'''


## Neighboring mdir updates ##

[cases.test_mtree_neighbor]
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // setup our neighbors
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)),
            LFSR_ATTR(1, REG, +1, BUF("b", 1)))) => 0;
    // this test only works if these all fit in the mroot
    assert(lfsr_mtree_isinlined(&lfs));

    lfsr_openedmdir_t left_neighbor  = {
            .mdir={.mid=LFSR_MID(0, 0), .u.m=lfs.mroot.u.m}};
    lfsr_openedmdir_t right_neighbor = {
            .mdir={.mid=LFSR_MID(0, 1), .u.m=lfs.mroot.u.m}};
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // insert a new entry, this should update our neighbors
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF("c", 1)))) => 0;

    // assert that our entry is still in the mtree
    assert(lfs.mroot.u.m.weight == 3);

    uint8_t buffer[1];
    lfsr_mdir_get(&lfs, &lfs.mroot, 1, LFSR_TAG_REG,
            buffer, 1) => 1;
    assert(memcmp(buffer, "c", 1) == 0);

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0);
    assert(left_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&left_neighbor.mdir.u.m, &lfs.mroot.u.m,
            sizeof(lfs.mroot.u.m)) == 0);
    assert(!lfsr_mdir_isdropped(&right_neighbor.mdir));
    assert(right_neighbor.mdir.mid.bid == 0);
    assert(right_neighbor.mdir.mid.rid == 2);
    assert(memcmp(&right_neighbor.mdir.u.m, &lfs.mroot.u.m,
            sizeof(lfs.mroot.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_remove_l]
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // setup our neighbors
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)),
            LFSR_ATTR(1, REG, +1, BUF("b", 1)))) => 0;
    // this test only works if these all fit in the mroot
    assert(lfsr_mtree_isinlined(&lfs));

    lfsr_openedmdir_t left_neighbor  = {
            .mdir={.mid=LFSR_MID(0, 0), .u.m=lfs.mroot.u.m}};
    lfsr_openedmdir_t right_neighbor = {
            .mdir={.mid=LFSR_MID(0, 1), .u.m=lfs.mroot.u.m}};
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // try removing our left entry
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // assert that an entry was removed
    assert(lfs.mroot.u.m.weight == 1);

    // assert that our neighbors were updated correctly
    assert(lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(!lfsr_mdir_isdropped(&right_neighbor.mdir));
    assert(right_neighbor.mdir.mid.bid == 0);
    assert(right_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&right_neighbor.mdir.u.m, &lfs.mroot.u.m,
            sizeof(lfs.mroot.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_remove_r]
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // setup our neighbors
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)),
            LFSR_ATTR(1, REG, +1, BUF("b", 1)))) => 0;
    // this test only works if these all fit in the mroot
    assert(lfsr_mtree_isinlined(&lfs));

    lfsr_openedmdir_t left_neighbor  = {
            .mdir={.mid=LFSR_MID(0, 0), .u.m=lfs.mroot.u.m}};
    lfsr_openedmdir_t right_neighbor = {
            .mdir={.mid=LFSR_MID(0, 1), .u.m=lfs.mroot.u.m}};
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // try removing our left entry
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, RM, -1, NULL))) => 0;

    // assert that an entry was removed
    assert(lfs.mroot.u.m.weight == 1);

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0);
    assert(left_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&left_neighbor.mdir.u.m, &lfs.mroot.u.m,
            sizeof(lfs.mroot.u.m)) == 0);
    assert(lfsr_mdir_isdropped(&right_neighbor.mdir));

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_uninline]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // setup our neighbors
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)),
            LFSR_ATTR(1, REG, +1, BUF("b", 1)))) => 0;
    // this test only works if these all fit in the mroot
    assert(lfsr_mtree_isinlined(&lfs));

    lfsr_openedmdir_t left_neighbor  = {
            .mdir={.mid=LFSR_MID(0, 0), .u.m=lfs.mroot.u.m}};
    lfsr_openedmdir_t right_neighbor = {
            .mdir={.mid=LFSR_MID(0, 1), .u.m=lfs.mroot.u.m}};
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // prepare mroot with a large attr so the next entry can not fit
    uint8_t buffer[SIZE];
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // create a large entry that needs to be uninlined (but not split!)
    memset(buffer, 'd', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 2);
    lfsr_mdir_get(&lfs, &mdir, 1, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "d", 1) == 0);

    // note that our current implementation splits here, which is suboptimal
    // but saves on code size
    lfsr_mdir_t msibling;
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &msibling) => 0;
    assert(msibling.u.m.weight == 1);

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0*lfsr_mbidweight(&lfs));
    assert(left_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&left_neighbor.mdir.u.m, &mdir.u.m,
            sizeof(mdir.u.m)) == 0);
    assert(!lfsr_mdir_isdropped(&right_neighbor.mdir));
    assert(right_neighbor.mdir.mid.bid == 1*lfsr_mbidweight(&lfs));
    assert(right_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&right_neighbor.mdir.u.m, &msibling.u.m,
            sizeof(msibling.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_uninline_split]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // setup our neighbors
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)),
            LFSR_ATTR(1, REG, +1, BUF("b", 1)))) => 0;
    // this test only works if these all fit in the mroot
    assert(lfsr_mtree_isinlined(&lfs));

    lfsr_openedmdir_t left_neighbor  = {
            .mdir={.mid=LFSR_MID(0, 0), .u.m=lfs.mroot.u.m}};
    lfsr_openedmdir_t right_neighbor = {
            .mdir={.mid=LFSR_MID(0, 1), .u.m=lfs.mroot.u.m}};
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // create 2 large entries that needs to be uninlined and split
    uint8_t buffer[SIZE];
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'd', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(2, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our entries are still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 2);
    lfsr_mdir_get(&lfs, &mdir, 1, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    lfsr_mdir_t msibling;
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &msibling) => 0;
    assert(msibling.u.m.weight == 2);
    lfsr_mdir_get(&lfs, &msibling, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "d", 1) == 0);

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0*lfsr_mbidweight(&lfs));
    assert(left_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&left_neighbor.mdir.u.m, &mdir.u.m,
            sizeof(mdir.u.m)) == 0);
    assert(!lfsr_mdir_isdropped(&right_neighbor.mdir));
    assert(right_neighbor.mdir.mid.bid == 1*lfsr_mbidweight(&lfs));
    assert(right_neighbor.mdir.mid.rid == 1);
    assert(memcmp(&right_neighbor.mdir.u.m, &msibling.u.m,
            sizeof(msibling.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_split]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'd', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // setup our neighbors
    //
    // note we do this after uninlining! this is because uninlining may
    // aggresively split the mtree if there are already neighbors in the mdir
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)),
            LFSR_ATTR(2, REG, +1, BUF("b", 1)))) => 0;
    // this test only works if these all fit in the mdir
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    assert(mdir.u.m.weight == 3);

    lfsr_openedmdir_t left_neighbor  = {
            .mdir={.mid=LFSR_MID(0, 0), .u.m=mdir.u.m}};
    lfsr_openedmdir_t right_neighbor = {
            .mdir={.mid=LFSR_MID(0, 2), .u.m=mdir.u.m}};
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // now add another large entry to the mdir, forcing a split
    memset(buffer, 'e', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(2, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;

    // assert mdir was split correctly
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot still has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 2);
    lfsr_mdir_get(&lfs, &mdir, 1, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "d", 1) == 0);

    lfsr_mdir_t msibling;
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &msibling) => 0;
    assert(msibling.u.m.weight == 2);
    lfsr_mdir_get(&lfs, &msibling, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "e", 1) == 0);

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0*lfsr_mbidweight(&lfs));
    assert(left_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&left_neighbor.mdir.u.m, &mdir.u.m,
            sizeof(mdir.u.m)) == 0);
    assert(!lfsr_mdir_isdropped(&right_neighbor.mdir));
    assert(right_neighbor.mdir.mid.bid == 1*lfsr_mbidweight(&lfs));
    assert(right_neighbor.mdir.mid.rid == 1);
    assert(memcmp(&right_neighbor.mdir.u.m, &msibling.u.m,
            sizeof(msibling.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // setup our neighbors
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)),
            LFSR_ATTR(1, REG, +1, BUF("b", 1)))) => 0;
    // this test only works if these all fit in the mroot
    assert(lfsr_mtree_isinlined(&lfs));

    lfsr_openedmdir_t left_neighbor  = {
            .mdir={.mid=LFSR_MID(0, 0), .u.m=lfs.mroot.u.m}};
    lfsr_openedmdir_t right_neighbor = {
            .mdir={.mid=LFSR_MID(0, 1), .u.m=lfs.mroot.u.m}};
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // prepare mroot with an attr
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact twice, this should extend the mroot
    lfsr_mdir_t old_mroot = lfs.mroot;

    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0);
    assert(left_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&left_neighbor.mdir.u.m, &lfs.mroot.u.m,
            sizeof(lfs.mroot.u.m)) == 0);
    assert(!lfsr_mdir_isdropped(&right_neighbor.mdir));
    assert(right_neighbor.mdir.mid.bid == 0);
    assert(right_neighbor.mdir.mid.rid == 1);
    assert(memcmp(&right_neighbor.mdir.u.m, &lfs.mroot.u.m,
            sizeof(lfs.mroot.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_relocate]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create an uninlined mdir
    uint8_t buffer[SIZE];
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'd', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // setup our neighbors
    //
    // note we do this after uninlining! this is because uninlining may
    // aggresively split the mtree if there are already neighbors in the mdir
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)),
            LFSR_ATTR(2, REG, +1, BUF("b", 1)))) => 0;
    // this test only works if these all fit in the mdir
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    assert(mdir.u.m.weight == 3);

    lfsr_openedmdir_t left_neighbor  = {
            .mdir={.mid=LFSR_MID(0, 0), .u.m=mdir.u.m}};
    lfsr_openedmdir_t right_neighbor = {
            .mdir={.mid=LFSR_MID(0, 2), .u.m=mdir.u.m}};
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // force mdir to compact twice, this should relocate
    lfsr_mdir_t old_mdir = mdir;

    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'e', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mdir.u.m.blocks, mdir.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "c", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 3);

    lfsr_mdir_get(&lfs, &mdir, 1, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "e", 1) == 0);

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0*lfsr_mbidweight(&lfs));
    assert(left_neighbor.mdir.mid.rid == 0);
    assert(memcmp(&left_neighbor.mdir.u.m, &mdir.u.m, sizeof(mdir.u.m)) == 0);
    assert(!lfsr_mdir_isdropped(&right_neighbor.mdir));
    assert(right_neighbor.mdir.mid.bid == 0*lfsr_mbidweight(&lfs));
    assert(right_neighbor.mdir.mid.rid == 2);
    assert(memcmp(&right_neighbor.mdir.u.m, &mdir.u.m, sizeof(mdir.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_middle_split]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    //// create a situation where we have 3 mdirs in our tree

    // first force mroot to uninlined+split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // we should now have 2 mdirs
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));

    // now force one of our siblings to split
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;

    // we should now have 3 mdirs
    assert(lfsr_mtree_weight(&lfs) == 3*lfsr_mbidweight(&lfs));


    //// Now test splitting updates mids correctly

    // setup our neighbors
    lfsr_openedmdir_t left_neighbor;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &left_neighbor.mdir) => 0;
    assert(left_neighbor.mdir.u.m.weight == 1);
    left_neighbor.mdir.mid.rid = 0;

    lfsr_openedmdir_t right_neighbor;
    lfsr_mtree_lookup(&lfs, LFSR_MID(2*lfsr_mbidweight(&lfs), -1), &right_neighbor.mdir) => 0;
    assert(right_neighbor.mdir.u.m.weight == 1);
    right_neighbor.mdir.mid.rid = 0;

    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // cause middle mdir to split
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    memset(buffer, 'd', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;

    // we should now have 4 mdirs
    assert(lfsr_mtree_weight(&lfs) == 4*lfsr_mbidweight(&lfs));

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0*lfsr_mbidweight(&lfs));
    assert(left_neighbor.mdir.mid.rid == 0);
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(memcmp(&left_neighbor.mdir.u.m, &mdir.u.m, sizeof(mdir.u.m)) == 0);

    assert(right_neighbor.mdir.mid.bid == 3*lfsr_mbidweight(&lfs));
    assert(right_neighbor.mdir.mid.rid == 0);
    lfsr_mtree_lookup(&lfs, LFSR_MID(3*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(memcmp(&right_neighbor.mdir.u.m, &mdir.u.m, sizeof(mdir.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_neighbor_middle_drop]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    //// create a situation where we have 3 mdirs in our tree

    // first force mroot to uninlined+split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // we should now have 2 mdirs
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));

    // now force one of our siblings to split
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    memset(buffer, 'c', SIZE);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mdir to compact
    mdir.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &mdir, NULL, 0) => 0;

    // we should now have 3 mdirs
    assert(lfsr_mtree_weight(&lfs) == 3*lfsr_mbidweight(&lfs));


    //// Now test dropping updates mids correctly

    // setup our neighbors
    lfsr_openedmdir_t left_neighbor;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &left_neighbor.mdir) => 0;
    assert(left_neighbor.mdir.u.m.weight == 1);
    left_neighbor.mdir.mid.rid = 0;

    lfsr_openedmdir_t right_neighbor;
    lfsr_mtree_lookup(&lfs, LFSR_MID(2*lfsr_mbidweight(&lfs), -1), &right_neighbor.mdir) => 0;
    assert(right_neighbor.mdir.u.m.weight == 1);
    right_neighbor.mdir.mid.rid = 0;

    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_addopened(&lfs, LFS_TYPE_REG, &right_neighbor);

    // cause middle mdir to drop 
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // we should now have 2 mdirs
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));

    // assert that our neighbors were updated correctly
    assert(!lfsr_mdir_isdropped(&left_neighbor.mdir));
    assert(left_neighbor.mdir.mid.bid == 0*lfsr_mbidweight(&lfs));
    assert(left_neighbor.mdir.mid.rid == 0);
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(memcmp(&left_neighbor.mdir.u.m, &mdir.u.m, sizeof(mdir.u.m)) == 0);

    assert(!lfsr_mdir_isdropped(&right_neighbor.mdir));
    assert(right_neighbor.mdir.mid.bid == 1*lfsr_mbidweight(&lfs));
    assert(right_neighbor.mdir.mid.rid == 0);
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(memcmp(&right_neighbor.mdir.u.m, &mdir.u.m, sizeof(mdir.u.m)) == 0);

    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &left_neighbor);
    lfsr_mdir_removeopened(&lfs, LFS_TYPE_REG, &right_neighbor);
    lfsr_unmount(&lfs) => 0;
'''


## mtree traversal ##

# test specific corner cases
[cases.test_mtree_traversal]
defines.VALIDATE = [false, true]
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // insert a new entry, this should update our neighbors
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF("a", 1)))) => 0;

    // assert that our entry is still in the mtree
    assert(lfs.mroot.u.m.weight == 1);

    uint8_t buffer[1];
    lfsr_mdir_get(&lfs, &lfs.mroot, 0, LFSR_TAG_REG,
            buffer, 1) => 1;
    assert(memcmp(buffer, "a", 1) == 0);

    // test that we can traverse the tree, keeping track of all blocks we see
    uint8_t *seen = malloc((BLOCK_COUNT+7)/8);
    memset(seen, 0, (BLOCK_COUNT+7)/8);

    lfsr_mtree_traversal_t traversal = LFSR_MTREE_TRAVERSAL(
            VALIDATE ? LFSR_MTREE_TRAVERSAL_VALIDATE : 0);

    for (lfs_block_t i = 0;; i++) {
        // a bit hacky, but this catches infinite loops
        assert(i < 2*1);

        lfsr_mid_t mid_;
        lfsr_tag_t tag_;
        lfsr_data_t data_;
        int err = lfsr_mtree_traversal_next(&lfs, &traversal,
                &mid_, &tag_, &data_);
        assert(!err || err == LFS_ERR_NOENT);
        if (err == LFS_ERR_NOENT) {
            break;
        }

        if (tag_ == LFSR_TAG_BTREE) {
            lfsr_rbyd_t *branch = (lfsr_rbyd_t *)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x btree 0x%x.%x\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    branch->block, branch->trunk);

            // keep track of seen blocks
            seen[branch->block / 8] |= 1 << (branch->block % 8);
        } else if (tag_ == LFSR_TAG_MDIR) {
            lfsr_mdir_t *mdir = (lfsr_mdir_t*)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x mdir 0x{%x,%x}\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    mdir->u.m.blocks[0], mdir->u.m.blocks[1]);

            // keep track of seen blocks
            seen[mdir->u.m.blocks[1] / 8] |= 1 << (mdir->u.m.blocks[1] % 8);
            seen[mdir->u.m.blocks[0] / 8] |= 1 << (mdir->u.m.blocks[0] % 8);
        } else {
            // this shouldn't happen
            printf("traversal: %d.%d 0x%x %d\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    lfsr_data_size(&data_));
            assert(false);
        }
    }

    // if traversal worked, we should be able to clobber all other blocks
    uint8_t buffer_[BLOCK_SIZE];
    memset(buffer_, 0xcc, BLOCK_SIZE);
    for (lfs_block_t block = 0; block < BLOCK_COUNT; block++) {
        if (!(seen[block / 8] & (1 << (block % 8)))) {
            CFG->erase(CFG, block) => 0;
            CFG->prog(CFG, block, 0, buffer_, BLOCK_SIZE) => 0;
        }
    }
    free(seen);

    // and the tree should still work

    // assert that our entry is still in the mtree
    assert(lfs.mroot.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &lfs.mroot, 0, LFSR_TAG_REG,
            buffer, 1) => 1;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_traversal_uninline]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
defines.VALIDATE = [false, true]
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // prepare mroot with a large attr so the next entry can not fit
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // create a large entry that needs to be uninlined (but not split!)
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    // test that we can traverse the tree, keeping track of all blocks we see
    uint8_t *seen = malloc((BLOCK_COUNT+7)/8);
    memset(seen, 0, (BLOCK_COUNT+7)/8);

    lfsr_mtree_traversal_t traversal = LFSR_MTREE_TRAVERSAL(
            VALIDATE ? LFSR_MTREE_TRAVERSAL_VALIDATE : 0);

    for (lfs_block_t i = 0;; i++) {
        // a bit hacky, but this catches infinite loops
        assert(i < 2*2);

        lfsr_mid_t mid_;
        lfsr_tag_t tag_;
        lfsr_data_t data_;
        int err = lfsr_mtree_traversal_next(&lfs, &traversal,
                &mid_, &tag_, &data_);
        assert(!err || err == LFS_ERR_NOENT);
        if (err == LFS_ERR_NOENT) {
            break;
        }

        if (tag_ == LFSR_TAG_BTREE) {
            lfsr_rbyd_t *branch = (lfsr_rbyd_t *)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x btree 0x%x.%x\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    branch->block, branch->trunk);

            // keep track of seen blocks
            seen[branch->block / 8] |= 1 << (branch->block % 8);
        } else if (tag_ == LFSR_TAG_MDIR) {
            lfsr_mdir_t *mdir = (lfsr_mdir_t*)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x mdir 0x{%x,%x}\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    mdir->u.m.blocks[0], mdir->u.m.blocks[1]);

            // keep track of seen blocks
            seen[mdir->u.m.blocks[1] / 8] |= 1 << (mdir->u.m.blocks[1] % 8);
            seen[mdir->u.m.blocks[0] / 8] |= 1 << (mdir->u.m.blocks[0] % 8);
        } else {
            // this shouldn't happen
            printf("traversal: %d.%d 0x%x %d\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    lfsr_data_size(&data_));
            assert(false);
        }
    }

    // if traversal worked, we should be able to clobber all other blocks
    uint8_t buffer_[BLOCK_SIZE];
    memset(buffer_, 0xcc, BLOCK_SIZE);
    for (lfs_block_t block = 0; block < BLOCK_COUNT; block++) {
        if (!(seen[block / 8] & (1 << (block % 8)))) {
            CFG->erase(CFG, block) => 0;
            CFG->prog(CFG, block, 0, buffer_, BLOCK_SIZE) => 0;
        }
    }
    free(seen);

    // and the tree should still work

    // assert mdir was unininlined correctly
    assert(lfsr_mtree_weight(&lfs) == 1*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    // assert that our entry is still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);

    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_traversal_split]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
defines.VALIDATE = [false, true]
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create 2 large entries that needs to be uninlined and split
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, REG, +1, BUF(buffer, SIZE)))) => 0;

    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(1, REG, +1, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our entries are still in the mtree
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_mdir_t msibling;
    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &msibling) => 0;
    assert(msibling.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &msibling, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    // test that we can traverse the tree, keeping track of all blocks we see
    uint8_t *seen = malloc((BLOCK_COUNT+7)/8);
    memset(seen, 0, (BLOCK_COUNT+7)/8);

    lfsr_mtree_traversal_t traversal = LFSR_MTREE_TRAVERSAL(
            VALIDATE ? LFSR_MTREE_TRAVERSAL_VALIDATE : 0);

    for (lfs_block_t i = 0;; i++) {
        // a bit hacky, but this catches infinite loops
        assert(i < 2*3);

        lfsr_mid_t mid_;
        lfsr_tag_t tag_;
        lfsr_data_t data_;
        int err = lfsr_mtree_traversal_next(&lfs, &traversal,
                &mid_, &tag_, &data_);
        assert(!err || err == LFS_ERR_NOENT);
        if (err == LFS_ERR_NOENT) {
            break;
        }

        if (tag_ == LFSR_TAG_BTREE) {
            lfsr_rbyd_t *branch = (lfsr_rbyd_t *)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x btree 0x%x.%x\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    branch->block, branch->trunk);

            // keep track of seen blocks
            seen[branch->block / 8] |= 1 << (branch->block % 8);
        } else if (tag_ == LFSR_TAG_MDIR) {
            lfsr_mdir_t *mdir = (lfsr_mdir_t*)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x mdir 0x{%x,%x}\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    mdir->u.m.blocks[0], mdir->u.m.blocks[1]);

            // keep track of seen blocks
            seen[mdir->u.m.blocks[1] / 8] |= 1 << (mdir->u.m.blocks[1] % 8);
            seen[mdir->u.m.blocks[0] / 8] |= 1 << (mdir->u.m.blocks[0] % 8);
        } else {
            // this shouldn't happen
            printf("traversal: %d.%d 0x%x %d\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    lfsr_data_size(&data_));
            assert(false);
        }
    }

    // if traversal worked, we should be able to clobber all other blocks
    uint8_t buffer_[BLOCK_SIZE];
    memset(buffer_, 0xcc, BLOCK_SIZE);
    for (lfs_block_t block = 0; block < BLOCK_COUNT; block++) {
        if (!(seen[block / 8] & (1 << (block % 8)))) {
            CFG->erase(CFG, block) => 0;
            CFG->prog(CFG, block, 0, buffer_, BLOCK_SIZE) => 0;
        }
    }
    free(seen);

    // and the tree should still work

    // assert mdirs were unininlined and split
    assert(lfsr_mtree_weight(&lfs) == 2*lfsr_mbidweight(&lfs));
    // assert mroot now has no entries
    assert(lfs.mroot.u.m.weight == 0);

    // assert that our entries are still in the mtree
    lfsr_mtree_lookup(&lfs, LFSR_MID(0*lfsr_mbidweight(&lfs), -1), &mdir) => 0;
    assert(mdir.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &mdir, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "a", 1) == 0);

    lfsr_mtree_lookup(&lfs, LFSR_MID(1*lfsr_mbidweight(&lfs), -1), &msibling) => 0;
    assert(msibling.u.m.weight == 1);
    lfsr_mdir_get(&lfs, &msibling, 0, LFSR_TAG_REG,
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_traversal_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
defines.VALIDATE = [false, true]
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // prepare mroot with an attr
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact twice, this should extend the mroot
    lfsr_mdir_t old_mroot = lfs.mroot;

    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    // test that we can traverse the tree, keeping track of all blocks we see
    uint8_t *seen = malloc((BLOCK_COUNT+7)/8);
    memset(seen, 0, (BLOCK_COUNT+7)/8);

    lfsr_mtree_traversal_t traversal = LFSR_MTREE_TRAVERSAL(
            VALIDATE ? LFSR_MTREE_TRAVERSAL_VALIDATE : 0);

    for (lfs_block_t i = 0;; i++) {
        // a bit hacky, but this catches infinite loops
        assert(i < 2*3);

        lfsr_mid_t mid_;
        lfsr_tag_t tag_;
        lfsr_data_t data_;
        int err = lfsr_mtree_traversal_next(&lfs, &traversal,
                &mid_, &tag_, &data_);
        assert(!err || err == LFS_ERR_NOENT);
        if (err == LFS_ERR_NOENT) {
            break;
        }

        if (tag_ == LFSR_TAG_BTREE) {
            lfsr_rbyd_t *branch = (lfsr_rbyd_t *)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x btree 0x%x.%x\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    branch->block, branch->trunk);

            // keep track of seen blocks
            seen[branch->block / 8] |= 1 << (branch->block % 8);
        } else if (tag_ == LFSR_TAG_MDIR) {
            lfsr_mdir_t *mdir = (lfsr_mdir_t*)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x mdir 0x{%x,%x}\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    mdir->u.m.blocks[0], mdir->u.m.blocks[1]);

            // keep track of seen blocks
            seen[mdir->u.m.blocks[1] / 8] |= 1 << (mdir->u.m.blocks[1] % 8);
            seen[mdir->u.m.blocks[0] / 8] |= 1 << (mdir->u.m.blocks[0] % 8);
        } else {
            // this shouldn't happen
            printf("traversal: %d.%d 0x%x %d\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    lfsr_data_size(&data_));
            assert(false);
        }
    }

    // if traversal worked, we should be able to clobber all other blocks
    uint8_t buffer_[BLOCK_SIZE];
    memset(buffer_, 0xcc, BLOCK_SIZE);
    for (lfs_block_t block = 0; block < BLOCK_COUNT; block++) {
        if (!(seen[block / 8] & (1 << (block % 8)))) {
            CFG->erase(CFG, block) => 0;
            CFG->prog(CFG, block, 0, buffer_, BLOCK_SIZE) => 0;
        }
    }
    free(seen);

    // and the tree should still work

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;
'''

# larger traversal tests
[cases.test_mtree_traversal_many]
defines.N = [5, 10, 20, 40, 80, 160, 320]
defines.VALIDATE = [false, true]
defines.FORCE_COMPACTION = [false, true]
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // create entries
    lfsr_mdir_t mdir;
    lfsr_mtree_lookup(&lfs, LFSR_MID(lfs_smax32(lfsr_mtree_weight(&lfs)-1, 0), -1),
            &mdir) => 0;

    mdir.mid.rid = 0;
    for (lfs_size_t i = 0; i < N; i++) {
        // force a compaction?
        if (FORCE_COMPACTION) {
            mdir.u.r.rbyd.eoff = -1;
            lfs.mroot.u.r.rbyd.eoff = -1;
        }

        lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                LFSR_ATTR(mdir.mid.rid, REG, +1,
                    BUF(&alphas[i % 26], 1)))) => 0;

        uint8_t buffer[4];
        lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                buffer, 4) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

        mdir.mid.rid += 1;
    }

    // try looking up each entry
    lfs_size_t i = 0;
    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
            i += 1;
        }
    }
    assert(i == N);

    // test that we can traverse the tree, keeping track of all blocks we see
    uint8_t *seen = malloc((BLOCK_COUNT+7)/8);
    memset(seen, 0, (BLOCK_COUNT+7)/8);

    lfsr_mtree_traversal_t traversal = LFSR_MTREE_TRAVERSAL(
            VALIDATE ? LFSR_MTREE_TRAVERSAL_VALIDATE : 0);

    for (lfs_block_t i = 0;; i++) {
        // a bit hacky, but this catches infinite loops
        assert(i < 2*(1+N));

        lfsr_mid_t mid_;
        lfsr_tag_t tag_;
        lfsr_data_t data_;
        int err = lfsr_mtree_traversal_next(&lfs, &traversal,
                &mid_, &tag_, &data_);
        assert(!err || err == LFS_ERR_NOENT);
        if (err == LFS_ERR_NOENT) {
            break;
        }

        if (tag_ == LFSR_TAG_BTREE) {
            lfsr_rbyd_t *branch = (lfsr_rbyd_t *)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x btree 0x%x.%x\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    branch->block, branch->trunk);

            // keep track of seen blocks
            seen[branch->block / 8] |= 1 << (branch->block % 8);
        } else if (tag_ == LFSR_TAG_MDIR) {
            lfsr_mdir_t *mdir = (lfsr_mdir_t*)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x mdir 0x{%x,%x}\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    mdir->u.m.blocks[0], mdir->u.m.blocks[1]);

            // keep track of seen blocks
            seen[mdir->u.m.blocks[1] / 8] |= 1 << (mdir->u.m.blocks[1] % 8);
            seen[mdir->u.m.blocks[0] / 8] |= 1 << (mdir->u.m.blocks[0] % 8);
        } else {
            // this shouldn't happen
            printf("traversal: %d.%d 0x%x %d\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    lfsr_data_size(&data_));
            assert(false);
        }
    }

    // if traversal worked, we should be able to clobber all other blocks
    uint8_t buffer_[BLOCK_SIZE];
    memset(buffer_, 0xcc, BLOCK_SIZE);
    for (lfs_block_t block = 0; block < BLOCK_COUNT; block++) {
        if (!(seen[block / 8] & (1 << (block % 8)))) {
            CFG->erase(CFG, block) => 0;
            CFG->prog(CFG, block, 0, buffer_, BLOCK_SIZE) => 0;
        }
    }
    free(seen);

    // and the tree should still work

    // try looking up each entry
    i = 0;
    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;
            assert(memcmp(buffer, &alphas[i % 26], 1) == 0);
            i += 1;
        }
    }
    assert(i == N);

    lfsr_unmount(&lfs) => 0;
'''

[cases.test_mtree_traversal_fuzz]
defines.N = [5, 10, 20, 40, 80, 160]
defines.VALIDATE = [false, true]
defines.FORCE_COMPACTION = [false, true]
defines.SEED = 'range(100)'
in = 'lfs.c'
code = '''
    const char *alphas = "abcdefghijklmnopqrstuvwxyz";

    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);
    // remove root dstart for now
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(0, RM, -1, NULL))) => 0;

    // at least keep track of the number of entries we expect
    lfs_size_t count = 0;

    uint32_t prng = SEED;
    for (lfs_size_t i = 0; i < N; i++) {
        // choose a pseudo-random mid
        lfs_ssize_t mid = (lfs_ssize_t)(
                TEST_PRNG(&prng) % lfs_max32(lfsr_mtree_weight(&lfs), 1));
        // fetch mdir
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        // choose a pseudo-random rid
        mdir.mid.rid = TEST_PRNG(&prng) % (mdir.u.m.weight+1);

        // force a compaction?
        if (FORCE_COMPACTION) {
            mdir.u.r.rbyd.eoff = -1;
            lfs.mroot.u.r.rbyd.eoff = -1;
        }

        // add to rbyd, potentially splitting the mdir
        lfsr_mdir_commit(&lfs, &mdir, LFSR_ATTRS(
                LFSR_ATTR(mdir.mid.rid, REG, +1,
                    BUF(&alphas[i % 26], 1)))) => 0;

        // make sure we can look up the new entry
        uint8_t buffer[4];
        lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                buffer, 4) => 1;
        assert(memcmp(buffer, &alphas[i % 26], 1) == 0);

        count += 1;
    }

    // try looking up each entry
    lfs_size_t count_ = 0;

    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;

            count_ += 1;
        }
    }

    // the mtree is a bit difficult to simulate, but we can at least test
    // we ended up with the right number of entries
    assert(count_ == count);

    // test that we can traverse the tree, keeping track of all blocks
    // we see
    uint8_t *seen = malloc((BLOCK_COUNT+7)/8);
    memset(seen, 0, (BLOCK_COUNT+7)/8);

    lfsr_mtree_traversal_t traversal = LFSR_MTREE_TRAVERSAL(
            VALIDATE ? LFSR_MTREE_TRAVERSAL_VALIDATE : 0);

    for (lfs_block_t i = 0;; i++) {
        // a bit hacky, but this catches infinite loops
        assert(i < 2*(1+N));

        lfsr_mid_t mid_;
        lfsr_tag_t tag_;
        lfsr_data_t data_;
        int err = lfsr_mtree_traversal_next(&lfs, &traversal,
                &mid_, &tag_, &data_);
        assert(!err || err == LFS_ERR_NOENT);
        if (err == LFS_ERR_NOENT) {
            break;
        }

        if (tag_ == LFSR_TAG_BTREE) {
            lfsr_rbyd_t *branch = (lfsr_rbyd_t *)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x btree 0x%x.%x\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    branch->block, branch->trunk);

            // keep track of seen blocks
            seen[branch->block / 8] |= 1 << (branch->block % 8);
        } else if (tag_ == LFSR_TAG_MDIR) {
            lfsr_mdir_t *mdir = (lfsr_mdir_t*)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x mdir 0x{%x,%x}\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    mdir->u.m.blocks[0], mdir->u.m.blocks[1]);

            // keep track of seen blocks
            seen[mdir->u.m.blocks[1] / 8] |= 1 << (mdir->u.m.blocks[1] % 8);
            seen[mdir->u.m.blocks[0] / 8] |= 1 << (mdir->u.m.blocks[0] % 8);
        } else {
            // this shouldn't happen
            printf("traversal: %d.%d 0x%x %d\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    lfsr_data_size(&data_));
            assert(false);
        }
    }

    // if traversal worked, we should be able to clobber all other blocks
    uint8_t buffer_[BLOCK_SIZE];
    memset(buffer_, 0xcc, BLOCK_SIZE);
    for (lfs_block_t block = 0; block < BLOCK_COUNT; block++) {
        if (!(seen[block / 8] & (1 << (block % 8)))) {
            CFG->erase(CFG, block) => 0;
            CFG->prog(CFG, block, 0, buffer_, BLOCK_SIZE) => 0;
        }
    }
    free(seen);

    // and the tree should still work

    // try looking up each entry
    count_ = 0;

    for (lfs_ssize_t mid = 0;
            mid < lfs_smax32(lfsr_mtree_weight(&lfs), 1);
            mid += lfsr_mbidweight(&lfs)) {
        lfsr_mdir_t mdir;
        lfsr_mtree_lookup(&lfs, LFSR_MID(mid, -1), &mdir) => 0;
        for (mdir.mid.rid = 0;
                mdir.mid.rid < (lfs_ssize_t)mdir.u.m.weight;
                mdir.mid.rid++) {
            uint8_t buffer[4];
            lfsr_mdir_get(&lfs, &mdir, mdir.mid.rid, LFSR_TAG_REG,
                    buffer, 4) => 1;

            count_ += 1;
        }
    }

    // the mtree is a bit difficult to simulate, but we can at least test
    // we ended up with the right number of entries
    assert(count_ == count);

    lfsr_unmount(&lfs) => 0;
'''


## Cycle detection? ##

# test that our cycle detector at least works in common cases
[cases.test_mtree_traversal_mroot_cycle]
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);

    uint8_t buffer[LFSR_MDIR_DSIZE];
    lfs_ssize_t d = lfsr_mdir_todisk(&lfs, LFSR_MDIR_MROOTANCHOR, buffer);
    assert(d >= 0);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, MROOT, 0, BUF(buffer, d)))) => 0;

    // technically, cycle detection only needs to work when we're validating
    lfsr_mtree_traversal_t traversal = LFSR_MTREE_TRAVERSAL(
            LFSR_MTREE_TRAVERSAL_VALIDATE);

    for (lfs_block_t i = 0;; i++) {
        // assert that we detect the cycle in a reasonable number of iterations
        assert(i < 1024);

        lfsr_mid_t mid_;
        lfsr_tag_t tag_;
        lfsr_data_t data_;
        int err = lfsr_mtree_traversal_next(&lfs, &traversal,
                &mid_, &tag_, &data_);
        assert(!err || err == LFS_ERR_CORRUPT);
        if (err == LFS_ERR_CORRUPT) {
            break;
        }

        if (tag_ == LFSR_TAG_BTREE) {
            lfsr_rbyd_t *branch = (lfsr_rbyd_t *)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x btree 0x%x.%x\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    branch->block, branch->trunk);
        } else if (tag_ == LFSR_TAG_MDIR) {
            lfsr_mdir_t *mdir = (lfsr_mdir_t*)data_.u.b.buffer;
            printf("traversal: %d.%d 0x%x mdir 0x{%x,%x}\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    mdir->u.m.blocks[0], mdir->u.m.blocks[1]);
        } else {
            // this shouldn't happen
            printf("traversal: %d.%d 0x%x %d\n",
                    mid_.bid,
                    mid_.rid,
                    tag_,
                    lfsr_data_size(&data_));
            assert(false);
        }
    }

    lfsr_unmount(&lfs) => 0;
'''


## Magic consistency ##

# make sure our magic string ("littlefs") shows up in the same place (off=8)
[cases.test_mtree_magic]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;

    // check our magic string
    //
    // note if we lose power we may not have the magic string in both blocks!
    // but we don't lose power in this test so we can assert the magic string
    // is present in both
    uint8_t magic[lfs_max(16, READ_SIZE)];
    CFG->read(CFG, 0, 0, magic, lfs_max(16, READ_SIZE)) => 0;
    assert(memcmp(&magic[8], "littlefs", 8) == 0);
    CFG->read(CFG, 1, 0, magic, lfs_max(16, READ_SIZE)) => 0;
    assert(memcmp(&magic[8], "littlefs", 8) == 0);
'''

[cases.test_mtree_magic_extend]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);

    // prepare mroot with an attr
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact twice, this should extend the mroot
    lfsr_mdir_t old_mroot = lfs.mroot;

    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check our magic string
    //
    // note if we lose power we may not have the magic string in both blocks!
    // but we don't lose power in this test so we can assert the magic string
    // is present in both
    uint8_t magic[lfs_max(16, READ_SIZE)];
    CFG->read(CFG, 0, 0, magic, lfs_max(16, READ_SIZE)) => 0;
    assert(memcmp(&magic[8], "littlefs", 8) == 0);
    CFG->read(CFG, 1, 0, magic, lfs_max(16, READ_SIZE)) => 0;
    assert(memcmp(&magic[8], "littlefs", 8) == 0);
'''

[cases.test_mtree_magic_extend_twice]
# this should be set so only one entry can fit in a metadata block
defines.SIZE = 'BLOCK_SIZE / 4'
# make it so blocks relocate every two compacts
defines.BLOCK_CYCLES = 2
# force our block to compact by setting prog_size=block_size, we don't have
# any way to indirectly force the intermediary mroots to compact otherwise
defines.PROG_SIZE = 'BLOCK_SIZE'
in = 'lfs.c'
code = '''
    lfs_t lfs;
    lfsr_format(&lfs, CFG) => 0;
    lfsr_mount(&lfs, CFG) => 0;
    lfs_alloc_ack(&lfs);

    // prepare mroot with an attr
    uint8_t buffer[SIZE];
    memset(buffer, 'a', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // force mroot to compact 2x2 times, this should extend the mroot twice
    lfsr_mdir_t old_mroot = lfs.mroot;

    for (int i = 0; i < 4; i++) {
        lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
        lfsr_mdir_commit(&lfs, &lfs.mroot, NULL, 0) => 0;
    }
    lfs.mroot.u.r.rbyd.eoff = BLOCK_SIZE;
    memset(buffer, 'b', SIZE);
    lfsr_mdir_commit(&lfs, &lfs.mroot, LFSR_ATTRS(
            LFSR_ATTR(-1, UATTR(1), 0, BUF(buffer, SIZE)))) => 0;

    // assert we relocated
    assert(lfsr_mdir_cmp(old_mroot.u.m.blocks, lfs.mroot.u.m.blocks) != 0);

    // assert that our attr is still in the mroot
    lfsr_mdir_get(&lfs, &lfs.mroot, -1, LFSR_TAG_UATTR(1),
            buffer, SIZE) => SIZE;
    assert(memcmp(buffer, "b", 1) == 0);

    lfsr_unmount(&lfs) => 0;


    // check our magic string
    //
    // note if we lose power we may not have the magic string in both blocks!
    // but we don't lose power in this test so we can assert the magic string
    // is present in both
    uint8_t magic[lfs_max(16, READ_SIZE)];
    CFG->read(CFG, 0, 0, magic, lfs_max(16, READ_SIZE)) => 0;
    assert(memcmp(&magic[8], "littlefs", 8) == 0);
    CFG->read(CFG, 1, 0, magic, lfs_max(16, READ_SIZE)) => 0;
    assert(memcmp(&magic[8], "littlefs", 8) == 0);
'''