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Dropped msprouts/single mptr representation

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I mean, what does the single mptr representation get us anyways?

A slightly smaller filesystem when metadata doesn't _quite_ fit in the
mroot, but fits in a single mdir? The only difference between the two is
the filesystem config, which really shouldn't be _that_ large:

  mmoss:         msprout:       mtree:
   .--------.     .--------.     .--------.
  .| mroot  |    .| mroot  |    .| mroot  |
  || config |    || config |    || config |
  || dir /  |    || mptr   |    || mptr   |
  |'--------'    |'---|----'    |'---|----'
  '--------'     '----|---'     '----|---'
                      v              v
                  .--------.     .--------.
                 .| mdir   |     | mtree  |
                 || mptr   |     | mptr   |
                 ||        |     |   |    |
                 |'--------'     '---|----'
                 '--------'          v
                                 .--------.
                                .| mdir   |
                                || mptr   |
                                ||        |
                                |'--------'
                                '--------'

Unlike the theoretical mshrub representation, which we've already given
up on, msprouts _don't_ require a significant code cost to implement.
But if they offer little value, why keep them around? Every code cost is
code cost.

---

This drops msprout support, saving a bit of code:

           code          stack          ctx
  before: 38508           2624          640
  after:  38340 (-0.4%)   2624 (+0.0%)  640 (+0.0%)

This also clears the LFSR_RCOMPAT_MSPROUT flag, allowing for msprouts to
be possibly reintroduced in the future.

But I don't really see any motivation for msprouts, even if you don't
care about code size, so I suspect this will just be a dead bit from now
on...
This commit is contained in:
Christopher Haster
2025-01-29 15:08:40 -06:00
parent 415e6325d1
commit 4a7e447051
1 changed files with 23 additions and 62 deletions
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lfs.c
+23 -62
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@@ -7475,8 +7475,6 @@ static inline int lfsr_mtree_cmp(
return a->u.weight - b->u.weight;
} else if (lfsr_mtree_isnull(a)) {
return 0;
} else if (lfsr_mtree_ismptr(a)) {
return lfsr_mptr_cmp(a->u.mptr.blocks, b->u.mptr.blocks);
} else {
return lfsr_btree_cmp(&a->u.btree, &b->u.btree);
}
@@ -7504,11 +7502,6 @@ static int lfsr_mtree_lookup(lfs_t *lfs, lfsr_smid_t mid,
lfsr_mdir_sync(mdir_, &lfs->mroot);
return 0;
// looking up direct mdir?
} else if (lfsr_mtree_ismptr(&lfs->mtree)) {
// fetch mdir
return lfsr_mdir_fetch(lfs, mdir_, mid, lfs->mtree.u.mptr.blocks);
// look up mdir in actual mtree
} else {
lfsr_bid_t bid;
@@ -8636,7 +8629,7 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
}
// new mtree?
if (lfsr_mtree_ismptr(&lfs->mtree)) {
if (lfsr_mtree_weight_(&lfs->mtree) == 0) {
lfsr_btree_init(&mtree_.u.btree);
uint8_t mdir_buf[2*LFSR_MPTR_DSIZE];
@@ -8702,9 +8695,8 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
dropped:;
mdelta = -(1 << lfs->mdir_bits);
// we should never drop a direct mdir, because we always have our
// root bookmark
LFS_ASSERT(!lfsr_mtree_ismptr(&lfs->mtree));
// how can we drop if we have no mtree?
LFS_ASSERT(lfsr_mtree_weight_(&lfs->mtree) != 0);
// mark as unerased in case of failure
lfs->mtree.u.btree.eoff = -1;
@@ -8730,16 +8722,26 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
relocated:;
// new mtree?
if (lfsr_mtree_ismptr(&lfs->mtree)) {
lfsr_mtree_frommptr(&mtree_,
mdir_[0].rbyd.blocks,
1 << lfs->mdir_bits);
if (lfsr_mtree_weight_(&lfs->mtree) == 0) {
lfsr_btree_init(&mtree_.u.btree);
uint8_t mdir_buf[LFSR_MPTR_DSIZE];
err = lfsr_btree_commit(lfs, &mtree_.u.btree,
0, LFSR_RATS(
LFSR_RAT(
LFSR_TAG_MDIR, +(1 << lfs->mdir_bits),
LFSR_DATA_MPTR(
mdir_[0].rbyd.blocks,
mdir_buf))));
if (err) {
goto failed;
}
// update our mtree
} else {
// mark as unerased in case of failure
lfs->mtree.u.btree.eoff = -1;
// update our mtree
uint8_t mdir_buf[LFSR_MPTR_DSIZE];
err = lfsr_btree_commit(lfs, &mtree_.u.btree,
lfsr_mid_bid(lfs, mdir->mid), LFSR_RATS(
@@ -8801,13 +8803,9 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
uint8_t mtree_buf[LFS_MAX(LFSR_MPTR_DSIZE, LFSR_BTREE_DSIZE)];
err = lfsr_mdir_commit_(lfs, &mroot_, -2, 0, NULL,
-1, LFSR_RATS(
(lfsr_mtree_ismptr(&mtree_))
? LFSR_RAT(
LFSR_TAG_SUB | LFSR_TAG_MDIR, 0,
LFSR_DATA_MPTR(mtree_.u.mptr.blocks, mtree_buf))
: LFSR_RAT(
LFSR_TAG_SUB | LFSR_TAG_MTREE, 0,
LFSR_DATA_BTREE(&mtree_.u.btree, mtree_buf)),
LFSR_RAT(
LFSR_TAG_SUB | LFSR_TAG_MTREE, 0,
LFSR_DATA_BTREE(&mtree_.u.btree, mtree_buf)),
// were we committing to the mroot? include any -1 rats
(mdir->mid == -1)
? LFSR_RAT_RATS(
@@ -9128,13 +9126,6 @@ static int lfsr_mtree_namelookup(lfs_t *lfs,
// treat inlined mdir as mid=0
mdir.mid = 0;
// direct mdir?
} else if (lfsr_mtree_ismptr(&lfs->mtree)) {
int err = lfsr_mdir_fetch(lfs, &mdir, 0, lfs->mtree.u.mptr.blocks);
if (err) {
return err;
}
// lookup name in actual mtree
} else {
lfsr_bid_t bid;
@@ -9404,7 +9395,7 @@ static int lfsr_mtree_traverse_(lfs_t *lfs, lfsr_traversal_t *t,
}
return 0;
// traverse the mroot chain, checking for mroot/mtree/mdir
// traverse the mroot chain, checking for mroots/mtrees
case LFSR_TSTATE_MROOTCHAIN:;
// lookup mroot, if we find one this is not the active mroot
lfsr_tag_t tag;
@@ -9412,7 +9403,7 @@ static int lfsr_mtree_traverse_(lfs_t *lfs, lfsr_traversal_t *t,
err = lfsr_mdir_sublookup(lfs, &t->o.o.mdir, LFSR_TAG_STRUCT,
&tag, &data);
if (err) {
// if we have no mtree/mdir (inlined mdir), we need to
// if we have no mtree (inlined mdir), we need to
// traverse any files in our mroot next
if (err == LFS_ERR_NOENT) {
t->o.o.mdir.mid = 0;
@@ -9463,27 +9454,6 @@ static int lfsr_mtree_traverse_(lfs_t *lfs, lfsr_traversal_t *t,
}
return 0;
// found an mdir?
} else if (tag == LFSR_TAG_MDIR) {
// fetch this mdir
err = lfsr_data_fetchmdir(lfs, &data, 0,
&t->o.o.mdir);
if (err) {
return err;
}
// transition to traversing the mdir
t->o.o.flags = lfsr_t_settstate(t->o.o.flags,
LFSR_TSTATE_MDIR);
if (tag_) {
*tag_ = LFSR_TAG_MDIR;
}
if (bptr_) {
bptr_->data.u.buffer = (const uint8_t*)&t->o.o.mdir;
}
return 0;
// found an mtree?
} else if (tag == LFSR_TAG_MTREE) {
// fetch the root of the mtree
@@ -13745,7 +13715,6 @@ static int lfs_deinit(lfs_t *lfs) {
#define LFSR_RCOMPAT_COMPAT \
(LFSR_RCOMPAT_GRM \
| LFSR_RCOMPAT_MMOSS \
| LFSR_RCOMPAT_MSPROUT \
| LFSR_RCOMPAT_MTREE \
| LFSR_RCOMPAT_BMOSS \
| LFSR_RCOMPAT_BSPROUT \
@@ -14148,14 +14117,6 @@ static int lfsr_mountinited(lfs_t *lfs) {
return err;
}
}
} else {
// found a direct mdir? keep track of this
if (lfsr_mtree_isnull(&lfs->mtree)) {
lfsr_mtree_frommptr(&lfs->mtree,
mdir->rbyd.blocks,
1 << lfs->mdir_bits);
}
}
// build gcksum out of mdir cksums