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t: Switched back to mid-based traversal clobbering

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Implementing gc_compact_thresh over bshrubs highlighted that it's really
not that difficult, and probably required, for traversal bshrubs to be
tracked correctly during mdir commits/compacts/splits/etc. And if we
track bshrubs across mdir commits, we might as well clobber traversals
at the mid level, allowing traversals to always reach btrees/bshrubs not
under active mutation.

One key thing to note: we should never be traversing a bshrub that is
not referenced elsewhere, either on-disk in an mdir or in-ram via an
opened file. So any compacted traversal bshrubs are not wasted prog
cycles.

This moves most of the clobbering logic back up into the high-level
functions (lfsr_remove/rename mainly), where we know which mids may be
clobbered.

This has a code cost, but it's really not all that much for more
thorough/correct filesystem traversals under mutation:

           code          stack
  before: 35268           2680
  after:  35368 (+0.3%)   2680 (+0.0%)

Unfortunately, lingering rbyd references in our btraversal structs are
still an issue, and some bshrub tests are failing... Though I do have
some ideas on how to fix this.
This commit is contained in:
Christopher Haster
2024-07-02 17:34:21 -05:00
parent 7f4384fa27
commit 7fdf0b7d23
2 changed files with 242 additions and 84 deletions
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lfs.c
+46 -44
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@@ -5945,7 +5945,7 @@ static bool lfsr_omdir_ismidopen(lfs_t *lfs, lfsr_smid_t mid) {
// needed in lfsr_omdir_clobber
static void lfsr_traversal_clobber(lfs_t *lfs, lfsr_traversal_t *t,
lfsr_smid_t mid);
lfsr_smid_t shift);
// traversal invalidation things
static void lfsr_omdir_clobber(lfs_t *lfs, lfsr_omdir_t *o, bool dirty) {
@@ -5958,7 +5958,7 @@ static void lfsr_omdir_clobber(lfs_t *lfs, lfsr_omdir_t *o, bool dirty) {
// clobber any traversals referencing our mdir
if (t->mt.o == o) {
lfsr_traversal_clobber(lfs, t, -1);
lfsr_traversal_clobber(lfs, t, +1);
}
}
}
@@ -7839,30 +7839,23 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
}
}
// clobber any related traversals
// mark all traversals as dirty
for (lfsr_omdir_t *o = lfs->omdirs; o; o = o->next) {
if (o->type == LFS_TYPE_TRAVERSAL) {
// don't clobber the current mdir, we assume upper layers know
// what they're doing
if (&o->mdir == mdir) {
continue;
}
// mark all traversals as dirty
((lfsr_traversal_t*)o)->mt.flags |= LFS_F_DIRTY;
}
}
// clobber any mdir related traversals
if (lfsr_mdir_cmp(&o->mdir, mdir) == 0) {
lfsr_traversal_clobber(lfs, (lfsr_traversal_t*)o,
lfsr_mid_bid(lfs, mdir->mid) + 1);
}
// if mroot/mtree changed, clobber any mroot/mtree traversals
if ((lfsr_mdir_cmp(&mroot_, &lfs->mroot) != 0
|| lfsr_mtree_cmp(&mtree_, &lfs->mtree) != 0)
&& o->mdir.mid == -1) {
lfsr_traversal_clobber(lfs, (lfsr_traversal_t*)o,
0);
// if mroot/mtree changed, clobber any mroot/mtree traversals
if (lfsr_mdir_cmp(&mroot_, &lfs->mroot) != 0
|| lfsr_mtree_cmp(&mtree_, &lfs->mtree) != 0) {
for (lfsr_omdir_t *o = lfs->omdirs; o; o = o->next) {
if (o->type == LFS_TYPE_TRAVERSAL
&& o->mdir.mid == -1
// don't clobber the current mdir, assume upper layers
// know what they're doing
&& &o->mdir != mdir) {
lfsr_traversal_clobber(lfs, (lfsr_traversal_t*)o, 0);
}
}
}
@@ -8419,8 +8412,9 @@ static int lfsr_mtree_traverse_(lfs_t *lfs,
// not traversing all blocks? have we exceeded our mdir's weight?
// return to mtree iteration
if (lfsr_t_ismtreeonly(mt->flags)
|| lfsr_mid_rid(lfs, mdir->mid)
>= (lfsr_srid_t)mdir->rbyd.weight) {
// mid may be -1 here if we were clobbered
|| (lfsr_rid_t)lfsr_mid_rid(lfs, mdir->mid)
>= mdir->rbyd.weight) {
mdir->mid = lfsr_mid_bid(lfs, mdir->mid) + 1;
mt->state = LFSR_MTRAVERSAL_MDIRS;
continue;
@@ -9210,6 +9204,13 @@ int lfsr_remove(lfs_t *lfs, const char *path) {
} else {
((lfsr_dir_t*)o)->pos -= 1;
}
// clobber entangled traversals
} else if (o->type == LFS_TYPE_TRAVERSAL) {
if (lfsr_f_iszombie(o->flags)) {
o->flags &= ~LFS_F_ZOMBIE;
lfsr_traversal_clobber(lfs, (lfsr_traversal_t*)o, 0);
}
}
}
@@ -9363,6 +9364,12 @@ int lfsr_rename(lfs_t *lfs, const char *old_path, const char *new_path) {
((lfsr_dir_t*)o)->pos -= 1;
}
}
// clobber entangled traversals
} else if (o->type == LFS_TYPE_TRAVERSAL
&& ((exists && o->mdir.mid == new_mdir.mid)
|| o->mdir.mid == lfs->grm.mids[0])) {
lfsr_traversal_clobber(lfs, (lfsr_traversal_t*)o, +1);
}
}
@@ -10961,7 +10968,7 @@ lfs_ssize_t lfsr_file_write(lfs_t *lfs, lfsr_file_t *file,
// checkpoint the allocator
lfs_alloc_ckpoint(lfs);
// clobber any entangled traversals
// clobber entangled traversals
lfsr_omdir_clobber(lfs, &file->o, true);
// mark as unsynced in case we fail
file->o.flags |= LFS_F_UNSYNC;
@@ -11121,7 +11128,7 @@ int lfsr_file_flush(lfs_t *lfs, lfsr_file_t *file) {
// checkpoint the allocator
lfs_alloc_ckpoint(lfs);
// clobber any entangled traversals
// clobber entangled traversals
lfsr_omdir_clobber(lfs, &file->o, true);
// flush our buffer if it contains any unwritten data
@@ -11296,6 +11303,11 @@ int lfsr_file_sync(lfs_t *lfs, lfsr_file_t *file) {
file->buffer.size);
file_->buffer.size = file->buffer.size;
}
// clobber entangled traversals
} else if (o->type == LFS_TYPE_TRAVERSAL
&& o->mdir.mid == file->o.mdir.mid) {
lfsr_traversal_clobber(lfs, (lfsr_traversal_t*)o, +1);
}
}
@@ -11384,7 +11396,7 @@ int lfsr_file_truncate(lfs_t *lfs, lfsr_file_t *file, lfs_off_t size_) {
// checkpoint the allocator
lfs_alloc_ckpoint(lfs);
// clobber any entangled traversals
// clobber entangled traversals
lfsr_omdir_clobber(lfs, &file->o, true);
// mark as unsynced in case we fail
file->o.flags |= LFS_F_UNSYNC;
@@ -11490,7 +11502,7 @@ int lfsr_file_fruncate(lfs_t *lfs, lfsr_file_t *file, lfs_off_t size_) {
// checkpoint the allocator
lfs_alloc_ckpoint(lfs);
// clobber any entangled traversals
// clobber entangled traversals
lfsr_omdir_clobber(lfs, &file->o, true);
// mark as unsynced in case we fail
file->o.flags |= LFS_F_UNSYNC;
@@ -12881,23 +12893,13 @@ done:;
}
static void lfsr_traversal_clobber(lfs_t *lfs, lfsr_traversal_t *t,
lfsr_smid_t mid) {
lfsr_smid_t shift) {
(void)lfs;
// clobber low-level traversal
if (mid != -1) {
// increment the mid (to make progress) and reset to mdir iteration
t->mt.state = LFSR_MTRAVERSAL_MDIRS;
t->o.mdir.mid = mid;
t->o.mdir.rbyd.blocks[0] = -1;
t->o.mdir.rbyd.blocks[1] = -1;
t->mt.o = NULL;
} else {
// move to next omdir
LFS_ASSERT(t->mt.state == LFSR_MTRAVERSAL_OMDIRS
|| t->mt.state == LFSR_MTRAVERSAL_OBTREE);
t->mt.state = LFSR_MTRAVERSAL_OMDIRS;
t->mt.o = t->mt.o->next;
}
// increment the mid (to make progress) and reset to mdir iteration
t->mt.state = LFSR_MTRAVERSAL_MDIR;
t->o.mdir.mid += shift;
t->mt.o = NULL;
t->mt.bshrub.u.bshrub.blocks[0] = -1;
// and clear any pending blocks
t->blocks[0] = -1;