Fixed issue where lfs_fs_deorphan may run more than needed

The underlying issue is that lfs_fs_deorphan did not updating gstate
correctly. The way it determined if there are any orphans remaining in
the filesystem was by subtracting the number of found orphans from an
internal counter.

This internal counter is a leftover from a previous implementation that
allowed leaving the lfs_fs_deorphan loop early if we know the number of
expected orphans. This can happen during recursive mdir relocations, but
with only a single bit in the gstate, can't happen during mount. If we
detect orphans during mount, we set this internal counter to 1, assuming
we will find at least one orphan.

But this presents a problem, what if we find _no_ orphans? If this happens
we never decrement the internal counter of orphans, so we would never
clear the bit in the gstate. This leads to a running lfs_fs_deorphan
on more-or-less every mutable operation in the filesystem, resulting in
an extreme performance hit.

The solution here is to not subtract the number of found orphans, but assume
that when our lfs_fs_deorphan loop finishes, we will have no orphans, because
that's the whole point of lfs_fs_deorphan.

Note that the early termination of lfs_fs_deorphan was dropped because
it would not actually change the runtime complexity of lfs_fs_deorphan,
adds code cost, and risks fragile corner cases such as this one.

---

Also added tests to assert we run lfs_fs_deorphan at most once.

Found by kasper0 and Ldd309

lfs.c

@@ -4741,8 +4741,6 @@ static int lfs_fs_deorphan(lfs_t *lfs, bool powerloss) {
         return 0;
     }
 
-    int8_t found = 0;
-
     // Check for orphans in two separate passes:
     // - 1 for half-orphans (relocations)
     // - 2 for full-orphans (removes/renames)
@@ -4813,8 +4811,6 @@ static int lfs_fs_deorphan(lfs_t *lfs, bool powerloss) {
                             return state;
                         }
 
-                        found += 1;
-
                         // did our commit create more orphans?
                         if (state == LFS_OK_ORPHANED) {
                             moreorphans = true;
@@ -4849,8 +4845,6 @@ static int lfs_fs_deorphan(lfs_t *lfs, bool powerloss) {
                         return state;
                     }
 
-                    found += 1;
-
                     // did our commit create more orphans?
                     if (state == LFS_OK_ORPHANED) {
                         moreorphans = true;
@@ -4868,9 +4862,7 @@ static int lfs_fs_deorphan(lfs_t *lfs, bool powerloss) {
     }
 
     // mark orphans as fixed
-    return lfs_fs_preporphans(lfs, -lfs_min(
+    return lfs_fs_preporphans(lfs, -lfs_gstate_getorphans(&lfs->gstate));
-            lfs_gstate_getorphans(&lfs->gstate),
-            found));
 }
 #endif
 

tests/test_orphans.toml

@@ -59,6 +59,73 @@ code = '''
     lfs_unmount(&lfs) => 0;
 '''
 
+# test that we only run deorphan once per power-cycle
+[cases.test_orphans_no_orphans]
+in = 'lfs.c'
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+
+    lfs_mount(&lfs, cfg) => 0;
+    // mark the filesystem as having orphans
+    lfs_fs_preporphans(&lfs, +1) => 0;
+    lfs_mdir_t mdir;
+    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
+    lfs_dir_commit(&lfs, &mdir, NULL, 0) => 0;
+
+    // we should have orphans at this state
+    assert(lfs_gstate_hasorphans(&lfs.gstate));
+    lfs_unmount(&lfs) => 0;
+
+    // mount
+    lfs_mount(&lfs, cfg) => 0;
+    // we should detect orphans
+    assert(lfs_gstate_hasorphans(&lfs.gstate));
+    // force consistency
+    lfs_fs_forceconsistency(&lfs) => 0;
+    // we should no longer have orphans
+    assert(!lfs_gstate_hasorphans(&lfs.gstate));
+
+    lfs_unmount(&lfs) => 0;
+'''
+
+[cases.test_orphans_one_orphan]
+in = 'lfs.c'
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+
+    lfs_mount(&lfs, cfg) => 0;
+    // create an orphan
+    lfs_mdir_t orphan;
+    lfs_alloc_ack(&lfs);
+    lfs_dir_alloc(&lfs, &orphan) => 0;
+    lfs_dir_commit(&lfs, &orphan, NULL, 0) => 0;
+
+    // append our orphan and mark the filesystem as having orphans
+    lfs_fs_preporphans(&lfs, +1) => 0;
+    lfs_mdir_t mdir;
+    lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
+    lfs_pair_tole32(orphan.pair);
+    lfs_dir_commit(&lfs, &mdir, LFS_MKATTRS(
+            {LFS_MKTAG(LFS_TYPE_SOFTTAIL, 0x3ff, 8), orphan.pair})) => 0;
+
+    // we should have orphans at this state
+    assert(lfs_gstate_hasorphans(&lfs.gstate));
+    lfs_unmount(&lfs) => 0;
+
+    // mount
+    lfs_mount(&lfs, cfg) => 0;
+    // we should detect orphans
+    assert(lfs_gstate_hasorphans(&lfs.gstate));
+    // force consistency
+    lfs_fs_forceconsistency(&lfs) => 0;
+    // we should no longer have orphans
+    assert(!lfs_gstate_hasorphans(&lfs.gstate));
+
+    lfs_unmount(&lfs) => 0;
+'''
+
 # reentrant testing for orphans, basically just spam mkdir/remove
 [cases.test_orphans_reentrant]
 reentrant = true