mirror/littlefs
3
0
Fork 0
mirror of https://github.com/littlefs-project/littlefs.git synced 2025-12-01 12:20:02 +00:00
Code Issues Packages Projects Releases Wiki Activity

Fixed issue where deorphan could get stuck circling between two half-orphans

Browse Source 
This of course should never happen normally, two half-orphans requires
two parents, which is disallowed in littlefs for this reason. But it can
happen if there is an outdated half-orphan later in the metadata
linked-list. The two half-orphans can cause the deorphan step to get
stuck, constantly "fixing" the first half-orphan before it has a chance
to remove the problematic, outdated half-orphan later in the list.

The solution here is to do a full check for half-orphans before
restarting the half-orphan loop. This strategy has the potential to
visit more metadata blocks unnecessarily, but avoids situations where
removing a later half-orphan will eventually cause an earlier
half-orphan to resolve itself.

Found with heuristic powerloss testing with test_relocations_reentrant_renames
after 192 nested powerlosses.
This commit is contained in:
Christopher Haster
2022-12-10 22:38:20 -06:00
parent d1b254da2c
commit ba1c76435a
1 changed files with 7 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
lfs.c
View File

@ -4603,7 +4603,6 @@ static int lfs_fs_deorphan(lfs_t *lfs, bool powerloss) {
int8_t found = 0; int8_t found = 0;
restart:
// Check for orphans in two separate passes: // Check for orphans in two separate passes:
// - 1 for half-orphans (relocations) // - 1 for half-orphans (relocations)
// - 2 for full-orphans (removes/renames) // - 2 for full-orphans (removes/renames)
@ -4612,10 +4611,12 @@ restart:
// references to full-orphans, effectively hiding them from the deorphan // references to full-orphans, effectively hiding them from the deorphan
// search. // search.
// //
for (int pass = 0; pass < 2; pass++) { int pass = 0;
while (pass < 2) {
// Fix any orphans // Fix any orphans
lfs_mdir_t pdir = {.split = true, .tail = {0, 1}}; lfs_mdir_t pdir = {.split = true, .tail = {0, 1}};
lfs_mdir_t dir; lfs_mdir_t dir;
bool moreorphans = false;
// iterate over all directory directory entries // iterate over all directory directory entries
while (!lfs_pair_isnull(pdir.tail)) { while (!lfs_pair_isnull(pdir.tail)) {
@ -4676,7 +4677,7 @@ restart:
// did our commit create more orphans? // did our commit create more orphans?
if (state == LFS_OK_ORPHANED) { if (state == LFS_OK_ORPHANED) {
goto restart; moreorphans = true;
} }
// refetch tail // refetch tail
@ -4712,7 +4713,7 @@ restart:
// did our commit create more orphans? // did our commit create more orphans?
if (state == LFS_OK_ORPHANED) { if (state == LFS_OK_ORPHANED) {
goto restart; moreorphans = true;
} }
// refetch tail // refetch tail
@ -4722,6 +4723,8 @@ restart:
pdir = dir; pdir = dir;
} }
pass = moreorphans ? 0 : pass+1;
} }
// mark orphans as fixed // mark orphans as fixed