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f2fs: fix to avoid migrating empty section

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It reports a bug from device w/ zufs:

F2FS-fs (dm-64): Inconsistent segment (173822) type [1, 0] in SSA and SIT
F2FS-fs (dm-64): Stopped filesystem due to reason: 4

Thread A				Thread B
- f2fs_expand_inode_data
 - f2fs_allocate_pinning_section
  - f2fs_gc_range
   - do_garbage_collect w/ segno #x
					- writepage
					 - f2fs_allocate_data_block
					  - new_curseg
					   - allocate segno #x

The root cause is: fallocate on pinning file may race w/ block allocation
as above, result in do_garbage_collect() from fallocate() may migrate
segment which is just allocated by a log, the log will update segment type
in its in-memory structure, however GC will get segment type from on-disk
SSA block, once segment type changes by log, we can detect such
inconsistency, then shutdown filesystem.

In this case, on-disk SSA shows type of segno #173822 is 1 (SUM_TYPE_NODE),
however segno #173822 was just allocated as data type segment, so in-memory
SIT shows type of segno #173822 is 0 (SUM_TYPE_DATA).

Change as below to fix this issue:
- check whether current section is empty before gc
- add sanity checks on do_garbage_collect() to avoid any race case, result
in migrating segment used by log.
- btw, it fixes misc issue in printed logs: "SSA and SIT" -> "SIT and SSA".

Fixes: 9703d69d9d ("f2fs: support file pinning for zoned devices")
Cc: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Chao Yu
2025-09-16 02:12:11 +00:00
committed by Jaegeuk Kim
parent 9251a9e6e8
commit d625a2b08c
1 changed files with 15 additions and 1 deletions
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fs/f2fs/gc.c
+15 -1
View File
@@ -1794,6 +1794,13 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
struct folio *sum_folio = filemap_get_folio(META_MAPPING(sbi),
GET_SUM_BLOCK(sbi, segno));
if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno))) {
f2fs_err(sbi, "%s: segment %u is used by log",
__func__, segno);
f2fs_bug_on(sbi, 1);
goto skip;
}
if (get_valid_blocks(sbi, segno, false) == 0)
goto freed;
if (gc_type == BG_GC && __is_large_section(sbi) &&
@@ -1805,7 +1812,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
sum = folio_address(sum_folio);
if (type != GET_SUM_TYPE((&sum->footer))) {
f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SSA and SIT",
f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SIT and SSA",
segno, type, GET_SUM_TYPE((&sum->footer)));
f2fs_stop_checkpoint(sbi, false,
STOP_CP_REASON_CORRUPTED_SUMMARY);
@@ -2068,6 +2075,13 @@ int f2fs_gc_range(struct f2fs_sb_info *sbi,
.iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
};
/*
* avoid migrating empty section, as it can be allocated by
* log in parallel.
*/
if (!get_valid_blocks(sbi, segno, true))
continue;
if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno)))
continue;