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* [PATCH v5] f2fs: prevent the current section from being selected as a victim during GC
@ 2025-04-03 23:21 yohan.joung
  2025-04-04 19:55 ` Jaegeuk Kim
  0 siblings, 1 reply; 8+ messages in thread
From: yohan.joung @ 2025-04-03 23:21 UTC (permalink / raw)
  To: jaegeuk, chao; +Cc: linux-f2fs-devel, linux-kernel, pilhyun.kim, yohan.joung

When selecting a victim using next_victim_seg in a large section, the
selected section might already have been cleared and designated as the
new current section, making it actively in use.
This behavior causes inconsistency between the SIT and SSA.

F2FS-fs (dm-54): Inconsistent segment (70961) type [0, 1] in SSA and SIT
Call trace:
dump_backtrace+0xe8/0x10c
show_stack+0x18/0x28
dump_stack_lvl+0x50/0x6c
dump_stack+0x18/0x28
f2fs_stop_checkpoint+0x1c/0x3c
do_garbage_collect+0x41c/0x271c
f2fs_gc+0x27c/0x828
gc_thread_func+0x290/0x88c
kthread+0x11c/0x164
ret_from_fork+0x10/0x20

issue scenario
segs_per_sec=2
- seg#0 and seg#1 are all dirty
- all valid blocks are removed in seg#1
- gc select this sec and next_victim_seg=seg#0
- migrate seg#0, next_victim_seg=seg#1
- checkpoint -> sec(seg#0, seg#1)  becomes free
- allocator assigns sec(seg#0, seg#1) to curseg
- gc tries to migrate seg#1

Signed-off-by: yohan.joung <yohan.joung@sk.com>
Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/segment.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index 0465dc00b349..0773283babfa 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -474,8 +474,15 @@ static inline void __set_test_and_free(struct f2fs_sb_info *sbi,
 		next = find_next_bit(free_i->free_segmap,
 				start_segno + SEGS_PER_SEC(sbi), start_segno);
 		if (next >= start_segno + usable_segs) {
-			if (test_and_clear_bit(secno, free_i->free_secmap))
+			if (test_and_clear_bit(secno, free_i->free_secmap)) {
 				free_i->free_sections++;
+
+				if (GET_SEC_FROM_SEG(sbi, sbi->next_victim_seg[BG_GC]) == secno)
+					sbi->next_victim_seg[BG_GC] = NULL_SEGNO;
+
+				if (GET_SEC_FROM_SEG(sbi, sbi->next_victim_seg[FG_GC]) == secno)
+					sbi->next_victim_seg[FG_GC] = NULL_SEGNO;
+			}
 		}
 	}
 skip_free:
-- 
2.33.0


^ permalink raw reply related	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2025-04-10  5:24 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-04-03 23:21 [PATCH v5] f2fs: prevent the current section from being selected as a victim during GC yohan.joung
2025-04-04 19:55 ` Jaegeuk Kim
2025-04-07  2:08   ` Chao Yu
2025-04-07  2:11     ` Chao Yu
2025-04-10  3:53       ` Jaegeuk Kim
2025-04-10  5:12         ` [f2fs-dev] " yohan.joung
2025-04-10  5:23           ` yohan.joung
2025-04-10  5:14         ` Chao Yu

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