Previously, we will miss merging flush command during fsync due to below
race condition:
Thread A Thread B Thread C
- f2fs_issue_flush
- atomic_read(&issing_flush)
- f2fs_issue_flush
- atomic_read(&issing_flush)
- f2fs_issue_flush
- atomic_read(&issing_flush)
- atomic_inc(&issing_flush)
- atomic_inc(&issing_flush)
- atomic_inc(&issing_flush)
- submit_flush_wait
- submit_flush_wait
- submit_flush_wait
It needs to use atomic_inc_return instead to avoid such race.
Signed-off-by: Chao Yu <[email protected]>
---
fs/f2fs/segment.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index d6c3f456ea51..1215ca1bd4e2 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -536,8 +536,7 @@ int f2fs_issue_flush(struct f2fs_sb_info *sbi)
return ret;
}
- if (!atomic_read(&fcc->issing_flush)) {
- atomic_inc(&fcc->issing_flush);
+ if (atomic_inc_return(&fcc->issing_flush) == 1) {
ret = submit_flush_wait(sbi);
atomic_dec(&fcc->issing_flush);
@@ -547,7 +546,6 @@ int f2fs_issue_flush(struct f2fs_sb_info *sbi)
init_completion(&cmd.wait);
- atomic_inc(&fcc->issing_flush);
llist_add(&cmd.llnode, &fcc->issue_list);
/* update issue_list before we wake up issue_flush thread */
--
2.13.1.388.g69e6b9b4f4a9
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