[f2fs-dev] [PATCH AUTOSEL 5.15 1/7] f2fs: quota: fix potential deadlock

[f2fs-dev] [PATCH AUTOSEL 5.15 1/7] f2fs: quota: fix potential deadlock

[Sasha Levin]

From: Chao Yu <chao@kernel.org>

[ Upstream commit a5c0042200b28fff3bde6fa128ddeaef97990f8d ]

As Yi Zhuang reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=214299

There is potential deadlock during quota data flush as below:

Thread A:			Thread B:
f2fs_dquot_acquire
down_read(&sbi->quota_sem)
				f2fs_write_checkpoint
				block_operations
				f2fs_look_all
				down_write(&sbi->cp_rwsem)
f2fs_quota_write
f2fs_write_begin
__do_map_lock
f2fs_lock_op
down_read(&sbi->cp_rwsem)
				__need_flush_qutoa
				down_write(&sbi->quota_sem)

This patch changes block_operations() to use trylock, if it fails,
it means there is potential quota data updater, in this condition,
let's flush quota data first and then trylock again to check dirty
status of quota data.

The side effect is: in heavy race condition (e.g. multi quota data
upaters vs quota data flusher), it may decrease the probability of
synchronizing quota data successfully in checkpoint() due to limited
retry time of quota flush.

Reported-by: Yi Zhuang <zhuangyi1@huawei.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/f2fs/checkpoint.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 83e9bc0f91ffd..7b02827242312 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1162,7 +1162,8 @@ static bool __need_flush_quota(struct f2fs_sb_info *sbi)
 	if (!is_journalled_quota(sbi))
 		return false;
 
-	down_write(&sbi->quota_sem);
+	if (!down_write_trylock(&sbi->quota_sem))
+		return true;
 	if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH)) {
 		ret = false;
 	} else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR)) {
-- 
2.33.0



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[f2fs-dev] [PATCH AUTOSEL 5.15 2/7] f2fs: set SBI_NEED_FSCK flag when inconsistent node block found

[Sasha Levin]

From: Weichao Guo <guoweichao@oppo.com>

[ Upstream commit 6663b138ded1a59e630c9e605e42aa7fde490cdc ]

Inconsistent node block will cause a file fail to open or read,
which could make the user process crashes or stucks. Let's mark
SBI_NEED_FSCK flag to trigger a fix at next fsck time. After
unlinking the corrupted file, the user process could regenerate
a new one and work correctly.

Signed-off-by: Weichao Guo <guoweichao@oppo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/f2fs/node.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index e863136081b47..556fcd8457f3f 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1443,6 +1443,7 @@ static struct page *__get_node_page(struct f2fs_sb_info *sbi, pgoff_t nid,
 			  nid, nid_of_node(page), ino_of_node(page),
 			  ofs_of_node(page), cpver_of_node(page),
 			  next_blkaddr_of_node(page));
+		set_sbi_flag(sbi, SBI_NEED_FSCK);
 		err = -EINVAL;
 out_err:
 		ClearPageUptodate(page);
-- 
2.33.0



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