6.6-stable review patch. If anyone has any objections, please let me know.
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From: Julian Sun sunjunchao@bytedance.com
[ Upstream commit 46e75c56dfeafb6756773b71cabe187a6886859a ]
The following code paths may result in high latency or even task hangs: 1. fastcommit io is throttled by wbt. 2. jbd2_fc_wait_bufs() might wait for a long time while JBD2_FAST_COMMIT_ONGOING is set in journal->flags, and then jbd2_journal_commit_transaction() waits for the JBD2_FAST_COMMIT_ONGOING bit for a long time while holding the write lock of j_state_lock. 3. start_this_handle() waits for read lock of j_state_lock which results in high latency or task hang.
Given the fact that ext4_fc_commit() already modifies the current process' IO priority to match that of the jbd2 thread, it should be reasonable to match jbd2's IO submission flags as well.
Suggested-by: Ritesh Harjani (IBM) ritesh.list@gmail.com Signed-off-by: Julian Sun sunjunchao@bytedance.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Reviewed-by: Jan Kara jack@suse.cz Message-ID: 20250827121812.1477634-1-sunjunchao@bytedance.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Sasha Levin sashal@kernel.org --- fs/ext4/fast_commit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c index b527f4ab47e02..62a6960242c5a 100644 --- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -675,7 +675,7 @@ void ext4_fc_track_range(handle_t *handle, struct inode *inode, ext4_lblk_t star
static void ext4_fc_submit_bh(struct super_block *sb, bool is_tail) { - blk_opf_t write_flags = REQ_SYNC; + blk_opf_t write_flags = JBD2_JOURNAL_REQ_FLAGS; struct buffer_head *bh = EXT4_SB(sb)->s_fc_bh;
/* Add REQ_FUA | REQ_PREFLUSH only its tail */