lockdep reports a possible deadlock due to lock order inversion: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&sbi->s_fc_lock); lock(fs_reclaim); lock(&sbi->s_fc_lock); ext4_fc_perform_commit() holds s_fc_lock while writing the fast commit log. Allocations here can enter reclaim and take fs_reclaim, inverting with ext4_fc_del() which runs under fs_reclaim during inode eviction. Wrap Step 6 in memalloc_nofs_save()/restore() so reclaim is skipped while s_fc_lock is held. Fixes: 6593714d67ba ("ext4: hold s_fc_lock while during fast commit") Signed-off-by: Li Chen --- fs/ext4/fast_commit.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c index 3bcdd4619de1..b0c458082997 100644 --- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -1045,6 +1045,7 @@ static int ext4_fc_perform_commit(journal_t *journal) struct ext4_fc_head head; struct inode *inode; struct blk_plug plug; + unsigned int nofs; int ret = 0; u32 crc = 0; @@ -1118,6 +1119,7 @@ static int ext4_fc_perform_commit(journal_t *journal) blkdev_issue_flush(journal->j_fs_dev); blk_start_plug(&plug); + nofs = memalloc_nofs_save(); /* Step 6: Write fast commit blocks to disk. */ if (sbi->s_fc_bytes == 0) { /* @@ -1158,6 +1160,7 @@ static int ext4_fc_perform_commit(journal_t *journal) out: mutex_unlock(&sbi->s_fc_lock); + memalloc_nofs_restore(nofs); blk_finish_plug(&plug); return ret; } -- 2.52.0