Just like get_tree_bdev needs to drop s_umount when opening the main device, we need to do the same for the ext4 log device to avoid a potential lock order reversal with s_unmount for the mark_dead path. It might be preferable to just drop s_umount over ->fill_super entirely, but that will require a fairly massive audit first, so we'll do the easy version here first. Signed-off-by: Christoph Hellwig <hch@xxxxxx> --- fs/ext4/super.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 193d665813b611..2ccb19d345c6dd 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5854,7 +5854,10 @@ static journal_t *ext4_get_dev_journal(struct super_block *sb, if (WARN_ON_ONCE(!ext4_has_feature_journal(sb))) return NULL; + /* see get_tree_bdev why this is needed and safe */ + up_write(&sb->s_umount); bdev = ext4_blkdev_get(j_dev, sb); + down_write(&sb->s_umount); if (bdev == NULL) return NULL; -- 2.39.2
