If vfs_flush() is called with queue frozen, the queue freeze lock may be connected with FS internal lock, and lockdep warning can be triggered because the queue freeze lock is connected with too many global or sub-system locks. Fix the warning by moving vfs_fsync() out of loop_update_dio(): - vfs_fsync() is only needed when switching to dio - only loop_change_fd() and loop_configure() may switch from buffered IO to direct IO, so call vfs_fsync() directly here. This way is safe because either loop is in unbound, or new file isn't attached - for the other two cases of set_status and set_block_size, direct IO can only become off, so no need to call vfs_fsync() Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Reported-by: Kun Hu <huk23@xxxxxxxxxxxxxx> Reported-by: Jiaji Qin <jjtan24@xxxxxxxxxxxxxx> Closes: https://lore.kernel.org/linux-block/359BC288-B0B1-4815-9F01-3A349B12E816@xxxxxxxxxxxxxx/T/#u Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- drivers/block/loop.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 1ec7417c7f00..be7e20064427 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -205,8 +205,6 @@ static bool lo_can_use_dio(struct loop_device *lo) */ static inline void loop_update_dio(struct loop_device *lo) { - bool dio_in_use = lo->lo_flags & LO_FLAGS_DIRECT_IO; - lockdep_assert_held(&lo->lo_mutex); WARN_ON_ONCE(lo->lo_state == Lo_bound && lo->lo_queue->mq_freeze_depth == 0); @@ -215,10 +213,6 @@ static inline void loop_update_dio(struct loop_device *lo) lo->lo_flags |= LO_FLAGS_DIRECT_IO; if ((lo->lo_flags & LO_FLAGS_DIRECT_IO) && !lo_can_use_dio(lo)) lo->lo_flags &= ~LO_FLAGS_DIRECT_IO; - - /* flush dirty pages before starting to issue direct I/O */ - if ((lo->lo_flags & LO_FLAGS_DIRECT_IO) && !dio_in_use) - vfs_fsync(lo->lo_backing_file, 0); } /** @@ -621,6 +615,9 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev, if (get_loop_size(lo, file) != get_loop_size(lo, old_file)) goto out_err; + /* may work in dio, so flush page cache for avoiding race */ + vfs_fsync(file, 0); + /* and ... switch */ disk_force_media_change(lo->lo_disk); blk_mq_freeze_queue(lo->lo_queue); @@ -1098,6 +1095,9 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode, if (error) goto out_unlock; + /* may work in dio, so flush page cache for avoiding race */ + vfs_fsync(file, 0); + loop_update_dio(lo); loop_sysfs_init(lo); -- 2.44.0
