loop: only freeze the queue in __loop_clr_fd when needed

->release is only called after all outstanding I/O has completed, so only
freeze the queue when clearing the backing file of a live loop device.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20220330052917.2566582-11-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index d6315b0..d1a4af5 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1139,8 +1139,13 @@ static void __loop_clr_fd(struct loop_device *lo, bool release)
        if (test_bit(QUEUE_FLAG_WC, &lo->lo_queue->queue_flags))
                blk_queue_write_cache(lo->lo_queue, false, false);
 
-       /* freeze request queue during the transition */
-       blk_mq_freeze_queue(lo->lo_queue);
+       /*
+        * Freeze the request queue when unbinding on a live file descriptor and
+        * thus an open device.  When called from ->release we are guaranteed
+        * that there is no I/O in progress already.
+        */
+       if (!release)
+               blk_mq_freeze_queue(lo->lo_queue);
 
        destroy_workqueue(lo->workqueue);
        loop_free_idle_workers(lo, true);
@@ -1165,7 +1170,8 @@ static void __loop_clr_fd(struct loop_device *lo, bool release)
        mapping_set_gfp_mask(filp->f_mapping, gfp);
        /* This is safe: open() is still holding a reference. */
        module_put(THIS_MODULE);
-       blk_mq_unfreeze_queue(lo->lo_queue);
+       if (!release)
+               blk_mq_unfreeze_queue(lo->lo_queue);
 
        disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE);