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>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index d9a0e2205762f84da1ba16f63985179db77d5ed2..fc0cdd1612b1d6b04b5b4b0e26be78e03546ff45 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1110,7 +1110,7 @@ out_putf:
        return error;
 }
 
-static void __loop_clr_fd(struct loop_device *lo)
+static void __loop_clr_fd(struct loop_device *lo, bool release)
 {
        struct file *filp;
        gfp_t gfp = lo->old_gfp_mask;
@@ -1139,8 +1139,13 @@ static void __loop_clr_fd(struct loop_device *lo)
        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);
@@ -1163,7 +1168,8 @@ static void __loop_clr_fd(struct loop_device *lo)
        /* let user-space know about this change */
        kobject_uevent(&disk_to_dev(lo->lo_disk)->kobj, KOBJ_CHANGE);
        mapping_set_gfp_mask(filp->f_mapping, gfp);
-       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);
 
@@ -1201,7 +1207,7 @@ static void loop_rundown_workfn(struct work_struct *work)
        struct block_device *bdev = lo->lo_device;
        struct gendisk *disk = lo->lo_disk;
 
-       __loop_clr_fd(lo);
+       __loop_clr_fd(lo, true);
        kobject_put(&bdev->bd_device.kobj);
        module_put(disk->fops->owner);
        loop_rundown_completed(lo);
@@ -1247,7 +1253,7 @@ static int loop_clr_fd(struct loop_device *lo)
        lo->lo_state = Lo_rundown;
        mutex_unlock(&lo->lo_mutex);
 
-       __loop_clr_fd(lo);
+       __loop_clr_fd(lo, false);
        loop_rundown_completed(lo);
        return 0;
 }