block: move bdev_mark_dead out of disk_check_media_change

disk_check_media_change is mostly called from ->open where it makes
little sense to mark the file system on the device as dead, as we
are just opening it. So instead of calling bdev_mark_dead from
disk_check_media_change move it into the few callers that are not
in an open instance. This avoid calling into bdev_mark_dead and
thus taking s_umount with open_mutex held.

Signed-off-by: Christoph Hellwig <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Ming Lei <[e-mail]>
Reviewed-by: Christian Brauner <[e-mail]>
Reviewed-by: Jan Kara <[e-mail]>
Reviewed-by: Jens Axboe <[e-mail]>
Signed-off-by: Christian Brauner <[e-mail]>

block/bdev.c

···
 
 	invalidate_bdev(bdev);
 }
-#ifdef CONFIG_DASD_MODULE
 /*
- * Drivers should not use this directly, but the DASD driver has historically
- * had a shutdown to offline mode that doesn't actually remove the gendisk
- * that otherwise looks a lot like a safe device removal.
+ * New drivers should not use this directly.  There are some drivers however
+ * that needs this for historical reasons. For example, the DASD driver has
+ * historically had a shutdown to offline mode that doesn't actually remove the
+ * gendisk that otherwise looks a lot like a safe device removal.
  */
 EXPORT_SYMBOL_GPL(bdev_mark_dead);
-#endif
 
 void sync_bdevs(bool wait)
 {

block/disk-events.c

···
  * disk_check_media_change - check if a removable media has been changed
  * @disk: gendisk to check
  *
- * Check whether a removable media has been changed, and attempt to free all
- * dentries and inodes and invalidates all block device page cache entries in
- * that case.
- *
- * Returns %true if the media has changed, or %false if not.
+ * Returns %true and marks the disk for a partition rescan whether a removable
+ * media has been changed, and %false if the media did not change.
  */
 bool disk_check_media_change(struct gendisk *disk)
 {
···
 
 	events = disk_clear_events(disk, DISK_EVENT_MEDIA_CHANGE |
 				   DISK_EVENT_EJECT_REQUEST);
-	if (!(events & DISK_EVENT_MEDIA_CHANGE))
-		return false;
-
-	bdev_mark_dead(disk->part0, true);
-	set_bit(GD_NEED_PART_SCAN, &disk->state);
-	return true;
+	if (events & DISK_EVENT_MEDIA_CHANGE) {
+		set_bit(GD_NEED_PART_SCAN, &disk->state);
+		return true;
+	}
+	return false;
 }
 EXPORT_SYMBOL(disk_check_media_change);
 

drivers/block/ataflop.c

···
 		/* invalidate the buffer track to force a reread */
 		BufferDrive = -1;
 		set_bit(drive, &fake_change);
-		if (disk_check_media_change(disk))
+		if (disk_check_media_change(disk)) {
+			bdev_mark_dead(disk->part0, true);
 			floppy_revalidate(disk);
+		}
 		return 0;
 	default:
 		return -EINVAL;

drivers/block/floppy.c

···
 	/* invalidate the buffer track to force a reread */
 	set_bit((long)disk->private_data, &fake_change);
 	process_fd_request();
-	if (disk_check_media_change(disk))
+	if (disk_check_media_change(disk)) {
+		bdev_mark_dead(disk->part0, true);
 		floppy_revalidate(disk);
+	}
 	return 0;
 }