1 files changed, 26 insertions, 17 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 839373451c2b..bc31bb7072a2 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1010,9 +1010,6 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	/* This is safe, since we have a reference from open(). */
 	__module_get(THIS_MODULE);
 
-	/* suppress uevents while reconfiguring the device */
-	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
-
 	/*
 	 * If we don't hold exclusive handle for the device, upgrade to it
 	 * here to avoid changing device under exclusive owner.
@@ -1067,6 +1064,9 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 		}
 	}
 
+	/* suppress uevents while reconfiguring the device */
+	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
+
 	disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE);
 	set_disk_ro(lo->lo_disk, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
 
@@ -1109,17 +1109,17 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	if (partscan)
 		clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
 
+	/* enable and uncork uevent now that we are done */
+	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0);
+
 	loop_global_unlock(lo, is_loop);
 	if (partscan)
 		loop_reread_partitions(lo);
+
 	if (!(mode & FMODE_EXCL))
 		bd_abort_claiming(bdev, loop_configure);
 
-	error = 0;
-done:
-	/* enable and uncork uevent now that we are done */
-	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0);
-	return error;
+	return 0;
 
 out_unlock:
 	loop_global_unlock(lo, is_loop);
@@ -1130,7 +1130,7 @@ out_putf:
 	fput(file);
 	/* This is safe: open() is still holding a reference. */
 	module_put(THIS_MODULE);
-	goto done;
+	return error;
 }
 
 static void __loop_clr_fd(struct loop_device *lo, bool release)
@@ -1859,35 +1859,44 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
 
 static void loop_handle_cmd(struct loop_cmd *cmd)
 {
+	struct cgroup_subsys_state *cmd_blkcg_css = cmd->blkcg_css;
+	struct cgroup_subsys_state *cmd_memcg_css = cmd->memcg_css;
 	struct request *rq = blk_mq_rq_from_pdu(cmd);
 	const bool write = op_is_write(req_op(rq));
 	struct loop_device *lo = rq->q->queuedata;
 	int ret = 0;
 	struct mem_cgroup *old_memcg = NULL;
+	const bool use_aio = cmd->use_aio;
 
 	if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY)) {
 		ret = -EIO;
 		goto failed;
 	}
 
-	if (cmd->blkcg_css)
-		kthread_associate_blkcg(cmd->blkcg_css);
-	if (cmd->memcg_css)
+	if (cmd_blkcg_css)
+		kthread_associate_blkcg(cmd_blkcg_css);
+	if (cmd_memcg_css)
 		old_memcg = set_active_memcg(
-			mem_cgroup_from_css(cmd->memcg_css));
+			mem_cgroup_from_css(cmd_memcg_css));
 
+	/*
+	 * do_req_filebacked() may call blk_mq_complete_request() synchronously
+	 * or asynchronously if using aio. Hence, do not touch 'cmd' after
+	 * do_req_filebacked() has returned unless we are sure that 'cmd' has
+	 * not yet been completed.
+	 */
 	ret = do_req_filebacked(lo, rq);
 
-	if (cmd->blkcg_css)
+	if (cmd_blkcg_css)
 		kthread_associate_blkcg(NULL);
 
-	if (cmd->memcg_css) {
+	if (cmd_memcg_css) {
 		set_active_memcg(old_memcg);
-		css_put(cmd->memcg_css);
+		css_put(cmd_memcg_css);
 	}
  failed:
 	/* complete non-aio request */
-	if (!cmd->use_aio || ret) {
+	if (!use_aio || ret) {
 		if (ret == -EOPNOTSUPP)
 			cmd->ret = ret;
 		else