md: Don't clear MD_CLOSING when the raid is about to stop

The raid should not be opened anymore when it is about to be stopped.
However, other processes can open it again if the flag MD_CLOSING is
cleared before exiting. From now on, this flag will not be cleared when
the raid will be stopped.

Fixes: 065e519 ("md: MD_CLOSING needs to be cleared after called md_set_readonly or do_md_stop")
Signed-off-by: Li Nan <[email protected]>
Reviewed-by: Yu Kuai <[email protected]>
Signed-off-by: Song Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Li Nan

drivers/md/md.c

@@ -6265,7 +6265,15 @@ static void md_clean(struct mddev *mddev)
 	mddev->persistent = 0;
 	mddev->level = LEVEL_NONE;
 	mddev->clevel[0] = 0;
-	mddev->flags = 0;
+	/*
+	 * Don't clear MD_CLOSING, or mddev can be opened again.
+	 * 'hold_active != 0' means mddev is still in the creation
+	 * process and will be used later.
+	 */
+	if (mddev->hold_active)
+		mddev->flags = 0;
+	else
+		mddev->flags &= BIT_ULL_MASK(MD_CLOSING);
 	mddev->sb_flags = 0;
 	mddev->ro = MD_RDWR;
 	mddev->metadata_type[0] = 0;
@@ -7603,7 +7611,6 @@ static int md_ioctl(struct block_device *bdev, blk_mode_t mode,
 	int err = 0;
 	void __user *argp = (void __user *)arg;
 	struct mddev *mddev = NULL;
-	bool did_set_md_closing = false;
 
 	err = md_ioctl_valid(cmd);
 	if (err)
@@ -7660,7 +7667,6 @@ static int md_ioctl(struct block_device *bdev, blk_mode_t mode,
 			mutex_unlock(&mddev->open_mutex);
 			return -EBUSY;
 		}
-		did_set_md_closing = true;
 		mutex_unlock(&mddev->open_mutex);
 		sync_blockdev(bdev);
 	}
@@ -7802,7 +7808,7 @@ static int md_ioctl(struct block_device *bdev, blk_mode_t mode,
 				     mddev_unlock(mddev);
 
 out:
-	if(did_set_md_closing)
+	if (cmd == STOP_ARRAY_RO || (err && cmd == STOP_ARRAY))
 		clear_bit(MD_CLOSING, &mddev->flags);
 	return err;
 }