md: sync blockdev before stopping raid or setting readonly

Commit a05b7ea ("md: avoid crash when stopping md array races
with closing other open fds.") added sync_block before stopping raid and
setting readonly. Later in commit 260fa03 ("md: avoid deadlock when
dirty buffers during md_stop.") it is moved to ioctl. array_state_store()
was ignored. Add sync blockdev to array_state_store() now.

Signed-off-by: Li Nan <[email protected]>
Signed-off-by: Song Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Li Nan

drivers/md/md.c

@@ -4500,6 +4500,17 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
 	case broken:		/* cannot be set */
 	case bad_word:
 		return -EINVAL;
+	case clear:
+	case readonly:
+	case inactive:
+	case read_auto:
+		if (!mddev->pers || !md_is_rdwr(mddev))
+			break;
+		/* write sysfs will not open mddev and opener should be 0 */
+		err = mddev_set_closing_and_sync_blockdev(mddev, 0);
+		if (err)
+			return err;
+		break;
 	default:
 		break;
 	}
@@ -4599,6 +4610,11 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
 		sysfs_notify_dirent_safe(mddev->sysfs_state);
 	}
 	mddev_unlock(mddev);
+
+	if (st == readonly || st == read_auto || st == inactive ||
+	    (err && st == clear))
+		clear_bit(MD_CLOSING, &mddev->flags);
+
 	return err ?: len;
 }
 static struct md_sysfs_entry md_array_state =