Merge branch 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md into for-5.13/drivers

Pull MD updates from Song:

"These patches fix a race condition with md_release() and md_open()."

* 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md: split mddev_find
  md: factor out a mddev_find_locked helper from mddev_find
  md: md_open returns -EBUSY when entering racing area

1 files changed, 39 insertions, 20 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 368cad6cd53a..3ce5f4e0f431 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -734,8 +734,35 @@ void mddev_init(struct mddev *mddev)
 }
 EXPORT_SYMBOL_GPL(mddev_init);
 
+static struct mddev *mddev_find_locked(dev_t unit)
+{
+	struct mddev *mddev;
+
+	list_for_each_entry(mddev, &all_mddevs, all_mddevs)
+		if (mddev->unit == unit)
+			return mddev;
+
+	return NULL;
+}
+
 static struct mddev *mddev_find(dev_t unit)
 {
+	struct mddev *mddev;
+
+	if (MAJOR(unit) != MD_MAJOR)
+		unit &= ~((1 << MdpMinorShift) - 1);
+
+	spin_lock(&all_mddevs_lock);
+	mddev = mddev_find_locked(unit);
+	if (mddev)
+		mddev_get(mddev);
+	spin_unlock(&all_mddevs_lock);
+
+	return mddev;
+}
+
+static struct mddev *mddev_find_or_alloc(dev_t unit)
+{
 	struct mddev *mddev, *new = NULL;
 
 	if (unit && MAJOR(unit) != MD_MAJOR)
@@ -745,13 +772,13 @@ static struct mddev *mddev_find(dev_t unit)
 	spin_lock(&all_mddevs_lock);
 
 	if (unit) {
-		list_for_each_entry(mddev, &all_mddevs, all_mddevs)
-			if (mddev->unit == unit) {
-				mddev_get(mddev);
-				spin_unlock(&all_mddevs_lock);
-				kfree(new);
-				return mddev;
-			}
+		mddev = mddev_find_locked(unit);
+		if (mddev) {
+			mddev_get(mddev);
+			spin_unlock(&all_mddevs_lock);
+			kfree(new);
+			return mddev;
+		}
 
 		if (new) {
 			list_add(&new->all_mddevs, &all_mddevs);
@@ -777,12 +804,7 @@ static struct mddev *mddev_find(dev_t unit)
 				return NULL;
 			}
 
-			is_free = 1;
-			list_for_each_entry(mddev, &all_mddevs, all_mddevs)
-				if (mddev->unit == dev) {
-					is_free = 0;
-					break;
-				}
+			is_free = !mddev_find_locked(dev);
 		}
 		new->unit = dev;
 		new->md_minor = MINOR(dev);
@@ -5644,7 +5666,7 @@ static int md_alloc(dev_t dev, char *name)
 	 * writing to /sys/module/md_mod/parameters/new_array.
 	 */
 	static DEFINE_MUTEX(disks_mutex);
-	struct mddev *mddev = mddev_find(dev);
+	struct mddev *mddev = mddev_find_or_alloc(dev);
 	struct gendisk *disk;
 	int partitioned;
 	int shift;
@@ -6524,11 +6546,9 @@ static void autorun_devices(int part)
 
 		md_probe(dev);
 		mddev = mddev_find(dev);
-		if (!mddev || !mddev->gendisk) {
-			if (mddev)
-				mddev_put(mddev);
+		if (!mddev)
 			break;
-		}
+
 		if (mddev_lock(mddev))
 			pr_warn("md: %s locked, cannot run\n", mdname(mddev));
 		else if (mddev->raid_disks || mddev->major_version
@@ -7821,8 +7841,7 @@ static int md_open(struct block_device *bdev, fmode_t mode)
 		/* Wait until bdev->bd_disk is definitely gone */
 		if (work_pending(&mddev->del_work))
 			flush_workqueue(md_misc_wq);
-		/* Then retry the open from the top */
-		return -ERESTARTSYS;
+		return -EBUSY;
 	}
 	BUG_ON(mddev != bdev->bd_disk->private_data);