2 files changed, 20 insertions, 8 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5b98bea4ff9b..5614500092e3 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -359,6 +359,7 @@ static mddev_t * mddev_find(dev_t unit)
         else
                 new->md_minor = MINOR(unit) >> MdpMinorShift;
 
+        mutex_init(&new->open_mutex);
         mutex_init(&new->reconfig_mutex);
         INIT_LIST_HEAD(&new->disks);
         INIT_LIST_HEAD(&new->all_mddevs);
@@ -4304,12 +4305,11 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
         struct gendisk *disk = mddev->gendisk;
         mdk_rdev_t *rdev;
 
+        mutex_lock(&mddev->open_mutex);
         if (atomic_read(&mddev->openers) > is_open) {
                 printk("md: %s still in use.\n",mdname(mddev));
-                return -EBUSY;
-        }
-
-        if (mddev->pers) {
+                err = -EBUSY;
+        } else if (mddev->pers) {
 
                 if (mddev->sync_thread) {
                         set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
@@ -4367,7 +4367,10 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
                         set_disk_ro(disk, 1);
                 clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
         }
-
+out:
+        mutex_unlock(&mddev->open_mutex);
+        if (err)
+                return err;
         /*
          * Free resources if final stop
          */
@@ -4433,7 +4436,6 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
         blk_integrity_unregister(disk);
         md_new_event(mddev);
         sysfs_notify_dirent(mddev->sysfs_state);
-out:
         return err;
 }
 
@@ -5518,12 +5520,12 @@ static int md_open(struct block_device *bdev, fmode_t mode)
         }
         BUG_ON(mddev != bdev->bd_disk->private_data);
 
-        if ((err = mutex_lock_interruptible_nested(&mddev->reconfig_mutex, 1)))
+        if ((err = mutex_lock_interruptible(&mddev->open_mutex)))
                 goto out;
 
         err = 0;
         atomic_inc(&mddev->openers);
-        mddev_unlock(mddev);
+        mutex_unlock(&mddev->open_mutex);
 
         check_disk_change(bdev);
  out:
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 78f03168baf9..f8fc188bc762 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -223,6 +223,16 @@ struct mddev_s
                                                             * so we don't loop trying */
 
         int                             in_sync;        /* know to not need resync */
+        /* 'open_mutex' avoids races between 'md_open' and 'do_md_stop', so
+         * that we are never stopping an array while it is open.
+         * 'reconfig_mutex' protects all other reconfiguration.
+         * These locks are separate due to conflicting interactions
+         * with bdev->bd_mutex.
+         * Lock ordering is:
+         *  reconfig_mutex -> bd_mutex : e.g. do_md_run -> revalidate_disk
+         *  bd_mutex -> open_mutex:  e.g. __blkdev_get -> md_open
+         */
+        struct mutex                    open_mutex;
         struct mutex                    reconfig_mutex;
         atomic_t                        active;         /* general refcount */
         atomic_t                        openers;        /* number of active opens */