1 files changed, 31 insertions, 1 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 952c49c3b9aa..6982f86db6dc 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -64,12 +64,14 @@ union map_info *dm_get_mapinfo(struct bio *bio)
 #define DMF_SUSPENDED 1
 #define DMF_FROZEN 2
 #define DMF_FREEING 3
+#define DMF_DELETING 4
 
 struct mapped_device {
         struct rw_semaphore io_lock;
         struct semaphore suspend_lock;
         rwlock_t map_lock;
         atomic_t holders;
+        atomic_t open_count;
 
         unsigned long flags;
 
@@ -228,12 +230,14 @@ static int dm_blk_open(struct inode *inode, struct file *file)
         if (!md)
                 goto out;
 
-        if (test_bit(DMF_FREEING, &md->flags)) {
+        if (test_bit(DMF_FREEING, &md->flags) ||
+            test_bit(DMF_DELETING, &md->flags)) {
                 md = NULL;
                 goto out;
         }
 
         dm_get(md);
+        atomic_inc(&md->open_count);
 
 out:
         spin_unlock(&_minor_lock);
@@ -246,10 +250,35 @@ static int dm_blk_close(struct inode *inode, struct file *file)
         struct mapped_device *md;
 
         md = inode->i_bdev->bd_disk->private_data;
+        atomic_dec(&md->open_count);
         dm_put(md);
         return 0;
 }
 
+int dm_open_count(struct mapped_device *md)
+{
+        return atomic_read(&md->open_count);
+}
+
+/*
+ * Guarantees nothing is using the device before it's deleted.
+ */
+int dm_lock_for_deletion(struct mapped_device *md)
+{
+        int r = 0;
+
+        spin_lock(&_minor_lock);
+
+        if (dm_open_count(md))
+                r = -EBUSY;
+        else
+                set_bit(DMF_DELETING, &md->flags);
+
+        spin_unlock(&_minor_lock);
+
+        return r;
+}
+
 static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
 {
         struct mapped_device *md = bdev->bd_disk->private_data;
@@ -867,6 +896,7 @@ static struct mapped_device *alloc_dev(int minor)
         init_MUTEX(&md->suspend_lock);
         rwlock_init(&md->map_lock);
         atomic_set(&md->holders, 1);
+        atomic_set(&md->open_count, 0);
         atomic_set(&md->event_nr, 0);
 
         md->queue = blk_alloc_queue(GFP_KERNEL);