dm: convert to idr_alloc()

Convert to the much saner new idr interface.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alasdair Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/dm.c

@@ -1755,62 +1755,38 @@ static void free_minor(int minor)
  */
 static int specific_minor(int minor)
 {
-	int r, m;
+	int r;
 
 	if (minor >= (1 << MINORBITS))
 		return -EINVAL;
 
-	r = idr_pre_get(&_minor_idr, GFP_KERNEL);
-	if (!r)
-		return -ENOMEM;
-
+	idr_preload(GFP_KERNEL);
 	spin_lock(&_minor_lock);
 
-	if (idr_find(&_minor_idr, minor)) {
-		r = -EBUSY;
-		goto out;
-	}
-
-	r = idr_get_new_above(&_minor_idr, MINOR_ALLOCED, minor, &m);
-	if (r)
-		goto out;
+	r = idr_alloc(&_minor_idr, MINOR_ALLOCED, minor, minor + 1, GFP_NOWAIT);
 
-	if (m != minor) {
-		idr_remove(&_minor_idr, m);
-		r = -EBUSY;
-		goto out;
-	}
-
-out:
 	spin_unlock(&_minor_lock);
-	return r;
+	idr_preload_end();
+	if (r < 0)
+		return r == -ENOSPC ? -EBUSY : r;
+	return 0;
 }
 
 static int next_free_minor(int *minor)
 {
-	int r, m;
-
-	r = idr_pre_get(&_minor_idr, GFP_KERNEL);
-	if (!r)
-		return -ENOMEM;
+	int r;
 
+	idr_preload(GFP_KERNEL);
 	spin_lock(&_minor_lock);
 
-	r = idr_get_new(&_minor_idr, MINOR_ALLOCED, &m);
-	if (r)
-		goto out;
-
-	if (m >= (1 << MINORBITS)) {
-		idr_remove(&_minor_idr, m);
-		r = -ENOSPC;
-		goto out;
-	}
-
-	*minor = m;
+	r = idr_alloc(&_minor_idr, MINOR_ALLOCED, 0, 1 << MINORBITS, GFP_NOWAIT);
 
-out:
 	spin_unlock(&_minor_lock);
-	return r;
+	idr_preload_end();
+	if (r < 0)
+		return r;
+	*minor = r;
+	return 0;
 }
 
 static const struct block_device_operations dm_blk_dops;