[PATCH] dm: Repair persistent minors

From: Joe Thornber <thornber@sistina.com>

Split the dm_create() function into two variants, depending on whether you
want the device to have a specific minor number.  This avoids the broken
overloading of the minor argument to the old dm_create().

drivers/md/dm-ioctl.c

@@ -560,7 +560,6 @@ static int create(struct dm_ioctl *param, struct dm_ioctl *user)
 	int r;
 	struct dm_table *t;
 	struct mapped_device *md;
-	unsigned int minor = 0;
 
 	r = check_name(param->name);
 	if (r)
@@ -577,9 +576,10 @@ static int create(struct dm_ioctl *param, struct dm_ioctl *user)
 	}
 
 	if (param->flags & DM_PERSISTENT_DEV_FLAG)
-		minor = minor(to_kdev_t(param->dev));
+		r = dm_create_with_minor(minor(to_kdev_t(param->dev)), t, &md);
+	else
+		r = dm_create(t, &md);
 
-	r = dm_create(minor, t, &md);
 	if (r) {
 		dm_table_put(t);
 		return r;

drivers/md/dm.c

@@ -569,7 +569,7 @@ static int next_free_minor(unsigned int *minor)
 /*
  * Allocate and initialise a blank device with a given minor.
  */
-static struct mapped_device *alloc_dev(unsigned int minor)
+static struct mapped_device *alloc_dev(unsigned int minor, int persistent)
 {
 	int r;
 	struct mapped_device *md = kmalloc(sizeof(*md), GFP_KERNEL);
@@ -580,7 +580,7 @@ static struct mapped_device *alloc_dev(unsigned int minor)
 	}
 
 	/* get a minor number for the dev */
-	r = (minor < 0) ? next_free_minor(&minor) : specific_minor(minor);
+	r = persistent ? specific_minor(minor) : next_free_minor(&minor);
 	if (r < 0) {
 		kfree(md);
 		return NULL;
@@ -660,13 +660,13 @@ static void __unbind(struct mapped_device *md)
 /*
  * Constructor for a new device.
  */
-int dm_create(unsigned int minor, struct dm_table *table,
-	      struct mapped_device **result)
+static int create_aux(unsigned int minor, int persistent,
+		      struct dm_table *table, struct mapped_device **result)
 {
 	int r;
 	struct mapped_device *md;
 
-	md = alloc_dev(minor);
+	md = alloc_dev(minor, persistent);
 	if (!md)
 		return -ENXIO;
 
@@ -681,6 +681,17 @@ int dm_create(unsigned int minor, struct dm_table *table,
 	return 0;
 }
 
+int dm_create(struct dm_table *table, struct mapped_device **result)
+{
+	return create_aux(0, 0, table, result);
+}
+
+int dm_create_with_minor(unsigned int minor,
+			 struct dm_table *table, struct mapped_device **result)
+{
+	return create_aux(minor, 1, table, result);
+}
+
 void dm_get(struct mapped_device *md)
 {
 	atomic_inc(&md->holders);

drivers/md/dm.h

@@ -51,8 +51,9 @@ struct mapped_device;
  * Functions for manipulating a struct mapped_device.
  * Drop the reference with dm_put when you finish with the object.
  *---------------------------------------------------------------*/
-int dm_create(unsigned int minor, struct dm_table *table,
-	      struct mapped_device **md);
+int dm_create(struct dm_table *table, struct mapped_device **md);
+int dm_create_with_minor(unsigned int minor, struct dm_table *table,
+			 struct mapped_device **md);
 
 /*
  * Reference counting for md.