md: factor out a mddev_alloc_unit helper from mddev_find

Split out a self contained helper to find a free minor for the md
"unit" number.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Song Liu <song@kernel.org>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3ce5f4e0f43180ec4d823e6a24657a6a53b20b08..8ef06330fc66e4097ed0c0c676fe1ae3e842310a 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -745,6 +745,27 @@ static struct mddev *mddev_find_locked(dev_t unit)
        return NULL;
 }
 
+/* find an unused unit number */
+static dev_t mddev_alloc_unit(void)
+{
+       static int next_minor = 512;
+       int start = next_minor;
+       bool is_free = 0;
+       dev_t dev = 0;
+
+       while (!is_free) {
+               dev = MKDEV(MD_MAJOR, next_minor);
+               next_minor++;
+               if (next_minor > MINORMASK)
+                       next_minor = 0;
+               if (next_minor == start)
+                       return 0;               /* Oh dear, all in use. */
+               is_free = !mddev_find_locked(dev);
+       }
+
+       return dev;
+}
+
 static struct mddev *mddev_find(dev_t unit)
 {
        struct mddev *mddev;
@@ -787,27 +808,13 @@ static struct mddev *mddev_find_or_alloc(dev_t unit)
                        return new;
                }
        } else if (new) {
-               /* find an unused unit number */
-               static int next_minor = 512;
-               int start = next_minor;
-               int is_free = 0;
-               int dev = 0;
-               while (!is_free) {
-                       dev = MKDEV(MD_MAJOR, next_minor);
-                       next_minor++;
-                       if (next_minor > MINORMASK)
-                               next_minor = 0;
-                       if (next_minor == start) {
-                               /* Oh dear, all in use. */
-                               spin_unlock(&all_mddevs_lock);
-                               kfree(new);
-                               return NULL;
-                       }
-
-                       is_free = !mddev_find_locked(dev);
+               new->unit = mddev_alloc_unit();
+               if (!new->unit) {
+                       spin_unlock(&all_mddevs_lock);
+                       kfree(new);
+                       return NULL;
                }
-               new->unit = dev;
-               new->md_minor = MINOR(dev);
+               new->md_minor = MINOR(new->unit);
                new->hold_active = UNTIL_STOP;
                list_add(&new->all_mddevs, &all_mddevs);
                spin_unlock(&all_mddevs_lock);