drbd: implicitly create unconfigured devices on sync-after dependencies

If pacemaker (for example) decided to initialize minor devices not in
the exact sync-after dependency order, the configuration partially
failed with an error "The sync-after minor number is invalid". (Bugz. #322)

We can avoid that by implicitly creating unconfigured minor devices,
if others depend on them.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index d066190..e0061a9 100644 (file)
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -413,6 +413,39 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
        return r;
 }
 
+static struct drbd_conf *ensure_mdev(int minor, int create)
+{
+       struct drbd_conf *mdev;
+
+       if (minor >= minor_count)
+               return NULL;
+
+       mdev = minor_to_mdev(minor);
+
+       if (!mdev && create) {
+               struct gendisk *disk = NULL;
+               mdev = drbd_new_device(minor);
+
+               spin_lock_irq(&drbd_pp_lock);
+               if (minor_table[minor] == NULL) {
+                       minor_table[minor] = mdev;
+                       disk = mdev->vdisk;
+                       mdev = NULL;
+               } /* else: we lost the race */
+               spin_unlock_irq(&drbd_pp_lock);
+
+               if (disk) /* we won the race above */
+                       /* in case we ever add a drbd_delete_device(),
+                        * don't forget the del_gendisk! */
+                       add_disk(disk);
+               else /* we lost the race above */
+                       drbd_free_mdev(mdev);
+
+               mdev = minor_to_mdev(minor);
+       }
+
+       return mdev;
+}
 
 static int drbd_nl_primary(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
                           struct drbd_nl_cfg_reply *reply)
@@ -1713,6 +1746,12 @@ static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *n
        }
 #undef AL_MAX
 
+       /* to avoid spurious errors when configuring minors before configuring
+        * the minors they depend on: if necessary, first create the minor we
+        * depend on */
+       if (sc.after >= 0)
+               ensure_mdev(sc.after, 1);
+
        /* most sanity checks done, try to assign the new sync-after
         * dependency.  need to hold the global lock in there,
         * to avoid a race in the dependency loop check. */
@@ -2080,40 +2119,6 @@ out:
        return 0;
 }
 
-static struct drbd_conf *ensure_mdev(struct drbd_nl_cfg_req *nlp)
-{
-       struct drbd_conf *mdev;
-
-       if (nlp->drbd_minor >= minor_count)
-               return NULL;
-
-       mdev = minor_to_mdev(nlp->drbd_minor);
-
-       if (!mdev && (nlp->flags & DRBD_NL_CREATE_DEVICE)) {
-               struct gendisk *disk = NULL;
-               mdev = drbd_new_device(nlp->drbd_minor);
-
-               spin_lock_irq(&drbd_pp_lock);
-               if (minor_table[nlp->drbd_minor] == NULL) {
-                       minor_table[nlp->drbd_minor] = mdev;
-                       disk = mdev->vdisk;
-                       mdev = NULL;
-               } /* else: we lost the race */
-               spin_unlock_irq(&drbd_pp_lock);
-
-               if (disk) /* we won the race above */
-                       /* in case we ever add a drbd_delete_device(),
-                        * don't forget the del_gendisk! */
-                       add_disk(disk);
-               else /* we lost the race above */
-                       drbd_free_mdev(mdev);
-
-               mdev = minor_to_mdev(nlp->drbd_minor);
-       }
-
-       return mdev;
-}
-
 struct cn_handler_struct {
        int (*function)(struct drbd_conf *,
                         struct drbd_nl_cfg_req *,
@@ -2174,7 +2179,8 @@ static void drbd_connector_callback(struct cn_msg *req, struct netlink_skb_parms
                goto fail;
        }
 
-       mdev = ensure_mdev(nlp);
+       mdev = ensure_mdev(nlp->drbd_minor,
+                       (nlp->flags & DRBD_NL_CREATE_DEVICE));
        if (!mdev) {
                retcode = ERR_MINOR_INVALID;
                goto fail;