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>

1 files changed, 41 insertions, 35 deletions

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index d066190f997a..e0061a906ba8 100644
--- 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;