1 files changed, 27 insertions, 3 deletions

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 5e0b333793d5..834bf0f86222 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -906,6 +906,27 @@ static void close_sync(conf_t *conf)
         conf->r10buf_pool = NULL;
 }
 
+/* check if there are enough drives for
+ * every block to appear on atleast one
+ */
+static int enough(conf_t *conf)
+{
+        int first = 0;
+
+        do {
+                int n = conf->copies;
+                int cnt = 0;
+                while (n--) {
+                        if (conf->mirrors[first].rdev)
+                                cnt++;
+                        first = (first+1) % conf->raid_disks;
+                }
+                if (cnt == 0)
+                        return 0;
+        } while (first != 0);
+        return 1;
+}
+
 static int raid10_spare_active(mddev_t *mddev)
 {
         int i;
@@ -944,6 +965,8 @@ static int raid10_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
                  * very different from resync
                  */
                 return 0;
+        if (!enough(conf))
+                return 0;
 
         for (mirror=0; mirror < mddev->raid_disks; mirror++)
                 if ( !(p=conf->mirrors+mirror)->rdev) {
@@ -1684,9 +1707,10 @@ static int run(mddev_t *mddev)
         init_waitqueue_head(&conf->wait_idle);
         init_waitqueue_head(&conf->wait_resume);
 
-        if (!conf->working_disks) {
-                printk(KERN_ERR "raid10: no operational mirrors for %s\n",
-                        mdname(mddev));
+        /* need to check that every block has at least one working mirror */
+        if (!enough(conf)) {
+                printk(KERN_ERR "raid10: not enough operational mirrors for %s\n",
+                       mdname(mddev));
                 goto out_free_conf;
         }