cluster/afr: if a subvolume is down wind the lock request to next

When one of the subvolume is down, then lock request is not attempted
on that subvolume and move on to the next subvolume.

/* skip over children that are down */
                while ((child_index < priv->child_count)
                       && !local->child_up[child_index])
                        child_index++;

In the above case if there are 2 subvolumes and 2nd subvolume is down (subvolume
1 from afr's view), then after attempting lock on 1st child (i.e subvolume 0)
child index is calculated to be 1. But since the 2nd child is down child_index
is incremented to 2 as per the above logic and lock request is STACK_WINDed to
the child with child_index 2. Since there are only 2 children for afr the child
(i.e the xlator_t pointer) for child_index will be NULL. The process crashes
when it dereference the NULL xlator object.

Change-Id: Icd9b5ad28bac1b805e6e80d53c12d296526bedf5
BUG: 765564
Signed-off-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-on: http://review.gluster.org/4438
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 16 insertions, 15 deletions

diff --git a/xlators/cluster/afr/src/afr-lk-common.c b/xlators/cluster/afr/src/afr-lk-common.c
index 265330d115b..542b2959d83 100644
--- a/xlators/cluster/afr/src/afr-lk-common.c
+++ b/xlators/cluster/afr/src/afr-lk-common.c
@@ -1019,6 +1019,17 @@ afr_is_entrylk (afr_internal_lock_t *int_lock,
         return is_entrylk;
 }
 
+static gf_boolean_t
+_is_lock_wind_needed (afr_local_t *local, int child_index)
+{
+        if (!local->child_up[child_index])
+                return _gf_false;
+        else if (local->fd && !local->fd_open_on[child_index])
+                return _gf_false;
+
+        return _gf_true;
+}
+
 int
 afr_lock_blocking (call_frame_t *frame, xlator_t *this, int cookie)
 {
@@ -1059,20 +1070,6 @@ afr_lock_blocking (call_frame_t *frame, xlator_t *this, int cookie)
 
                         return 0;
                 }
-
-                /* skip over children that or down
-                   or don't have the fd open */
-
-                while ((child_index < priv->child_count)
-                       && (!local->child_up[child_index] ||
-                          !local->fd_open_on[child_index]))
-
-                        child_index++;
-        } else {
-                /* skip over children that are down */
-                while ((child_index < priv->child_count)
-                       && !local->child_up[child_index])
-                        child_index++;
         }
 
         if (int_lock->lk_expected_count == int_lock->lk_attempted_count) {
@@ -1107,6 +1104,11 @@ afr_lock_blocking (call_frame_t *frame, xlator_t *this, int cookie)
                 return 0;
         }
 
+        if (!_is_lock_wind_needed (local, child_index)) {
+                afr_lock_blocking (frame, this, cookie + 1);
+                return 0;
+        }
+
         switch (local->transaction.type) {
         case AFR_DATA_TRANSACTION:
         case AFR_METADATA_TRANSACTION:
@@ -1144,7 +1146,6 @@ afr_lock_blocking (call_frame_t *frame, xlator_t *this, int cookie)
         case AFR_ENTRY_TRANSACTION:
                 /*Accounting for child_index increments on 'down'
                  *and 'fd-less' children */
-                cookie = lockee_no * priv->child_count + child_index;
 
                 if (local->fd) {
                         AFR_TRACE_ENTRYLK_IN (frame, this, AFR_ENTRYLK_TRANSACTION,