cluster/ec: Mark release only when it is acquired

Problem:
Mount-1                                Mount-2
1)Tries to acquire lock on 'dir1'   1)Tries to acquire lock on 'dir1'
2)Lock is granted on brick-0        2)Lock gets EAGAIN on brick-0 and
				      leads to blocking lock on brick-0
3)Gets a lock-contention            3) Doesn't matter what happens on mount-2
  notification, marks lock->release    from here on.
  to true.
4)New fop comes on 'dir1' which will
  be put in frozen list as lock->release
  is set to true.
5) Lock acquisition from step-2 fails because
3 bricks went down in 4+2 setup.

Fop on mount-1 which is put in frozen list will hang because no codepath will
move it from frozen list to any other list and the lock will not be retried.

Fix:
Don't set lock->release to true if lock is not acquired at the time of
lock-contention-notification

fixes: bz#1743573
Change-Id: Ie6630db8735ccf372cc54b873a3a3aed7a6082b7
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>

2 files changed, 19 insertions, 2 deletions

diff --git a/xlators/cluster/ec/src/ec-common.c b/xlators/cluster/ec/src/ec-common.c
index dea987ef319..9045a336c56 100644
--- a/xlators/cluster/ec/src/ec-common.c
+++ b/xlators/cluster/ec/src/ec-common.c
@@ -1867,6 +1867,10 @@ ec_lock_acquired(ec_lock_link_t *link)
     LOCK(&lock->loc.inode->lock);
 
     lock->acquired = _gf_true;
+    if (lock->contention) {
+        lock->release = _gf_true;
+        lock->contention = _gf_false;
+    }
 
     ec_lock_update_fd(lock, fop);
     ec_lock_wake_shared(lock, &list);
@@ -1892,15 +1896,20 @@ ec_locked(call_frame_t *frame, void *cookie, xlator_t *this, int32_t op_ret,
     ec_lock_link_t *link = NULL;
     ec_lock_t *lock = NULL;
 
+    link = fop->data;
+    lock = link->lock;
     if (op_ret >= 0) {
-        link = fop->data;
-        lock = link->lock;
         lock->mask = lock->good_mask = fop->good;
         lock->healing = 0;
 
         ec_lock_acquired(link);
         ec_lock(fop->parent);
     } else {
+        LOCK(&lock->loc.inode->lock);
+        {
+            lock->contention = _gf_false;
+        }
+        UNLOCK(&lock->loc.inode->lock);
         gf_msg(this->name, GF_LOG_WARNING, op_errno, EC_MSG_PREOP_LOCK_FAILED,
                "Failed to complete preop lock");
     }
@@ -2547,6 +2556,13 @@ ec_lock_release(ec_t *ec, inode_t *inode)
     gf_msg_debug(ec->xl->name, 0, "Releasing inode %p due to lock contention",
                  inode);
 
+    if (!lock->acquired) {
+        /* This happens if some bricks already got the lock while inodelk is in
+         * progress.  Set release to true after lock is acquired*/
+        lock->contention = _gf_true;
+        goto done;
+    }
+
     /* The lock is not marked to be released, so the frozen list should be
      * empty. */
     GF_ASSERT(list_empty(&lock->frozen));
diff --git a/xlators/cluster/ec/src/ec-types.h b/xlators/cluster/ec/src/ec-types.h
index 9c790380d4d..2568b6b3223 100644
--- a/xlators/cluster/ec/src/ec-types.h
+++ b/xlators/cluster/ec/src/ec-types.h
@@ -267,6 +267,7 @@ struct _ec_lock {
     uint32_t refs_pending;  /* Refs assigned to fops being prepared */
     uint32_t waiting_flags; /*Track xattrop/dirty marking*/
     gf_boolean_t acquired;
+    gf_boolean_t contention;
     gf_boolean_t unlock_now;
     gf_boolean_t release;
     gf_boolean_t query;