features/quota: maintain correct link_count in ancestry building

codepath.

Ancestry building codepath can be executed simultaneously when a file
has hardlinks. So, following fixes are needed:

* modify local->link_count under locks in ancestry building codepath.
* before invoking check_limit on newly constructed parents,
  link_count should not be set, but instead incremented by as many
  number of new invocations of check_limit.
* decrementing link_count and the check whether the count has hit zero
  to resume the waiting call_stub should be atomic.

Change-Id: I6f52e50547362a5ded6bd9f085570223aea372d1
BUG: 969461
Signed-off-by: Raghavendra G <rgowdapp@redhat.com>
Reviewed-on: http://review.gluster.org/6491
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

1 files changed, 68 insertions, 53 deletions

diff --git a/xlators/features/quota/src/quota.c b/xlators/features/quota/src/quota.c
index 0af514cef0c..e1471258b49 100644
--- a/xlators/features/quota/src/quota.c
+++ b/xlators/features/quota/src/quota.c
@@ -245,7 +245,7 @@ out:
 }
 
 inline void
-quota_resume_fop_if_validation_done (quota_local_t *local)
+quota_link_count_decrement (quota_local_t *local)
 {
         call_stub_t *stub       = NULL;
         int          link_count = -1;
@@ -255,7 +255,7 @@ quota_resume_fop_if_validation_done (quota_local_t *local)
 
         LOCK (&local->lock);
         {
-                link_count = local->link_count;
+                link_count = --local->link_count;
                 if (link_count == 0) {
                         stub = local->stub;
                         local->stub = NULL;
@@ -283,13 +283,11 @@ quota_handle_validate_error (quota_local_t *local, int32_t op_ret,
                         local->op_ret = op_ret;
                         local->op_errno = op_errno;
                 }
-
-                /* we abort checking limits on this path to root */
-                local->link_count--;
         }
         UNLOCK (&local->lock);
 
-        quota_resume_fop_if_validation_done (local);
+        /* we abort checking limits on this path to root */
+        quota_link_count_decrement (local);
 out:
         return;
 }
@@ -795,12 +793,8 @@ quota_check_limit (call_frame_t *frame, inode_t *inode, xlator_t *this,
          */
         if (0 > frame->root->pid) {
                 ret = 0;
-		LOCK (&local->lock);
-		{
-			--local->link_count;
-		}
-		UNLOCK (&local->lock);
-                goto resume;
+                quota_link_count_decrement (local);
+                goto done;
         }
 
         priv = this->private;
@@ -883,12 +877,7 @@ quota_check_limit (call_frame_t *frame, inode_t *inode, xlator_t *this,
                 }
 
                 if (__is_root_gfid (_inode->gfid)) {
-                        LOCK (&local->lock);
-                        {
-                                --local->link_count;
-                        }
-                        UNLOCK (&local->lock);
-
+                        quota_link_count_decrement (local);
                         break;
                 }
 
@@ -929,8 +918,7 @@ quota_check_limit (call_frame_t *frame, inode_t *inode, xlator_t *this,
                 _inode = NULL;
         }
 
-resume:
-        quota_resume_fop_if_validation_done (local);
+done:
         return 0;
 
 err:
@@ -1303,13 +1291,18 @@ quota_writev (call_frame_t *frame, xlator_t *this, fd_t *fd,
                 UNLOCK (&ctx->lock);
         }
 
-        local->delta = size;
-
-        local->link_count = parents;
-        local->stub = stub;
+        LOCK (&local->lock);
+        {
+                local->delta = size;
+                local->link_count = (parents != 0) ? parents : 1;
+                local->stub = stub;
+        }
+        UNLOCK (&local->lock);
 
         if (parents == 0) {
-                local->link_count = 1;
+                /* nameless lookup on this inode, allow quota to reconstruct
+                 * ancestry as part of check_limit.
+                 */
                 quota_check_limit (frame, fd->inode, this, NULL, NULL);
         } else {
                 list_for_each_entry_safe (dentry, tmp, &head, next) {
@@ -1412,9 +1405,13 @@ quota_mkdir (call_frame_t *frame, xlator_t *this, loc_t *loc, mode_t mode,
                 goto err;
         }
 
-        local->stub = stub;
-        local->delta = 0;
-        local->link_count = 1;
+        LOCK (&local->lock);
+        {
+                local->stub = stub;
+                local->delta = 0;
+                local->link_count = 1;
+        }
+        UNLOCK (&local->lock);
 
         quota_check_limit (frame, loc->parent, this, NULL, NULL);
         return 0;
@@ -1557,9 +1554,13 @@ quota_create (call_frame_t *frame, xlator_t *this, loc_t *loc, int32_t flags,
                 goto err;
         }
 
-        local->link_count = 1;
-        local->stub = stub;
-        local->delta = 0;
+        LOCK (&local->lock);
+        {
+                local->link_count = 1;
+                local->stub = stub;
+                local->delta = 0;
+        }
+        UNLOCK (&local->lock);
 
         quota_check_limit (frame, loc->parent, this, NULL, NULL);
         return 0;
@@ -1829,9 +1830,13 @@ quota_link (call_frame_t *frame, xlator_t *this, loc_t *oldloc, loc_t *newloc,
                 goto err;
         }
 
-        local->link_count = 1;
-        local->stub = stub;
-        local->delta = (ctx != NULL) ? ctx->buf.ia_blocks * 512 : 0;
+        LOCK (&local->lock);
+        {
+                local->link_count = 1;
+                local->stub = stub;
+                local->delta = (ctx != NULL) ? ctx->buf.ia_blocks * 512 : 0;
+        }
+        UNLOCK (&local->lock);
 
         quota_check_limit (frame, newloc->parent, this, NULL, NULL);
         return 0;
@@ -2072,8 +2077,12 @@ quota_rename (call_frame_t *frame, xlator_t *this, loc_t *oldloc,
                 goto err;
         }
 
-        local->link_count = 1;
-        local->stub = stub;
+        LOCK (&local->lock);
+        {
+                local->link_count = 1;
+                local->stub = stub;
+        }
+        UNLOCK (&local->lock);
 
         if (QUOTA_REG_OR_LNK_FILE (oldloc->inode->ia_type)) {
                 ret = quota_inode_ctx_get (oldloc->inode, this, &ctx, 0);
@@ -2248,9 +2257,13 @@ quota_symlink (call_frame_t *frame, xlator_t *this, const char *linkpath,
                 goto err;
         }
 
-        local->stub = stub;
-        local->delta = strlen (linkpath);
-        local->link_count = 1;
+        LOCK (&local->lock);
+        {
+                local->stub = stub;
+                local->delta = strlen (linkpath);
+                local->link_count = 1;
+        }
+        UNLOCK (&local->lock);
 
         quota_check_limit (frame, loc->parent, this, NULL, NULL);
         return 0;
@@ -3207,9 +3220,13 @@ quota_mknod (call_frame_t *frame, xlator_t *this, loc_t *loc, mode_t mode,
                 goto err;
         }
 
-        local->link_count = 1;
-        local->stub = stub;
-        local->delta = 0;
+        LOCK (&local->lock);
+        {
+                local->link_count = 1;
+                local->stub = stub;
+                local->delta = 0;
+        }
+        UNLOCK (&local->lock);
 
         quota_check_limit (frame, loc->parent, this, NULL, NULL);
         return 0;
@@ -3655,9 +3672,7 @@ quota_statfs_validate_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
         UNLOCK (&ctx->lock);
 
 resume:
-        --local->link_count;
-
-        quota_resume_fop_if_validation_done (local);
+        quota_link_count_decrement (local);
         return 0;
 }
 
@@ -3682,26 +3697,26 @@ quota_statfs (call_frame_t *frame, xlator_t *this, loc_t *loc, dict_t *xdata)
                 }
                 frame->local = local;
 
-                local->inode = inode_ref (loc->inode);
-                local->link_count = 1;
-
                 stub = fop_statfs_stub (frame, quota_statfs_helper, loc, xdata);
                 if (!stub) {
                         op_errno = ENOMEM;
                         goto err;
                 }
 
-                local->stub = stub;
+                LOCK (&local->lock);
+                {
+                        local->inode = inode_ref (loc->inode);
+                        local->link_count = 1;
+                        local->stub = stub;
+                }
+                UNLOCK (&local->lock);
 
                 ret = quota_validate (frame, local->inode, this,
                                       quota_statfs_validate_cbk);
                 if (0 > ret) {
-                        op_errno = -ret;
-                        --local->link_count;
+                        quota_handle_validate_error (local, -1, -ret);
                 }
 
-                quota_resume_fop_if_validation_done (local);
-
                 return 0;
 	}