afr: handle short writes in afr_writev_wind and self-heal to avoid corruption

The current failure to handle short writes on writev fops leaves
us open to file corruption. A short write on a user request is
ignored and leaves replicas in an inconsistent state. A short write
during a self-heal is ignored and incorrectly marks the files as
consistent if the heal completes.

Modify user writev handling to return the best case return value
from each of the replicas. Short writes that occur relative to this
value are marked as failed and will require a heal. Modify
self-heal to set an error on a short write and abort the heal.

BUG: 853690
Change-Id: I18b30f58702326249230eeebb361b29e40b535f5
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-on: http://review.gluster.org/4150
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>

1 files changed, 46 insertions, 15 deletions

diff --git a/xlators/cluster/afr/src/afr-inode-write.c b/xlators/cluster/afr/src/afr-inode-write.c
index 94700ddae..d9d3800fc 100644
--- a/xlators/cluster/afr/src/afr-inode-write.c
+++ b/xlators/cluster/afr/src/afr-inode-write.c
@@ -77,8 +77,11 @@ afr_writev_wind_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
         int child_index = (long) cookie;
         int call_count  = -1;
         int read_child  = 0;
+	afr_private_t *priv = NULL;
+	int i = 0;
 
         local = frame->local;
+	priv = this->private;
 
         read_child = afr_inode_get_read_ctx (this, local->fd->inode, NULL);
 
@@ -88,31 +91,50 @@ afr_writev_wind_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
                         local->read_child_returned = _gf_true;
                 }
 
+		local->replies[child_index].valid = 1;
+		local->replies[child_index].op_ret = op_ret;
+		local->replies[child_index].op_errno = op_errno;
+
                 if (afr_fop_failed (op_ret, op_errno))
                         afr_transaction_fop_failed (frame, this, child_index);
 
-                if (op_ret != -1) {
-                        if (local->success_count == 0) {
-                                local->op_ret              = op_ret;
-                                local->cont.writev.prebuf  = *prebuf;
-                                local->cont.writev.postbuf = *postbuf;
-                        }
-
-                        if (child_index == read_child) {
-                                local->cont.writev.prebuf  = *prebuf;
-                                local->cont.writev.postbuf = *postbuf;
-                        }
-                }
-
-                local->op_errno = op_errno;
+		/* stage the best case return value for unwind */
+                if ((local->success_count == 0) || (op_ret > local->op_ret)) {
+                        local->op_ret              = op_ret;
+			local->op_errno		   = op_errno;
+		}
+
+		if (op_ret != -1) {
+			if ((local->success_count == 0) ||
+			    (child_index == read_child)) {
+				local->cont.writev.prebuf  = *prebuf;
+				local->cont.writev.postbuf = *postbuf;
+			}
+			local->success_count++;
+		}
         }
         UNLOCK (&frame->lock);
 
         call_count = afr_frame_return (frame);
 
         if (call_count == 0) {
-                local->transaction.unwind (frame, this);
+		/*
+		 * We already have the best case result of the writev calls staged
+		 * as the return value. Any writev that returns some value less
+		 * than the best case is now out of sync, so mark the fop as
+		 * failed. Note that fops that have returned with errors have
+		 * already been marked as failed.
+		 */
+		for (i = 0; i < priv->child_count; i++) {
+			if ((!local->replies[i].valid) ||
+			    (local->replies[i].op_ret == -1))
+				continue;
+
+			if (local->replies[i].op_ret < local->op_ret)
+				afr_transaction_fop_failed(frame, this, i);
+		}
 
+                local->transaction.unwind (frame, this);
                 local->transaction.resume (frame, this);
         }
         return 0;
@@ -138,6 +160,15 @@ afr_writev_wind (call_frame_t *frame, xlator_t *this)
         }
 
         local->call_count = call_count;
+	local->replies = GF_CALLOC(priv->child_count, sizeof(*local->replies),
+				   gf_afr_mt_reply_t);
+	if (!local->replies) {
+		local->op_ret = -1;
+		local->op_errno = ENOMEM;
+		local->transaction.unwind(frame, this);
+		local->transaction.resume(frame, this);
+		return 0;
+	}
 
         for (i = 0; i < priv->child_count; i++) {
                 if (local->transaction.pre_op[i]) {