cluster/afr: Handle NULL fdctx in fsync

Problem:
If fdctx is NULL in afr_fsync, process crashes because
of NULL dereference.

Fix:
if fdctx is NULL, always say witnessed unstable write so
that fsyncs are done properly. Handled fdctx being null
in afr_delayed_changelog_post_op otherwise fsync stub is
never resumed and the mount was hanging.

Change-Id: Icacc900e9be63c29db3325cb0e19cc250adebaac
BUG: 978794
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5258
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

2 files changed, 33 insertions, 1 deletions

diff --git a/tests/bugs/bug-978794.t b/tests/bugs/bug-978794.t
new file mode 100644
index 000000000..d22d3cde3
--- /dev/null
+++ b/tests/bugs/bug-978794.t
@@ -0,0 +1,29 @@
+#!/bin/bash
+. $(dirname $0)/../include.rc
+. $(dirname $0)/../volume.rc
+. $(dirname $0)/../fileio.rc
+
+
+# This test opens 100 fds and triggers graph switches to check if fsync
+# as part of graph-switch causes crash or not.
+
+cleanup;
+
+TEST glusterd
+TEST pidof glusterd
+TEST $CLI volume create $V0 replica 2 $H0:$B0/${V0}{0,1}
+TEST $CLI volume start $V0
+TEST glusterfs --volfile-id=/$V0 --volfile-server=$H0 $M0
+TEST touch $M0/{1..100}
+for i in {1..100}; do fd[$i]=`fd_available`; fd_open ${fd[$i]} 'w' $M0/$i; done
+TEST $CLI volume add-brick $V0 $H0:$B0/${V0}{2,3}
+TEST $CLI volume rebalance $V0 start force
+EXPECT_WITHIN 120 "completed" rebalance_status_field $V0
+TEST cat $M0/{1..100}
+for i in {1..100}; do fd_write ${fd[$i]} 'abc'; done
+TEST $CLI volume add-brick $V0 $H0:$B0/${V0}{4,5}
+TEST $CLI volume rebalance $V0 start force
+EXPECT_WITHIN 120 "completed" rebalance_status_field $V0
+for i in {1..100}; do fd_write ${fd[$i]} 'abc'; done
+TEST cat $M0/{1..100}
+cleanup
diff --git a/xlators/cluster/afr/src/afr-transaction.c b/xlators/cluster/afr/src/afr-transaction.c
index 8f3673ace..0ae4fe477 100644
--- a/xlators/cluster/afr/src/afr-transaction.c
+++ b/xlators/cluster/afr/src/afr-transaction.c
@@ -1402,6 +1402,8 @@ afr_fd_has_witnessed_unstable_write (xlator_t *this, fd_t *fd)
 	gf_boolean_t witness = _gf_false;
 
 	fdctx = afr_fd_ctx_get (fd, this);
+        if (!fdctx)
+                return _gf_true;
 
 	LOCK(&fd->lock);
 	{
@@ -1568,7 +1570,7 @@ afr_delayed_changelog_post_op (xlator_t *this, call_frame_t *frame, fd_t *fd,
 
 	fd_ctx = afr_fd_ctx_get (fd, this);
 	if (!fd_ctx)
-		return;
+                goto out;
 
 	delta.tv_sec = priv->post_op_delay_secs;
 	delta.tv_usec = 0;
@@ -1590,6 +1592,7 @@ afr_delayed_changelog_post_op (xlator_t *this, call_frame_t *frame, fd_t *fd,
 unlock:
 	pthread_mutex_unlock (&fd_ctx->delay_lock);
 
+out:
 	if (prev_frame) {
 		local = prev_frame->local;
 		local->transaction.resume_stub = stub;