[sheepdog] [PATCH] sheep: set cluster_op_running to false after block request finishes

[MORITA Kazutaka]

From: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>

There is a race problem that sd_block_handler() can be executed before
sd_notify_handler() of the previous block request.  This leads to
segmentation fault.  For example,

 1. There are two requests in pending_block_list.

 2. sd_block_handler() of the first block request is called.
    cluster_op_running is set to true.

 3. cluster_op_done of the first block request is called and
    cluster_op_running is set to false.

 4. sd_block_handler() of the second block request is tried to be
    called.  However, the first one is still in the pending_block_list
    and sd_block_handler() is called against the first request again.

To fix this problem, this patch sets cluster_op_running to false after
the request is removed from the pending_block_list in
sd_notify_handler().

Signed-off-by: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
---
 sheep/group.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sheep/group.c b/sheep/group.c
index fe45ff9..b9399ee 100644
--- a/sheep/group.c
+++ b/sheep/group.c
@@ -272,8 +272,6 @@ static void cluster_op_done(struct work *work)
 	struct vdi_op_message *msg;
 	size_t size;
 
-	cluster_op_running = false;
-
 	sd_dprintf("%s (%p)", op_name(req->op), req);
 
 	msg = prepare_cluster_msg(req, &size);
@@ -976,6 +974,9 @@ void sd_notify_handler(const struct sd_node *sender, void *data,
 
 		put_request(req);
 	}
+
+	if (has_process_work(op))
+		cluster_op_running = false;
 }
 
 enum cluster_join_result sd_check_join_cb(const struct sd_node *joining,
-- 
1.7.9.5