[ 214/221] ceph: Fix infinite loop in __wake_requests

[Greg Kroah-Hartman]

3.7-stable review patch.  If anyone has any objections, please let me know.

------------------


From: "Yan, Zheng" <zheng.z.yan@xxxxxxxxx>

(cherry picked from commit ed75ec2cd19b47efcd292b6e23f58e56f4c5bc34)

__wake_requests() will enter infinite loop if we use it to wake
requests in the session->s_waiting list. __wake_requests() deletes
requests from the list and __do_request() adds requests back to
the list.

Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
Signed-off-by: Sage Weil <sage@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/ceph/mds_client.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1876,9 +1876,14 @@ finish:
 static void __wake_requests(struct ceph_mds_client *mdsc,
 			    struct list_head *head)
 {
-	struct ceph_mds_request *req, *nreq;
+	struct ceph_mds_request *req;
+	LIST_HEAD(tmp_list);
 
-	list_for_each_entry_safe(req, nreq, head, r_wait) {
+	list_splice_init(head, &tmp_list);
+
+	while (!list_empty(&tmp_list)) {
+		req = list_entry(tmp_list.next,
+				 struct ceph_mds_request, r_wait);
 		list_del_init(&req->r_wait);
 		__do_request(mdsc, req);
 	}


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