ceph: fix message length computation

create_request_message() computes the maximum length of a message,
but uses the wrong type for the time stamp: sizeof(struct timespec)
may be 8 or 16 depending on the architecture, while sizeof(struct
ceph_timespec) is always 8, and that is what gets put into the
message.

Found while auditing the uses of timespec for y2038 problems.

Fixes: b8e69066 ("ceph: include time stamp in every MDS request")
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NYan, Zheng <zyan@redhat.com>

fs/ceph/mds_client.c

@@ -1935,7 +1935,7 @@ static struct ceph_msg *create_request_message(struct ceph_mds_client *mdsc,
 
 	len = sizeof(*head) +
 		pathlen1 + pathlen2 + 2*(1 + sizeof(u32) + sizeof(u64)) +
-		sizeof(struct timespec);
+		sizeof(struct ceph_timespec);
 
 	/* calculate (max) length for cap releases */
 	len += sizeof(struct ceph_mds_request_release) *