ceph: only set message data pointers if non-empty

Change it so we only assign outgoing data information for messages
if there is outgoing data to send.

This then allows us to add a few more (currently commented-out)
assertions.

This is related to:
    http://tracker.ceph.com/issues/4284

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Greg Farnum <greg@inktank.com>

3 files changed, 20 insertions, 6 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 3b2aa8702ae0..600d770d70f7 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1721,7 +1721,11 @@ static struct ceph_msg *create_request_message(struct ceph_mds_client *mdsc,
         msg->front.iov_len = p - msg->front.iov_base;
         msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
 
-        ceph_msg_data_set_pages(msg, req->r_pages, req->r_data_len, 0);
+        if (req->r_data_len) {
+                /* outbound data set only by ceph_sync_setxattr() */
+                BUG_ON(!req->r_pages);
+                ceph_msg_data_set_pages(msg, req->r_pages, req->r_data_len, 0);
+        }
 
         msg->hdr.data_len = cpu_to_le32(req->r_data_len);
         msg->hdr.data_off = cpu_to_le16(0);
@@ -2603,10 +2607,13 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc,
                         goto fail;
         }
 
-        ceph_msg_data_set_pagelist(reply, pagelist);
         if (recon_state.flock)
                 reply->hdr.version = cpu_to_le16(2);
-        reply->hdr.data_len = cpu_to_le32(pagelist->length);
+        if (pagelist->length) {
+                /* set up outbound data if we have any */
+                reply->hdr.data_len = cpu_to_le32(pagelist->length);
+                ceph_msg_data_set_pagelist(reply, pagelist);
+        }
         ceph_con_send(&session->s_con, reply);
 
         mutex_unlock(&session->s_mutex);
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index d1183536d5a8..1965d785cf83 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2692,6 +2692,8 @@ EXPORT_SYMBOL(ceph_con_keepalive);
 void ceph_msg_data_set_pages(struct ceph_msg *msg, struct page **pages,
                 size_t length, size_t alignment)
 {
+        /* BUG_ON(!pages); */
+        /* BUG_ON(!length); */
         /* BUG_ON(msg->pages); */
         /* BUG_ON(msg->page_count); */
 
@@ -2705,6 +2707,7 @@ void ceph_msg_data_set_pagelist(struct ceph_msg *msg,
                                 struct ceph_pagelist *pagelist)
 {
         /* BUG_ON(!pagelist); */
+        /* BUG_ON(!pagelist->length); */
         /* BUG_ON(msg->pagelist); */
 
         msg->pagelist = pagelist;
@@ -2723,6 +2726,7 @@ EXPORT_SYMBOL(ceph_msg_data_set_bio);
 void ceph_msg_data_set_trail(struct ceph_msg *msg, struct ceph_pagelist *trail)
 {
         /* BUG_ON(!trail); */
+        /* BUG_ON(!trail->length); */
         /* BUG_ON(msg->trail); */
 
         msg->trail = trail;
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 387e3123d1ed..4402e917b9b1 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -1759,8 +1759,10 @@ int ceph_osdc_start_request(struct ceph_osd_client *osdc,
         osd_data = &req->r_data_out;
         if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGES) {
                 BUG_ON(osd_data->length > (u64) SIZE_MAX);
-                ceph_msg_data_set_pages(req->r_request, osd_data->pages,
-                        osd_data->length, osd_data->alignment);
+                if (osd_data->length)
+                        ceph_msg_data_set_pages(req->r_request,
+                                osd_data->pages, osd_data->length,
+                                osd_data->alignment);
 #ifdef CONFIG_BLOCK
         } else if (osd_data->type == CEPH_OSD_DATA_TYPE_BIO) {
                 ceph_msg_data_set_bio(req->r_request, osd_data->bio);
@@ -1768,7 +1770,8 @@ int ceph_osdc_start_request(struct ceph_osd_client *osdc,
         } else {
                 BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_NONE);
         }
-        ceph_msg_data_set_trail(req->r_request, &req->r_trail);
+        if (req->r_trail.length)
+                ceph_msg_data_set_trail(req->r_request, &req->r_trail);
 
         register_request(osdc, req);