libceph: isolate message page field manipulation

Define a function ceph_msg_data_set_pages(), which more clearly
abstracts the assignment page-related fields for data in a ceph
message structure.  Use this new function in the osd client and mds
client.

Ideally, these fields would never be set more than once (with
BUG_ON() calls to guarantee that).  At the moment though the osd
client sets these every time it receives a message, and in the event
of a communication problem this can happen more than once.  (This
will be resolved shortly, but setting up these helpers first makes
it all a bit easier to work with.)

Rearrange the field order in a ceph_msg structure to group those
that are used to define the possible data payloads.

This partially resolves:
    http://tracker.ceph.com/issues/4263

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

2 files changed, 15 insertions, 6 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index ce1669f75ca5..cec39cb623f0 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2689,6 +2689,17 @@ void ceph_con_keepalive(struct ceph_connection *con)
 }
 EXPORT_SYMBOL(ceph_con_keepalive);
 
+void ceph_msg_data_set_pages(struct ceph_msg *msg, struct page **pages,
+                unsigned int page_count, size_t alignment)
+{
+        /* BUG_ON(msg->pages); */
+        /* BUG_ON(msg->page_count); */
+
+        msg->pages = pages;
+        msg->page_count = page_count;
+        msg->page_alignment = alignment & ~PAGE_MASK;
+}
+EXPORT_SYMBOL(ceph_msg_data_set_pages);
 
 /*
  * construct a new message with given type, size
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 202af14dc6dc..a09d57134075 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -1760,11 +1760,10 @@ int ceph_osdc_start_request(struct ceph_osd_client *osdc,
         if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGES) {
                 unsigned int page_count;
 
-                req->r_request->pages = osd_data->pages;
                 page_count = calc_pages_for((u64)osd_data->alignment,
                                                 (u64)osd_data->length);
-                req->r_request->page_count = page_count;
-                req->r_request->page_alignment = osd_data->alignment;
+                ceph_msg_data_set_pages(req->r_request, osd_data->pages,
+                        page_count, osd_data->alignment);
 #ifdef CONFIG_BLOCK
         } else if (osd_data->type == CEPH_OSD_DATA_TYPE_BIO) {
                 req->r_request->bio = osd_data->bio;
@@ -2135,9 +2134,8 @@ static struct ceph_msg *get_reply(struct ceph_connection *con,
                         }
                         page_count = calc_pages_for((u64)osd_data->alignment,
                                                         (u64)osd_data->length);
-                        m->pages = osd_data->pages;
-                        m->page_count = page_count;
-                        m->page_alignment = osd_data->alignment;
+                        ceph_msg_data_set_pages(m, osd_data->pages,
+                                osd_data->num_pages, osd_data->alignment);
 #ifdef CONFIG_BLOCK
                 } else if (osd_data->type == CEPH_OSD_DATA_TYPE_BIO) {
                         m->bio = osd_data->bio;