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>

1 files changed, 13 insertions, 9 deletions

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 6c118748a7f8..aa463b9b30af 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -74,21 +74,22 @@ struct ceph_msg {
 	struct ceph_msg_footer footer;	/* footer */
 	struct kvec front;              /* unaligned blobs of message */
 	struct ceph_buffer *middle;
-	struct page **pages;            /* data payload.  NOT OWNER. */
-	unsigned page_count;		/* size of page array */
-	unsigned page_alignment;        /* io offset in first page */
-	struct ceph_pagelist *pagelist; /* instead of pages */
-
-	struct ceph_connection *con;
-	struct list_head list_head;
 
-	struct kref kref;
+	struct page **pages;		/* data payload.  NOT OWNER. */
+	unsigned int page_alignment;	/* io offset in first page */
+	unsigned int page_count;	/* # pages in array or list */
+	struct ceph_pagelist *pagelist; /* instead of pages */
 #ifdef CONFIG_BLOCK
+	unsigned int bio_seg;		/* current bio segment */
 	struct bio  *bio;		/* instead of pages/pagelist */
 	struct bio  *bio_iter;		/* bio iterator */
-	unsigned int bio_seg;		/* current bio segment */
 #endif /* CONFIG_BLOCK */
 	struct ceph_pagelist *trail;	/* the trailing part of the data */
+
+	struct ceph_connection *con;
+	struct list_head list_head;	/* links for connection lists */
+
+	struct kref kref;
 	bool front_is_vmalloc;
 	bool more_to_follow;
 	bool needs_out_seq;
@@ -218,6 +219,9 @@ extern void ceph_msg_revoke_incoming(struct ceph_msg *msg);
 
 extern void ceph_con_keepalive(struct ceph_connection *con);
 
+extern void ceph_msg_data_set_pages(struct ceph_msg *msg, struct page **pages,
+				unsigned int page_count, size_t alignment);
+
 extern struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags,
 				     bool can_fail);
 extern void ceph_msg_kfree(struct ceph_msg *m);