ceph: explicitly specify page alignment in network messages

The alignment used for reading data into or out of pages used to be taken
from the data_off field in the message header.  This only worked as long
as the page alignment matched the object offset, breaking direct io to
non-page aligned offsets.

Instead, explicitly specify the page alignment next to the page vector
in the ceph_msg struct, and use that instead of the message header (which
probably shouldn't be trusted).  The alloc_msg callback is responsible for
filling in this field properly when it sets up the page vector.

Signed-off-by: Sage Weil <sage@newdream.net>

3 files changed, 9 insertions, 5 deletions

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 5956d62c3057..a108b425fee2 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -82,6 +82,7 @@ struct ceph_msg {
         struct ceph_buffer *middle;
         struct page **pages;            /* data payload.  NOT OWNER. */
         unsigned nr_pages;              /* size of page array */
+        unsigned page_alignment;        /* io offset in first page */
         struct ceph_pagelist *pagelist; /* instead of pages */
         struct list_head list_head;
         struct kref kref;
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index d379abf873bc..1c7a2ec4f3cc 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -540,8 +540,7 @@ static void prepare_write_message(struct ceph_connection *con)
                 /* initialize page iterator */
                 con->out_msg_pos.page = 0;
                 if (m->pages)
-                        con->out_msg_pos.page_pos =
-                                le16_to_cpu(m->hdr.data_off) & ~PAGE_MASK;
+                        con->out_msg_pos.page_pos = m->page_alignment;
                 else
                         con->out_msg_pos.page_pos = 0;
                 con->out_msg_pos.data_pos = 0;
@@ -1491,7 +1490,7 @@ static int read_partial_message(struct ceph_connection *con)
         struct ceph_msg *m = con->in_msg;
         int ret;
         int to, left;
-        unsigned front_len, middle_len, data_len, data_off;
+        unsigned front_len, middle_len, data_len;
         int datacrc = con->msgr->nocrc;
         int skip;
         u64 seq;
@@ -1527,7 +1526,6 @@ static int read_partial_message(struct ceph_connection *con)
         data_len = le32_to_cpu(con->in_hdr.data_len);
         if (data_len > CEPH_MSG_MAX_DATA_LEN)
                 return -EIO;
-        data_off = le16_to_cpu(con->in_hdr.data_off);
 
         /* verify seq# */
         seq = le64_to_cpu(con->in_hdr.seq);
@@ -1575,7 +1573,7 @@ static int read_partial_message(struct ceph_connection *con)
 
                 con->in_msg_pos.page = 0;
                 if (m->pages)
-                        con->in_msg_pos.page_pos = data_off & ~PAGE_MASK;
+                        con->in_msg_pos.page_pos = m->page_alignment;
                 else
                         con->in_msg_pos.page_pos = 0;
                 con->in_msg_pos.data_pos = 0;
@@ -2300,6 +2298,7 @@ struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags)
 
         /* data */
         m->nr_pages = 0;
+        m->page_alignment = 0;
         m->pages = NULL;
         m->pagelist = NULL;
         m->bio = NULL;
@@ -2369,6 +2368,7 @@ static struct ceph_msg *ceph_alloc_msg(struct ceph_connection *con,
                                type, front_len);
                         return NULL;
                 }
+                msg->page_alignment = le16_to_cpu(hdr->data_off);
         }
         memcpy(&msg->hdr, &con->in_hdr, sizeof(con->in_hdr));
 
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 6c096239660c..3e20a122ffa2 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -391,6 +391,8 @@ void ceph_osdc_build_request(struct ceph_osd_request *req,
                 req->r_request->hdr.data_len = cpu_to_le32(data_len);
         }
 
+        req->r_request->page_alignment = req->r_page_alignment;
+
         BUG_ON(p > msg->front.iov_base + msg->front.iov_len);
         msg_size = p - msg->front.iov_base;
         msg->front.iov_len = msg_size;
@@ -1657,6 +1659,7 @@ static struct ceph_msg *get_reply(struct ceph_connection *con,
                 }
                 m->pages = req->r_pages;
                 m->nr_pages = req->r_num_pages;
+                m->page_alignment = req->r_page_alignment;
 #ifdef CONFIG_BLOCK
                 m->bio = req->r_bio;
 #endif