libceph: kill last of ceph_msg_pos

The only remaining field in the ceph_msg_pos structure is
did_page_crc.  In the new cursor model of things that flag (or
something like it) belongs in the cursor.

Define a new field "need_crc" in the cursor (which applies to all
types of data) and initialize it to true whenever a cursor is
initialized.

In write_partial_message_data(), the data CRC still will be computed
as before, but it will check the cursor->need_crc field to determine
whether it's needed.  Any time the cursor is advanced to a new piece
of a data item, need_crc will be set, and this will cause the crc
for that entire piece to be accumulated into the data crc.

In write_partial_message_data() the intermediate crc value is now
held in a local variable so it doesn't have to be byte-swapped so
many times.  In read_partial_msg_data() we do something similar
(but mainly for consistency there).

With that, the ceph_msg_pos structure can go away,  and it no longer
needs to be passed as an argument to prepare_message_data().

This cleanup is related to:
    http://tracker.ceph.com/issues/4428

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

1 files changed, 31 insertions, 25 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 19f9fffc170c..eee7a878dbfb 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1002,6 +1002,7 @@ static void ceph_msg_data_cursor_init(struct ceph_msg_data *data,
                 /* BUG(); */
                 break;
         }
+        data->cursor.need_crc = true;
 }
 
 /*
@@ -1069,12 +1070,12 @@ static bool ceph_msg_data_advance(struct ceph_msg_data *data, size_t bytes)
                 BUG();
                 break;
         }
+        data->cursor.need_crc = new_piece;
 
         return new_piece;
 }
 
-static void prepare_message_data(struct ceph_msg *msg,
-                                struct ceph_msg_pos *msg_pos)
+static void prepare_message_data(struct ceph_msg *msg)
 {
         size_t data_len;
 
@@ -1086,8 +1087,6 @@ static void prepare_message_data(struct ceph_msg *msg,
         /* Initialize data cursor */
 
         ceph_msg_data_cursor_init(&msg->data, data_len);
-
-        msg_pos->did_page_crc = false;
 }
 
 /*
@@ -1186,7 +1185,7 @@ static void prepare_write_message(struct ceph_connection *con)
         /* is there a data payload? */
         con->out_msg->footer.data_crc = 0;
         if (m->hdr.data_len) {
-                prepare_message_data(con->out_msg, &con->out_msg_pos);
+                prepare_message_data(con->out_msg);
                 con->out_more = 1;  /* data + footer will follow */
         } else {
                 /* no, queue up footer too and be done */
@@ -1388,8 +1387,7 @@ static void out_msg_pos_next(struct ceph_connection *con, struct page *page,
                         size_t len, size_t sent)
 {
         struct ceph_msg *msg = con->out_msg;
-        struct ceph_msg_pos *msg_pos = &con->out_msg_pos;
-        bool need_crc = false;
+        bool need_crc;
 
         BUG_ON(!msg);
         BUG_ON(!sent);
@@ -1401,7 +1399,6 @@ static void out_msg_pos_next(struct ceph_connection *con, struct page *page,
                 return;
 
         BUG_ON(sent != len);
-        msg_pos->did_page_crc = false;
 }
 
 static void in_msg_pos_next(struct ceph_connection *con, size_t len,
@@ -1444,9 +1441,8 @@ static int write_partial_message_data(struct ceph_connection *con)
 {
         struct ceph_msg *msg = con->out_msg;
         struct ceph_msg_data_cursor *cursor = &msg->data.cursor;
-        struct ceph_msg_pos *msg_pos = &con->out_msg_pos;
         bool do_datacrc = !con->msgr->nocrc;
-        int ret;
+        u32 crc;
 
         dout("%s %p msg %p\n", __func__, con, msg);
 
@@ -1461,38 +1457,40 @@ static int write_partial_message_data(struct ceph_connection *con)
          * need to map the page.  If we have no pages, they have
          * been revoked, so use the zero page.
          */
+        crc = do_datacrc ? le32_to_cpu(msg->footer.data_crc) : 0;
         while (cursor->resid) {
                 struct page *page;
                 size_t page_offset;
                 size_t length;
                 bool last_piece;
+                int ret;
 
                 page = ceph_msg_data_next(&msg->data, &page_offset, &length,
                                                         &last_piece);
-                if (do_datacrc && !msg_pos->did_page_crc) {
-                        u32 crc = le32_to_cpu(msg->footer.data_crc);
+                if (do_datacrc && cursor->need_crc)
                         crc = ceph_crc32c_page(crc, page, page_offset, length);
-                        msg->footer.data_crc = cpu_to_le32(crc);
-                        msg_pos->did_page_crc = true;
-                }
                 ret = ceph_tcp_sendpage(con->sock, page, page_offset,
                                       length, last_piece);
-                if (ret <= 0)
-                        goto out;
+                if (ret <= 0) {
+                        if (do_datacrc)
+                                msg->footer.data_crc = cpu_to_le32(crc);
 
+                        return ret;
+                }
                 out_msg_pos_next(con, page, length, (size_t) ret);
         }
 
         dout("%s %p msg %p done\n", __func__, con, msg);
 
         /* prepare and queue up footer, too */
-        if (!do_datacrc)
+        if (do_datacrc)
+                msg->footer.data_crc = cpu_to_le32(crc);
+        else
                 msg->footer.flags |= CEPH_MSG_FOOTER_NOCRC;
         con_out_kvec_reset(con);
         prepare_write_message_footer(con);
-        ret = 1;
-out:
-        return ret;
+
+        return 1;       /* must return > 0 to indicate success */
 }
 
 /*
@@ -2144,24 +2142,32 @@ static int read_partial_msg_data(struct ceph_connection *con)
         struct page *page;
         size_t page_offset;
         size_t length;
+        u32 crc = 0;
         int ret;
 
         BUG_ON(!msg);
         if (WARN_ON(!ceph_msg_has_data(msg)))
                 return -EIO;
 
+        if (do_datacrc)
+                crc = con->in_data_crc;
         while (cursor->resid) {
                 page = ceph_msg_data_next(&msg->data, &page_offset, &length,
                                                         NULL);
                 ret = ceph_tcp_recvpage(con->sock, page, page_offset, length);
-                if (ret <= 0)
+                if (ret <= 0) {
+                        if (do_datacrc)
+                                con->in_data_crc = crc;
+
                         return ret;
+                }
 
                 if (do_datacrc)
-                        con->in_data_crc = ceph_crc32c_page(con->in_data_crc,
-                                                        page, page_offset, ret);
+                        crc = ceph_crc32c_page(crc, page, page_offset, ret);
                 in_msg_pos_next(con, length, ret);
         }
+        if (do_datacrc)
+                con->in_data_crc = crc;
 
         return 1;       /* must return > 0 to indicate success */
 }
@@ -2257,7 +2263,7 @@ static int read_partial_message(struct ceph_connection *con)
                 /* prepare for data payload, if any */
 
                 if (data_len)
-                        prepare_message_data(con->in_msg, &con->in_msg_pos);
+                        prepare_message_data(con->in_msg);
         }
 
         /* front */