libceph: small changes to messenger.c

This patch gathers a few small changes in "net/ceph/messenger.c":
  out_msg_pos_next()
    - small logic change that mostly affects indentation
  write_partial_msg_pages().
    - use a local variable trail_off to represent the offset into
      a message of the trail portion of the data (if present)
    - once we are in the trail portion we will always be there, so we
      don't always need to check against our data position
    - avoid computing len twice after we've reached the trail
    - get rid of the variable tmpcrc, which is not needed
    - trail_off and trail_len never change so mark them const
    - update some comments
  read_partial_message_bio()
    - bio_iovec_idx() will never return an error, so don't bother
      checking for it

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

1 files changed, 31 insertions, 32 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 32a3a2a72580..4578e99bbef1 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -907,21 +907,23 @@ static void out_msg_pos_next(struct ceph_connection *con, struct page *page,
 
         con->out_msg_pos.data_pos += sent;
         con->out_msg_pos.page_pos += sent;
-        if (sent == len) {
-                con->out_msg_pos.page_pos = 0;
-                con->out_msg_pos.page++;
-                con->out_msg_pos.did_page_crc = false;
-                if (in_trail)
-                        list_move_tail(&page->lru,
-                                       &msg->trail->head);
-                else if (msg->pagelist)
-                        list_move_tail(&page->lru,
-                                       &msg->pagelist->head);
+        if (sent < len)
+                return;
+
+        BUG_ON(sent != len);
+        con->out_msg_pos.page_pos = 0;
+        con->out_msg_pos.page++;
+        con->out_msg_pos.did_page_crc = false;
+        if (in_trail)
+                list_move_tail(&page->lru,
+                               &msg->trail->head);
+        else if (msg->pagelist)
+                list_move_tail(&page->lru,
+                               &msg->pagelist->head);
 #ifdef CONFIG_BLOCK
-                else if (msg->bio)
-                        iter_bio_next(&msg->bio_iter, &msg->bio_seg);
+        else if (msg->bio)
+                iter_bio_next(&msg->bio_iter, &msg->bio_seg);
 #endif
-        }
 }
 
 /*
@@ -940,30 +942,31 @@ static int write_partial_msg_pages(struct ceph_connection *con)
         int ret;
         int total_max_write;
         bool in_trail = false;
-        size_t trail_len = (msg->trail ? msg->trail->length : 0);
+        const size_t trail_len = (msg->trail ? msg->trail->length : 0);
+        const size_t trail_off = data_len - trail_len;
 
         dout("write_partial_msg_pages %p msg %p page %d/%d offset %d\n",
              con, msg, con->out_msg_pos.page, msg->nr_pages,
              con->out_msg_pos.page_pos);
 
+        /*
+         * Iterate through each page that contains data to be
+         * written, and send as much as possible for each.
+         *
+         * If we are calculating the data crc (the default), we will
+         * need to map the page.  If we have no pages, they have
+         * been revoked, so use the zero page.
+         */
         while (data_len > con->out_msg_pos.data_pos) {
                 struct page *page = NULL;
                 int max_write = PAGE_SIZE;
                 int bio_offset = 0;
 
-                total_max_write = data_len - trail_len -
-                        con->out_msg_pos.data_pos;
-
-                /*
-                 * if we are calculating the data crc (the default), we need
-                 * to map the page.  if our pages[] has been revoked, use the
-                 * zero page.
-                 */
-
-                /* have we reached the trail part of the data? */
-                if (con->out_msg_pos.data_pos >= data_len - trail_len) {
-                        in_trail = true;
+                in_trail = in_trail || con->out_msg_pos.data_pos >= trail_off;
+                if (!in_trail)
+                        total_max_write = trail_off - con->out_msg_pos.data_pos;
 
+                if (in_trail) {
                         total_max_write = data_len - con->out_msg_pos.data_pos;
 
                         page = list_first_entry(&msg->trail->head,
@@ -990,14 +993,13 @@ static int write_partial_msg_pages(struct ceph_connection *con)
 
                 if (do_datacrc && !con->out_msg_pos.did_page_crc) {
                         void *base;
-                        u32 crc;
-                        u32 tmpcrc = le32_to_cpu(msg->footer.data_crc);
+                        u32 crc = le32_to_cpu(msg->footer.data_crc);
                         char *kaddr;
 
                         kaddr = kmap(page);
                         BUG_ON(kaddr == NULL);
                         base = kaddr + con->out_msg_pos.page_pos + bio_offset;
-                        crc = crc32c(tmpcrc, base, len);
+                        crc = crc32c(crc, base, len);
                         msg->footer.data_crc = cpu_to_le32(crc);
                         con->out_msg_pos.did_page_crc = true;
                 }
@@ -1702,9 +1704,6 @@ static int read_partial_message_bio(struct ceph_connection *con,
         void *p;
         int ret, left;
 
-        if (IS_ERR(bv))
-                return PTR_ERR(bv);
-
         left = min((int)(data_len - con->in_msg_pos.data_pos),
                    (int)(bv->bv_len - con->in_msg_pos.page_pos));