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libceph: use data cursor for message pagelist 

Switch to using the message cursor for the (non-trail) outgoing
pagelist data item in a message if present.

Notes on the logic changes in out_msg_pos_next():
    - only the mds client uses a ceph pagelist for message data;
    - if the mds client ever uses a pagelist, it never uses a page
      array (or anything else, for that matter) for data in the same
      message;
    - only the osd client uses the trail portion of a message data,
      and when it does, it never uses any other data fields for
      outgoing data in the same message; and finally
    - only the rbd client uses bio message data (never pagelist).

Therefore out_msg_pos_next() can assume:
    - if we're in the trail portion of a message, the message data
      pagelist, data, and bio can be ignored; and
    - if there is a page list, there will never be any a bio or page
      array data, and vice-versa.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
This commit is contained in:
Alex Elder 2013-03-06 23:39:39 -06:00 committed by Sage Weil
parent dd236fcb65
commit 7fe1e5e57b
1 changed files with 13 additions and 12 deletions
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25
net/ceph/messenger.c
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@ -931,8 +931,10 @@ static void prepare_message_data(struct ceph_msg *msg,
#endif
msg_pos->data_pos = 0;
/* If there's a trail, initialize its cursor */
/* Initialize data cursors */
if (ceph_msg_has_pagelist(msg))
ceph_msg_data_cursor_init(&msg->l);
if (ceph_msg_has_trail(msg))
ceph_msg_data_cursor_init(&msg->t);
@ -1220,18 +1222,19 @@ static void out_msg_pos_next(struct ceph_connection *con, struct page *page,
{
struct ceph_msg *msg = con->out_msg;
struct ceph_msg_pos *msg_pos = &con->out_msg_pos;
bool need_crc = false;
BUG_ON(!msg);
BUG_ON(!sent);
msg_pos->data_pos += sent;
msg_pos->page_pos += sent;
if (in_trail) {
bool need_crc;
if (in_trail)
need_crc = ceph_msg_data_advance(&msg->t, sent);
BUG_ON(need_crc && sent != len);
}
else if (ceph_msg_has_pagelist(msg))
need_crc = ceph_msg_data_advance(&msg->l, sent);
BUG_ON(need_crc && sent != len);
if (sent < len)
return;
@ -1239,13 +1242,10 @@ static void out_msg_pos_next(struct ceph_connection *con, struct page *page,
msg_pos->page_pos = 0;
msg_pos->page++;
msg_pos->did_page_crc = false;
if (ceph_msg_has_pagelist(msg)) {
list_rotate_left(&msg->l.pagelist->head);
#ifdef CONFIG_BLOCK
} else if (ceph_msg_has_bio(msg)) {
if (ceph_msg_has_bio(msg))
iter_bio_next(&msg->b.bio_iter, &msg->b.bio_seg);
#endif
}
}
static void in_msg_pos_next(struct ceph_connection *con, size_t len,
@ -1340,8 +1340,9 @@ static int write_partial_message_data(struct ceph_connection *con)
} else if (ceph_msg_has_pages(msg)) {
page = msg->p.pages[msg_pos->page];
} else if (ceph_msg_has_pagelist(msg)) {
page = list_first_entry(&msg->l.pagelist->head,
struct page, lru);
use_cursor = true;
page = ceph_msg_data_next(&msg->l, &page_offset,
&length, &last_piece);
#ifdef CONFIG_BLOCK
} else if (ceph_msg_has_bio(msg)) {
struct bio_vec *bv;