block: avoid unnecessary plug list flush

get_request_wait() could sleep and flush the plug list.  If the list is
already flushed, don't flush again.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Shaohua Li 2011-11-16 09:21:50 +01:00 committed by Jens Axboe
parent 0007a4c90a
commit 3540d5e89b

View File

@ -1379,15 +1379,17 @@ get_rq:
*/
if (list_empty(&plug->list))
trace_block_plug(q);
else if (!plug->should_sort) {
struct request *__rq;
else {
if (!plug->should_sort) {
struct request *__rq;
__rq = list_entry_rq(plug->list.prev);
if (__rq->q != q)
plug->should_sort = 1;
__rq = list_entry_rq(plug->list.prev);
if (__rq->q != q)
plug->should_sort = 1;
}
if (request_count >= BLK_MAX_REQUEST_COUNT)
blk_flush_plug_list(plug, false);
}
if (request_count >= BLK_MAX_REQUEST_COUNT)
blk_flush_plug_list(plug, false);
list_add_tail(&req->queuelist, &plug->list);
drive_stat_acct(req, 1);
} else {