block: simplify force plug flush code a little bit
Cleaning up the code a little bit. attempt_plug_merge() traverses the plug
list anyway, we can do the request counting there, so stack size is reduced
a little bit.
The motivation here is I suspect if we should count the requests for each
queue (task could handle multiple disks in the meantime), but my test doesn't
show it's worthy doing. If somebody proves we should do it, below change
will make that more easier.
Signed-off-by: Shaohua Li <shli@kernel.org>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/blk-core.c b/block/blk-core.c
index 67dba69..b2ed78a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1167,7 +1167,7 @@
* true if merge was successful, otherwise false.
*/
static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q,
- struct bio *bio)
+ struct bio *bio, unsigned int *request_count)
{
struct blk_plug *plug;
struct request *rq;
@@ -1176,10 +1176,13 @@
plug = tsk->plug;
if (!plug)
goto out;
+ *request_count = 0;
list_for_each_entry_reverse(rq, &plug->list, queuelist) {
int el_ret;
+ (*request_count)++;
+
if (rq->q != q)
continue;
@@ -1219,6 +1222,7 @@
struct blk_plug *plug;
int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
struct request *req;
+ unsigned int request_count = 0;
/*
* low level driver can indicate that it wants pages above a
@@ -1237,7 +1241,7 @@
* Check if we can merge with the plugged list before grabbing
* any locks.
*/
- if (attempt_plug_merge(current, q, bio))
+ if (attempt_plug_merge(current, q, bio, &request_count))
goto out;
spin_lock_irq(q->queue_lock);
@@ -1302,9 +1306,8 @@
if (__rq->q != q)
plug->should_sort = 1;
}
- if (plug->count >= BLK_MAX_REQUEST_COUNT)
+ if (request_count >= BLK_MAX_REQUEST_COUNT)
blk_flush_plug_list(plug, false);
- plug->count++;
list_add_tail(&req->queuelist, &plug->list);
drive_stat_acct(req, 1);
} else {
@@ -2634,7 +2637,6 @@
INIT_LIST_HEAD(&plug->list);
INIT_LIST_HEAD(&plug->cb_list);
plug->should_sort = 0;
- plug->count = 0;
/*
* If this is a nested plug, don't actually assign it. It will be
@@ -2718,7 +2720,6 @@
return;
list_splice_init(&plug->list, &list);
- plug->count = 0;
if (plug->should_sort) {
list_sort(NULL, &list, plug_rq_cmp);