writeback: make congestion functions per bdi_writeback

Currently, all congestion functions take bdi (backing_dev_info) and
always operate on the root wb (bdi->wb) and the congestion state from
the block layer is propagated only for the root blkcg.  This patch
introduces {set|clear}_wb_congested() and wb_congested() which take a
bdi_writeback_congested and bdi_writeback respectively.  The bdi
counteparts are now wrappers invoking the wb based functions on
@bdi->wb.

While converting clear_bdi_congested() to clear_wb_congested(), the
local variable declaration order between @wqh and @bit is swapped for
cosmetic reason.

This patch just adds the new wb based functions.  The following
patches will apply them.

v2: Updated for bdi_writeback_congested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 11 insertions, 11 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 4c9386c98ec1..5029c4ad2f36 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -896,31 +896,31 @@ static wait_queue_head_t congestion_wqh[2] = {
 		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 	};
-static atomic_t nr_bdi_congested[2];
+static atomic_t nr_wb_congested[2];
 
-void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
+void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
 {
-	enum wb_state bit;
 	wait_queue_head_t *wqh = &congestion_wqh[sync];
+	enum wb_state bit;
 
 	bit = sync ? WB_sync_congested : WB_async_congested;
-	if (test_and_clear_bit(bit, &bdi->wb.congested->state))
-		atomic_dec(&nr_bdi_congested[sync]);
+	if (test_and_clear_bit(bit, &congested->state))
+		atomic_dec(&nr_wb_congested[sync]);
 	smp_mb__after_atomic();
 	if (waitqueue_active(wqh))
 		wake_up(wqh);
 }
-EXPORT_SYMBOL(clear_bdi_congested);
+EXPORT_SYMBOL(clear_wb_congested);
 
-void set_bdi_congested(struct backing_dev_info *bdi, int sync)
+void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
 {
 	enum wb_state bit;
 
 	bit = sync ? WB_sync_congested : WB_async_congested;
-	if (!test_and_set_bit(bit, &bdi->wb.congested->state))
-		atomic_inc(&nr_bdi_congested[sync]);
+	if (!test_and_set_bit(bit, &congested->state))
+		atomic_inc(&nr_wb_congested[sync]);
 }
-EXPORT_SYMBOL(set_bdi_congested);
+EXPORT_SYMBOL(set_wb_congested);
 
 /**
  * congestion_wait - wait for a backing_dev to become uncongested
@@ -979,7 +979,7 @@ long wait_iff_congested(struct zone *zone, int sync, long timeout)
 	 * encountered in the current zone, yield if necessary instead
 	 * of sleeping on the congestion queue
 	 */
-	if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
+	if (atomic_read(&nr_wb_congested[sync]) == 0 ||
 	    !test_bit(ZONE_CONGESTED, &zone->flags)) {
 		cond_resched();