[PATCH 28/49] writeback, blkcg: propagate non-root blkcg congestion state

Tejun Heo
2015-04-06T20:00:18Z

Now that bdi layer can handle per-blkcg bdi_writeback_congested state,
blk_{set|clear}_congested() can propagate non-root blkcg congestion
state to them.

This can be easily achieved by disabling the root_rl tests in
blk_{set|clear}_congested(). Note that we still need those tests when
!CONFIG_CGROUP_WRITEBACK as otherwise we'll end up flipping root blkcg
wb's congestion state for events happening on other blkcgs.

v2: Updated for bdi_writeback_congested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-core.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index cad26e3..95488fb 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -65,23 +65,26 @@ static struct workqueue_struct *kblockd_workqueue;

static void blk_clear_congested(struct request_list *rl, int sync)
{
- if (rl != &rl->q->root_rl)
- return;
#ifdef CONFIG_CGROUP_WRITEBACK
clear_wb_congested(rl->blkg->wb_congested, sync);
#else
- clear_wb_congested(rl->q->backing_dev_info.wb.congested, sync);
+ /*
+ * If !CGROUP_WRITEBACK, all blkg's map to bdi->wb and we shouldn't
+ * flip its congestion state for events on other blkcgs.
+ */
+ if (rl == &rl->q->root_rl)
+ clear_wb_congested(rl->q->backing_dev_info.wb.congested, sync);
#endif
}

static void blk_set_congested(struct request_list *rl, int sync)
{
- if (rl != &rl->q->root_rl)
- return;
#ifdef CONFIG_CGROUP_WRITEBACK
set_wb_congested(rl->blkg->wb_congested, sync);
#else
- set_wb_congested(rl->q->backing_dev_info.wb.congested, sync);
+ /* see blk_clear_congested() */
+ if (rl == &rl->q->root_rl)
+ set_wb_congested(rl->q->backing_dev_info.wb.congested, sync);
#endif
}

--
2.1.0