writeback: move backing_dev_info->state into bdi_writeback

Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear.  For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi.  To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.

This patch moves bdi->state into wb.

* enum bdi_state is renamed to wb_state and the prefix of all enums is
  changed from BDI_ to WB_.

* Explicit zeroing of bdi->state is removed without adding zeoring of
  wb->state as the whole data structure is zeroed on init anyway.

* As there's still only one bdi_writeback per backing_dev_info, all
  uses of bdi->state are mechanically replaced with bdi->wb.state
  introducing no behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: drbd-dev@lists.linbit.com
Cc: Neil Brown <neilb@suse.de>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 9157a29c8dbf..f80f1af61ce7 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -745,7 +745,7 @@ static int raid1_congested(struct mddev *mddev, int bits)
         struct r1conf *conf = mddev->private;
         int i, ret = 0;
 
-        if ((bits & (1 << BDI_async_congested)) &&
+        if ((bits & (1 << WB_async_congested)) &&
             conf->pending_count >= max_queued_requests)
                 return 1;
 
@@ -760,7 +760,7 @@ static int raid1_congested(struct mddev *mddev, int bits)
                         /* Note the '|| 1' - when read_balance prefers
                          * non-congested targets, it can be removed
                          */
-                        if ((bits & (1<<BDI_async_congested)) || 1)
+                        if ((bits & (1 << WB_async_congested)) || 1)
                                 ret |= bdi_congested(&q->backing_dev_info, bits);
                         else
                                 ret &= bdi_congested(&q->backing_dev_info, bits);