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, 26 insertions, 19 deletions

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 8ae59df2e3d1..2c498a2a8268 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -167,27 +167,13 @@ static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
         return sb->s_bdi;
 }
 
-static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
+static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
 {
-        if (bdi->congested_fn)
-                return bdi->congested_fn(bdi->congested_data, bdi_bits);
-        return (bdi->wb.congested->state & bdi_bits);
-}
-
-static inline int bdi_read_congested(struct backing_dev_info *bdi)
-{
-        return bdi_congested(bdi, 1 << WB_sync_congested);
-}
-
-static inline int bdi_write_congested(struct backing_dev_info *bdi)
-{
-        return bdi_congested(bdi, 1 << WB_async_congested);
-}
+        struct backing_dev_info *bdi = wb->bdi;
 
-static inline int bdi_rw_congested(struct backing_dev_info *bdi)
-{
-        return bdi_congested(bdi, (1 << WB_sync_congested) |
-                                  (1 << WB_async_congested));
+        if (bdi->congested_fn)
+                return bdi->congested_fn(bdi->congested_data, cong_bits);
+        return wb->congested->state & cong_bits;
 }
 
 long congestion_wait(int sync, long timeout);
@@ -454,4 +440,25 @@ static inline void wb_blkcg_offline(struct blkcg *blkcg)
 
 #endif  /* CONFIG_CGROUP_WRITEBACK */
 
+static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
+{
+        return wb_congested(&bdi->wb, cong_bits);
+}
+
+static inline int bdi_read_congested(struct backing_dev_info *bdi)
+{
+        return bdi_congested(bdi, 1 << WB_sync_congested);
+}
+
+static inline int bdi_write_congested(struct backing_dev_info *bdi)
+{
+        return bdi_congested(bdi, 1 << WB_async_congested);
+}
+
+static inline int bdi_rw_congested(struct backing_dev_info *bdi)
+{
+        return bdi_congested(bdi, (1 << WB_sync_congested) |
+                                  (1 << WB_async_congested));
+}
+
 #endif  /* _LINUX_BACKING_DEV_H */