[PATCH 26/49] writeback: make congestion functions per bdi_writeback

Tejun Heo
2015-04-06T20:16:31Z

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>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
---
include/linux/backing-dev-defs.h | 14 +++++++++++--
include/linux/backing-dev.h | 45 +++++++++++++++++++++++-----------------
mm/backing-dev.c | 22 ++++++++++----------
3 files changed, 49 insertions(+), 32 deletions(-)

diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index a1e9c40..eb38676 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -163,7 +163,17 @@ enum {
BLK_RW_SYNC = 1,
};

-void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
-void set_bdi_congested(struct backing_dev_info *bdi, int sync);
+void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
+void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
+
+static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
+{
+ clear_wb_congested(bdi->wb.congested, sync);
+}
+
+static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
+{
+ set_wb_congested(bdi->wb.congested, sync);
+}

#endif /* __LINUX_BACKING_DEV_DEFS_H */
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 8ae59df..2c498a2 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 */
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 4c9386c..5029c4a 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();

--
2.1.0