Commit 4aa9c692 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

bdi: separate out congested state into a separate struct 



Currently, a wb's (bdi_writeback) congestion state is carried in its
->state field; however, cgroup writeback support will require multiple
wb's sharing the same congestion state.  This patch separates out
congestion state into its own struct - struct bdi_writeback_congested.
A new field wb field, wb_congested, points to its associated congested
struct.  The default wb, bdi->wb, always points to bdi->wb_congested.

While this patch adds a layer of indirection, it doesn't introduce any
behavior changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 8395cd9f

include/linux/backing-dev-defs.h

+12 −2
Original line number Diff line number Diff line
@@ -16,12 +16,15 @@ struct dentry; 
 * Bits in bdi_writeback.state

 */

enum wb_state {

	WB_async_congested,	/* The async (write) queue is getting full */

	WB_sync_congested,	/* The sync queue is getting full */

	WB_registered,		/* bdi_register() was done */

	WB_writeback_running,	/* Writeback is in progress */

};



enum wb_congested_state {

	WB_async_congested,	/* The async (write) queue is getting full */

	WB_sync_congested,	/* The sync queue is getting full */

};



typedef int (congested_fn)(void *, int);



enum wb_stat_item {
@@ -34,6 +37,10 @@ enum wb_stat_item { 


#define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))



struct bdi_writeback_congested {

	unsigned long state;		/* WB_[a]sync_congested flags */

};



struct bdi_writeback {

	struct backing_dev_info *bdi;	/* our parent bdi */
@@ -48,6 +55,8 @@ struct bdi_writeback { 


	struct percpu_counter stat[NR_WB_STAT_ITEMS];



	struct bdi_writeback_congested *congested;



	unsigned long bw_time_stamp;	/* last time write bw is updated */

	unsigned long dirtied_stamp;

	unsigned long written_stamp;	/* pages written at bw_time_stamp */
@@ -84,6 +93,7 @@ struct backing_dev_info { 
	unsigned int max_ratio, max_prop_frac;



	struct bdi_writeback wb;  /* default writeback info for this bdi */

	struct bdi_writeback_congested wb_congested;



	struct device *dev;

include/linux/backing-dev.h

+1 −1
Original line number Diff line number Diff line
@@ -167,7 +167,7 @@ static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits) 
{

	if (bdi->congested_fn)

		return bdi->congested_fn(bdi->congested_data, bdi_bits);

	return (bdi->wb.state & bdi_bits);

	return (bdi->wb.congested->state & bdi_bits);

}



static inline int bdi_read_congested(struct backing_dev_info *bdi)

mm/backing-dev.c

+5 −2
Original line number Diff line number Diff line
@@ -383,6 +383,9 @@ int bdi_init(struct backing_dev_info *bdi) 
	if (err)

		return err;



	bdi->wb_congested.state = 0;

	bdi->wb.congested = &bdi->wb_congested;



	return 0;

}

EXPORT_SYMBOL(bdi_init);
@@ -504,7 +507,7 @@ void clear_bdi_congested(struct backing_dev_info *bdi, int sync) 
	wait_queue_head_t *wqh = &congestion_wqh[sync];



	bit = sync ? WB_sync_congested : WB_async_congested;

	if (test_and_clear_bit(bit, &bdi->wb.state))

	if (test_and_clear_bit(bit, &bdi->wb.congested->state))

		atomic_dec(&nr_bdi_congested[sync]);

	smp_mb__after_atomic();

	if (waitqueue_active(wqh))
@@ -517,7 +520,7 @@ void set_bdi_congested(struct backing_dev_info *bdi, int sync) 
	enum wb_state bit;



	bit = sync ? WB_sync_congested : WB_async_congested;

	if (!test_and_set_bit(bit, &bdi->wb.state))

	if (!test_and_set_bit(bit, &bdi->wb.congested->state))

		atomic_inc(&nr_bdi_congested[sync]);

}

EXPORT_SYMBOL(set_bdi_congested);

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