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bdi: separate out congested state into a separate struct

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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: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2015-05-22 17:13:35 -04:00 committed by Jens Axboe
parent 8395cd9f81
commit 4aa9c692e0
3 changed files with 18 additions and 5 deletions
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14
include/linux/backing-dev-defs.h
View file

@ -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;

2
include/linux/backing-dev.h
View file

@ -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)

7
mm/backing-dev.c
View file

@ -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);