Re: [PATCH 20/49] bdi: separate out congested state into a separate struct

Jan Kara
2015-04-21T14:36:56Z

On Mon 06-04-15 15:58:09, Tejun Heo wrote:
> 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>
OK. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> include/linux/backing-dev-defs.h | 14 ++++++++++++--
> include/linux/backing-dev.h | 2 +-
> mm/backing-dev.c | 7 +++++--
> 3 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
> index aa18c4b..9e9eafa 100644
> --- a/include/linux/backing-dev-defs.h
> +++ b/include/linux/backing-dev-defs.h
> @@ -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;
>
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index 7857820..bfdaa18 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -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)
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index 805b287..5ec7658 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -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);
> --
> 2.1.0
>
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR