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Date: Tue, 30 Jun 2015 16:50:41 +0200
From: Jan Kara <jack@...e.cz>
To: Tejun Heo <tj@...nel.org>
Cc: axboe@...nel.dk, linux-kernel@...r.kernel.org, jack@...e.cz,
hch@...radead.org, hannes@...xchg.org,
linux-fsdevel@...r.kernel.org, vgoyal@...hat.com,
lizefan@...wei.com, cgroups@...r.kernel.org, linux-mm@...ck.org,
mhocko@...e.cz, clm@...com, fengguang.wu@...el.com,
david@...morbit.com, gthelen@...gle.com, khlebnikov@...dex-team.ru
Subject: Re: [PATCH 27/51] writeback: make congestion functions per
bdi_writeback
On Fri 22-05-15 17:13:41, Tejun Heo wrote:
> 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.
Looks good to me. You can add:
Reviewed-by: Jan Kara <jack@...e.com>
Honza
>
> v2: Updated for bdi_writeback_congested.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reviewed-by: Jan Kara <jack@...e.cz>
> Cc: Jens Axboe <axboe@...nel.dk>
> ---
> 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();
>
> --
> 2.4.0
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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