Re: [RFC PATCH v4 04/17] mm: Add balance_dirty_pages_ratelimited_flags() function

[Jan Kara <jack@suse.cz>]

On Fri 20-05-22 11:36:33, Stefan Roesch wrote:
> This adds the helper function balance_dirty_pages_ratelimited_flags().
> It adds the parameter flags to balance_dirty_pages_ratelimited().
> The flags parameter is passed to balance_dirty_pages(). For async
> buffered writes the flag value will be BDP_ASYNC.
> 
> The new helper function is also used by balance_dirty_pages_ratelimited().
> 
> Signed-off-by: Stefan Roesch <shr@fb.com>

Yeah, as Christoph says perhaps fold this into patch 3. Otherwise the
changes look good to me.

								Honza

> ---
>  include/linux/writeback.h |  3 +++
>  mm/page-writeback.c       | 38 +++++++++++++++++++++++---------------
>  2 files changed, 26 insertions(+), 15 deletions(-)
> 
> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> index a9114c5090e9..1bddad86a4f6 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -377,6 +377,9 @@ void wb_update_bandwidth(struct bdi_writeback *wb);
>  #define BDP_ASYNC 0x0001
>  
>  void balance_dirty_pages_ratelimited(struct address_space *mapping);
> +int balance_dirty_pages_ratelimited_flags(struct address_space *mapping,
> +		unsigned int flags);
> +
>  bool wb_over_bg_thresh(struct bdi_writeback *wb);
>  
>  typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 7a320fd2ad33..3701e813d05f 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1851,28 +1851,18 @@ static DEFINE_PER_CPU(int, bdp_ratelimits);
>   */
>  DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
>  
> -/**
> - * balance_dirty_pages_ratelimited - balance dirty memory state
> - * @mapping: address_space which was dirtied
> - *
> - * Processes which are dirtying memory should call in here once for each page
> - * which was newly dirtied.  The function will periodically check the system's
> - * dirty state and will initiate writeback if needed.
> - *
> - * Once we're over the dirty memory limit we decrease the ratelimiting
> - * by a lot, to prevent individual processes from overshooting the limit
> - * by (ratelimit_pages) each.
> - */
> -void balance_dirty_pages_ratelimited(struct address_space *mapping)
> +int balance_dirty_pages_ratelimited_flags(struct address_space *mapping,
> +					unsigned int flags)
>  {
>  	struct inode *inode = mapping->host;
>  	struct backing_dev_info *bdi = inode_to_bdi(inode);
>  	struct bdi_writeback *wb = NULL;
>  	int ratelimit;
> +	int ret = 0;
>  	int *p;
>  
>  	if (!(bdi->capabilities & BDI_CAP_WRITEBACK))
> -		return;
> +		return ret;
>  
>  	if (inode_cgwb_enabled(inode))
>  		wb = wb_get_create_current(bdi, GFP_KERNEL);
> @@ -1912,9 +1902,27 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
>  	preempt_enable();
>  
>  	if (unlikely(current->nr_dirtied >= ratelimit))
> -		balance_dirty_pages(wb, current->nr_dirtied, 0);
> +		balance_dirty_pages(wb, current->nr_dirtied, flags);
>  
>  	wb_put(wb);
> +	return ret;
> +}
> +
> +/**
> + * balance_dirty_pages_ratelimited - balance dirty memory state
> + * @mapping: address_space which was dirtied
> + *
> + * Processes which are dirtying memory should call in here once for each page
> + * which was newly dirtied.  The function will periodically check the system's
> + * dirty state and will initiate writeback if needed.
> + *
> + * Once we're over the dirty memory limit we decrease the ratelimiting
> + * by a lot, to prevent individual processes from overshooting the limit
> + * by (ratelimit_pages) each.
> + */
> +void balance_dirty_pages_ratelimited(struct address_space *mapping)
> +{
> +	balance_dirty_pages_ratelimited_flags(mapping, 0);
>  }
>  EXPORT_SYMBOL(balance_dirty_pages_ratelimited);
>  
> -- 
> 2.30.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR