Re: [PATCH v2] mm/zswap: Check all pool pages instead of one pool pages

[Minchan Kim <minchan@kernel.org>]

Hello Cai,

On Mon, Jan 20, 2014 at 03:50:18PM +0800, Cai Liu wrote:
> zswap can support multiple swapfiles. So we need to check
> all zbud pool pages in zswap.
> 
> Version 2:
>   * add *total_zbud_pages* in zbud to record all the pages in pools
>   * move the updating of pool pages statistics to
>     alloc_zbud_page/free_zbud_page to hide the details
> 
> Signed-off-by: Cai Liu <cai.liu@samsung.com>
> ---
>  include/linux/zbud.h |    2 +-
>  mm/zbud.c            |   44 ++++++++++++++++++++++++++++++++------------
>  mm/zswap.c           |    4 ++--
>  3 files changed, 35 insertions(+), 15 deletions(-)
> 
> diff --git a/include/linux/zbud.h b/include/linux/zbud.h
> index 2571a5c..1dbc13e 100644
> --- a/include/linux/zbud.h
> +++ b/include/linux/zbud.h
> @@ -17,6 +17,6 @@ void zbud_free(struct zbud_pool *pool, unsigned long handle);
>  int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries);
>  void *zbud_map(struct zbud_pool *pool, unsigned long handle);
>  void zbud_unmap(struct zbud_pool *pool, unsigned long handle);
> -u64 zbud_get_pool_size(struct zbud_pool *pool);
> +u64 zbud_get_pool_size(void);
>  
>  #endif /* _ZBUD_H_ */
> diff --git a/mm/zbud.c b/mm/zbud.c
> index 9451361..711aaf4 100644
> --- a/mm/zbud.c
> +++ b/mm/zbud.c
> @@ -52,6 +52,13 @@
>  #include <linux/spinlock.h>
>  #include <linux/zbud.h>
>  
> +/*********************************
> +* statistics
> +**********************************/
> +
> +/* zbud pages in all pools */
> +static u64 total_zbud_pages;
> +
>  /*****************
>   * Structures
>  *****************/
> @@ -142,10 +149,28 @@ static struct zbud_header *init_zbud_page(struct page *page)
>  	return zhdr;
>  }
>  
> +static struct page *alloc_zbud_page(struct zbud_pool *pool, gfp_t gfp)
> +{
> +	struct page *page;
> +
> +	page = alloc_page(gfp);
> +
> +	if (page) {
> +		pool->pages_nr++;
> +		total_zbud_pages++;

Who protect race?

> +	}
> +
> +	return page;
> +}
> +
> +
>  /* Resets the struct page fields and frees the page */
> -static void free_zbud_page(struct zbud_header *zhdr)
> +static void free_zbud_page(struct zbud_pool *pool, struct zbud_header *zhdr)
>  {
>  	__free_page(virt_to_page(zhdr));
> +
> +	pool->pages_nr--;
> +	total_zbud_pages--;
>  }
>  
>  /*
> @@ -279,11 +304,10 @@ int zbud_alloc(struct zbud_pool *pool, int size, gfp_t gfp,
>  
>  	/* Couldn't find unbuddied zbud page, create new one */
>  	spin_unlock(&pool->lock);
> -	page = alloc_page(gfp);
> +	page = alloc_zbud_page(pool, gfp);
>  	if (!page)
>  		return -ENOMEM;
>  	spin_lock(&pool->lock);
> -	pool->pages_nr++;
>  	zhdr = init_zbud_page(page);
>  	bud = FIRST;
>  
> @@ -349,8 +373,7 @@ void zbud_free(struct zbud_pool *pool, unsigned long handle)
>  	if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
>  		/* zbud page is empty, free */
>  		list_del(&zhdr->lru);
> -		free_zbud_page(zhdr);
> -		pool->pages_nr--;
> +		free_zbud_page(pool, zhdr);
>  	} else {
>  		/* Add to unbuddied list */
>  		freechunks = num_free_chunks(zhdr);
> @@ -447,8 +470,7 @@ next:
>  			 * Both buddies are now free, free the zbud page and
>  			 * return success.
>  			 */
> -			free_zbud_page(zhdr);
> -			pool->pages_nr--;
> +			free_zbud_page(pool, zhdr);
>  			spin_unlock(&pool->lock);
>  			return 0;
>  		} else if (zhdr->first_chunks == 0 ||
> @@ -496,14 +518,12 @@ void zbud_unmap(struct zbud_pool *pool, unsigned long handle)
>  
>  /**
>   * zbud_get_pool_size() - gets the zbud pool size in pages
> - * @pool:	pool whose size is being queried
>   *
> - * Returns: size in pages of the given pool.  The pool lock need not be
> - * taken to access pages_nr.
> + * Returns: size in pages of all the zbud pools.
>   */
> -u64 zbud_get_pool_size(struct zbud_pool *pool)
> +u64 zbud_get_pool_size(void)
>  {
> -	return pool->pages_nr;
> +	return total_zbud_pages;
>  }
>  
>  static int __init init_zbud(void)
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 5a63f78..ef44d9d 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -291,7 +291,7 @@ static void zswap_free_entry(struct zswap_tree *tree,
>  	zbud_free(tree->pool, entry->handle);
>  	zswap_entry_cache_free(entry);
>  	atomic_dec(&zswap_stored_pages);
> -	zswap_pool_pages = zbud_get_pool_size(tree->pool);
> +	zswap_pool_pages = zbud_get_pool_size();
>  }
>  
>  /* caller must hold the tree lock */
> @@ -716,7 +716,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
>  
>  	/* update stats */
>  	atomic_inc(&zswap_stored_pages);
> -	zswap_pool_pages = zbud_get_pool_size(tree->pool);
> +	zswap_pool_pages = zbud_get_pool_size();
>  
>  	return 0;
>  
> -- 
> 1.7.10.4
> 
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-- 
Kind regards,
Minchan Kim

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