linux-kernel - Re: [PATCH 1/2] zram: free meta table in zram_meta

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Date:	Wed, 28 Jan 2015 23:19:17 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Ganesh Mahendran <opensource.ganesh@...il.com>,
	sergey.senozhatsky.work@...il.com
Subject: Re: [PATCH 1/2] zram: free meta table in zram_meta_free

On (01/28/15 17:15), Minchan Kim wrote:
> zram_meta_alloc() and zram_meta_free() are a pair.
> In zram_meta_alloc(), meta table is allocated. So it it better to free
> it in zram_meta_free().
> 
> Signed-off-by: Ganesh Mahendran <opensource.ganesh@...il.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  drivers/block/zram/zram_drv.c | 30 ++++++++++++++----------------
>  drivers/block/zram/zram_drv.h |  1 +
>  2 files changed, 15 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 9250b3f54a8f..a598ada817f0 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -309,6 +309,18 @@ static inline int valid_io_request(struct zram *zram,
>  
>  static void zram_meta_free(struct zram_meta *meta)
>  {
> +	size_t index;


I don't like how we bloat structs w/o any need.
zram keeps ->disksize, so let's use `zram->disksize >> PAGE_SHIFT'
instead of introducing ->num_pages.

	-ss

> +	/* Free all pages that are still in this zram device */
> +	for (index = 0; index < meta->num_pages; index++) {
> +		unsigned long handle = meta->table[index].handle;
> +
> +		if (!handle)
> +			continue;
> +
> +		zs_free(meta->mem_pool, handle);
> +	}
> +
>  	zs_destroy_pool(meta->mem_pool);
>  	vfree(meta->table);
>  	kfree(meta);
> @@ -316,15 +328,14 @@ static void zram_meta_free(struct zram_meta *meta)
>  
>  static struct zram_meta *zram_meta_alloc(int device_id, u64 disksize)
>  {
> -	size_t num_pages;
>  	char pool_name[8];
>  	struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
>  
>  	if (!meta)
>  		return NULL;
>  
> -	num_pages = disksize >> PAGE_SHIFT;
> -	meta->table = vzalloc(num_pages * sizeof(*meta->table));
> +	meta->num_pages = disksize >> PAGE_SHIFT;
> +	meta->table = vzalloc(meta->num_pages * sizeof(*meta->table));
>  	if (!meta->table) {
>  		pr_err("Error allocating zram address table\n");
>  		goto out_error;
> @@ -706,9 +717,6 @@ static void zram_bio_discard(struct zram *zram, u32 index,
>  
>  static void zram_reset_device(struct zram *zram, bool reset_capacity)
>  {
> -	size_t index;
> -	struct zram_meta *meta;
> -
>  	down_write(&zram->init_lock);
>  
>  	zram->limit_pages = 0;
> @@ -718,16 +726,6 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
>  		return;
>  	}
>  
> -	meta = zram->meta;
> -	/* Free all pages that are still in this zram device */
> -	for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
> -		unsigned long handle = meta->table[index].handle;
> -		if (!handle)
> -			continue;
> -
> -		zs_free(meta->mem_pool, handle);
> -	}
> -
>  	zcomp_destroy(zram->comp);
>  	zram->max_comp_streams = 1;
>  
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index b05a816b09ac..e492f6bf11f1 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -96,6 +96,7 @@ struct zram_stats {
>  struct zram_meta {
>  	struct zram_table_entry *table;
>  	struct zs_pool *mem_pool;
> +	size_t num_pages;
>  };
>  
>  struct zram {
> -- 
> 1.9.1
> 
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