linux-kernel - Re: [PATCH -next] zram: fix compr_data

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Date:   Fri, 11 Aug 2017 10:35:53 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Yisheng Xie <xieyisheng1@...wei.com>
Cc:     akpm@...ux-foundation.org, minchan@...nel.org, ngupta@...are.org,
        sergey.senozhatsky.work@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] zram: fix compr_data_size stat

On (08/11/17 09:10), Yisheng Xie wrote:
> The compr_data_size is a stat for compressed size of pages stored, which
> should add comp_len when we compresse a page.
> 
> Meanwhile fix typos in comment:
> * ZRAM_SAME means page consists the same element not the entirely zero page
> * read_from_bdev_async() return 1 to avoid call page_endio() in zram_rw_page()
> 
> Signed-off-by: Yisheng Xie <xieyisheng1@...wei.com>

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

> ---
>  drivers/block/zram/zram_drv.c | 3 ++-
>  drivers/block/zram/zram_drv.h | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index e27daca..b2b75b1 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -455,7 +455,7 @@ void zram_page_end_io(struct bio *bio)
>  }
>  
>  /*
> - * Returns 0 if the submission is successful.
> + * Returns 1 if the submission is successful.
>   */
>  static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
>  			unsigned long entry, struct bio *parent)

ok.


> @@ -1073,6 +1073,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
>  	}  else {
>  		zram_set_handle(zram, index, handle);
>  		zram_set_obj_size(zram, index, comp_len);
> +		atomic64_add(comp_len, &zram->stats.compr_data_size);

hm. looks like nothing increments ->compr_data_size as of now... we only
decrement it. so it's possible to have something like

# cat /sys/block/zram0/mm_stat 

163594240 18446744073709549720 80388096        0 80388096    15927        0

oops... good catch.


>  	}
>  	zram_slot_unlock(zram, index);
>  
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index 5573dc2..31762db 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -60,7 +60,7 @@
>  
>  /* Flags for zram pages (table[page_no].value) */
>  enum zram_pageflags {
> -	/* Page consists entirely of zeros */
> +	/* Page consists the same element */
>  	ZRAM_SAME = ZRAM_FLAG_SHIFT,
>  	ZRAM_ACCESS,	/* page is now accessed */
>  	ZRAM_WB,	/* page is stored on backing_device */

ok.

	-ss