linux-kernel - Re: [PATCH v2] zram: fix incorrectly stat with failed

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Date:	Wed, 13 Aug 2014 10:31:45 +0200
From:	Jerome Marchand <jmarchan@...hat.com>
To:	Chao Yu <chao2.yu@...sung.com>, minchan@...nel.org
CC:	ngupta@...are.org, linux-kernel@...r.kernel.org,
	"'Sergey Senozhatsky'" <sergey.senozhatsky@...il.com>,
	"'Andrew Morton'" <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] zram: fix incorrectly stat with failed_reads

On 08/13/2014 04:01 AM, Chao Yu wrote:
> Since we allocate a temporary buffer in zram_bvec_read to handle partial page
> operations in this commit 924bd88d703e53d30f393fac6117f8f1bc79aab6 (Staging:
> zram: allow partial page operations), our ->failed_reads value may be incorrect
> as we do not increase its value when failed to allocate the temporary buffer.
> 
> Let's fix this issue and correct the annotation of failed_reads.
> 
>  v2: clean codes of failed_{reads,writes} stat pointed out by Minchan Kim, and
> this cleanup also fix incorrectly stat when fail in zram_decompress_page.
> 
> Signed-off-by: Chao Yu <chao2.yu@...sung.com>

Acked-by: Jerome Marchand <jmarchan@...hat.com>

> ---
>  drivers/block/zram/zram_drv.c | 10 +++++++---
>  drivers/block/zram/zram_drv.h |  2 +-
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index dfa4024..d00831c 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -378,7 +378,6 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
>  	/* Should NEVER happen. Return bio error if it does. */
>  	if (unlikely(ret)) {
>  		pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
> -		atomic64_inc(&zram->stats.failed_reads);
>  		return ret;
>  	}
>  
> @@ -547,8 +546,6 @@ out:
>  		zcomp_strm_release(zram->comp, zstrm);
>  	if (is_partial_io(bvec))
>  		kfree(uncmem);
> -	if (ret)
> -		atomic64_inc(&zram->stats.failed_writes);
>  	return ret;
>  }
>  
> @@ -566,6 +563,13 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
>  		ret = zram_bvec_write(zram, bvec, index, offset);
>  	}
>  
> +	if (unlikely(ret)) {
> +		if (rw == READ)
> +			atomic64_inc(&zram->stats.failed_reads);
> +		else
> +			atomic64_inc(&zram->stats.failed_writes);
> +	}
> +
>  	return ret;
>  }
>  
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index 5b0afde..e0f725c 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -84,7 +84,7 @@ struct zram_stats {
>  	atomic64_t compr_data_size;	/* compressed size of pages stored */
>  	atomic64_t num_reads;	/* failed + successful */
>  	atomic64_t num_writes;	/* --do-- */
> -	atomic64_t failed_reads;	/* should NEVER! happen */
> +	atomic64_t failed_reads;	/* can happen when memory is too low */
>  	atomic64_t failed_writes;	/* can happen when memory is too low */
>  	atomic64_t invalid_io;	/* non-page-aligned I/O requests */
>  	atomic64_t notify_free;	/* no. of swap slot free notifications */
> 



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