linux-kernel - Re: [PATCH] zram: use scnprintf() in attrs show() methods

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Message-ID: <20140310020914.GE14370@bbox>
Date:	Mon, 10 Mar 2014 11:09:14 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] zram: use scnprintf() in attrs show() methods

On Sun, Mar 09, 2014 at 10:27:08PM +0300, Sergey Senozhatsky wrote:
> sysfs.txt documentation lists the following requirements:
> 
>  - The buffer will always be PAGE_SIZE bytes in length. On i386, this
>    is 4096.
> 
>  - show() methods should return the number of bytes printed into the
>    buffer. This is the return value of scnprintf().
> 
>  - show() should always use scnprintf().
> 
> Use scnprintf() in show() functions.
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

Acked-by: Minchan Kim <minchan@...nel.org>

> ---
>  drivers/block/zram/zcomp.c    |  8 +++++---
>  drivers/block/zram/zram_drv.c | 12 ++++++------
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> index 92a83df..ffcaff7 100644
> --- a/drivers/block/zram/zcomp.c
> +++ b/drivers/block/zram/zcomp.c
> @@ -274,12 +274,14 @@ ssize_t zcomp_available_show(const char *comp, char *buf)
>  
>  	while (backends[i]) {
>  		if (sysfs_streq(comp, backends[i]->name))
> -			sz += sprintf(buf + sz, "[%s] ", backends[i]->name);
> +			sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
> +					"[%s] ", backends[i]->name);
>  		else
> -			sz += sprintf(buf + sz, "%s ", backends[i]->name);
> +			sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
> +					"%s ", backends[i]->name);
>  		i++;
>  	}
> -	sz += sprintf(buf + sz, "\n");
> +	sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n");
>  	return sz;
>  }
>  
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 7631ef0..e6ff420 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -47,7 +47,7 @@ static ssize_t zram_attr_##name##_show(struct device *d,		\
>  				struct device_attribute *attr, char *b)	\
>  {									\
>  	struct zram *zram = dev_to_zram(d);				\
> -	return sprintf(b, "%llu\n",					\
> +	return scnprintf(b, PAGE_SIZE, "%llu\n",			\
>  		(u64)atomic64_read(&zram->stats.name));			\
>  }									\
>  static struct device_attribute dev_attr_##name =			\
> @@ -68,7 +68,7 @@ static ssize_t disksize_show(struct device *dev,
>  {
>  	struct zram *zram = dev_to_zram(dev);
>  
> -	return sprintf(buf, "%llu\n", zram->disksize);
> +	return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize);
>  }
>  
>  static ssize_t initstate_show(struct device *dev,
> @@ -81,7 +81,7 @@ static ssize_t initstate_show(struct device *dev,
>  	val = init_done(zram);
>  	up_read(&zram->init_lock);
>  
> -	return sprintf(buf, "%u\n", val);
> +	return scnprintf(buf, PAGE_SIZE, "%u\n", val);
>  }
>  
>  static ssize_t orig_data_size_show(struct device *dev,
> @@ -89,7 +89,7 @@ static ssize_t orig_data_size_show(struct device *dev,
>  {
>  	struct zram *zram = dev_to_zram(dev);
>  
> -	return sprintf(buf, "%llu\n",
> +	return scnprintf(buf, PAGE_SIZE, "%llu\n",
>  		(u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
>  }
>  
> @@ -105,7 +105,7 @@ static ssize_t mem_used_total_show(struct device *dev,
>  		val = zs_get_total_size_bytes(meta->mem_pool);
>  	up_read(&zram->init_lock);
>  
> -	return sprintf(buf, "%llu\n", val);
> +	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
>  }
>  
>  static ssize_t max_comp_streams_show(struct device *dev,
> @@ -118,7 +118,7 @@ static ssize_t max_comp_streams_show(struct device *dev,
>  	val = zram->max_comp_streams;
>  	up_read(&zram->init_lock);
>  
> -	return sprintf(buf, "%d\n", val);
> +	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
>  }
>  
>  static ssize_t max_comp_streams_store(struct device *dev,
> -- 
> 1.9.0.477.g83111a0
> 
> --
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-- 
Kind regards,
Minchan Kim
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