linux-kernel - Re: [PATCH] zram: clean up valid_io

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Date:	Thu, 18 Aug 2016 12:25:11 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Shawn Lin <shawn.lin@...k-chips.com>
Cc:	Minchan Kim <minchan@...nel.org>, Nitin Gupta <ngupta@...are.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] zram: clean up valid_io_request

Hi,

On (08/18/16 11:08), Shawn Lin wrote:
[..]
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 04365b1..1094e95 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -120,15 +120,15 @@ static inline bool valid_io_request(struct zram *zram,
>  	u64 end, bound;
>  
>  	/* unaligned request */
> -	if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
> +	if (unlikely(!IS_ALIGNED(start, ZRAM_SECTOR_PER_LOGICAL_BLOCK)))
>  		return false;
> -	if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
> +	if (unlikely(!IS_ALIGNED(size, ZRAM_LOGICAL_BLOCK_SIZE)))
>  		return false;

ok.

>  	end = start + (size >> SECTOR_SHIFT);
>  	bound = zram->disksize >> SECTOR_SHIFT;
>  	/* out of range range */
> -	if (unlikely(start >= bound || end > bound || start > end))
> +	if (unlikely(start >= bound || end > bound))
>  		return false;

why did you drop `start > end'? what if `start + (size >> SECTOR_SHIFT)'
overflows and `start' becomes greater than `end'?

	-ss