From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751200AbdBCPt0 (ORCPT <rfc822;w@1wt.eu>);
        Fri, 3 Feb 2017 10:49:26 -0500
Received: from bombadil.infradead.org ([65.50.211.133]:52231 "EHLO
        bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751131AbdBCPtV (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 3 Feb 2017 10:49:21 -0500
Date: Fri, 3 Feb 2017 07:33:50 -0800
From: Matthew Wilcox <willy@infradead.org>
To: zhouxianrong@huawei.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        akpm@linux-foundation.org, sergey.senozhatsky@gmail.com,
        minchan@kernel.org, iamjoonsoo.kim@lge.com, ngupta@vflare.org,
        Mi.Sophia.Wang@huawei.com, zhouxiyu@huawei.com, weidu.du@huawei.com,
        zhangshiming5@huawei.com, won.ho.park@huawei.com
Subject: Re: [PATCH] mm: extend zero pages to same element pages for zram
Message-ID: <20170203153350.GC2267@bombadil.infradead.org>
References: <1483692145-75357-1-git-send-email-zhouxianrong@huawei.com>
 <1486111347-112972-1-git-send-email-zhouxianrong@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1486111347-112972-1-git-send-email-zhouxianrong@huawei.com>
User-Agent: Mutt/1.7.1 (2016-10-04)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Feb 03, 2017 at 04:42:27PM +0800, zhouxianrong@huawei.com wrote:
> +static inline void zram_fill_page_partial(char *ptr, unsigned int size,
> +		unsigned long value)
> +{
> +	int i;
> +	unsigned long *page;
> +
> +	if (likely(value == 0)) {
> +		memset(ptr, 0, size);
> +		return;
> +	}
> +
> +	i = ((unsigned long)ptr) % sizeof(*page);
> +	if (i) {
> +		while (i < sizeof(*page)) {
> +			*ptr++ = (value >> (i * 8)) & 0xff;
> +			--size;
> +			++i;
> +		}
> +	}
> +
> +	for (i = size / sizeof(*page); i > 0; --i) {
> +		page = (unsigned long *)ptr;
> +		*page = value;
> +		ptr += sizeof(*page);
> +		size -= sizeof(*page);
> +	}
> +
> +	for (i = 0; i < size; ++i)
> +		*ptr++ = (value >> (i * 8)) & 0xff;
> +}

You're assuming little-endian here.  I think you need to do a
cpu_to_le() here, but I don't think we have a cpu_to_leul, only
cpu_to_le64/cpu_to_le32.  So you may have some work to do ...