linux-kernel - Re: [PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap

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Message-ID: <9fb0c82f-b2ae-82e3-62df-f0a473ed6395@fujitsu.com>
Date:   Thu, 16 Sep 2021 16:49:19 +0800
From:   Shiyang Ruan <ruansy.fnst@...itsu.com>
To:     Christoph Hellwig <hch@....de>
CC:     <djwong@...nel.org>, <linux-xfs@...r.kernel.org>,
        <dan.j.williams@...el.com>, <david@...morbit.com>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <nvdimm@...ts.linux.dev>, <rgoldwyn@...e.de>,
        <viro@...iv.linux.org.uk>, <willy@...radead.org>,
        Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: Re: [PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero



On 2021/9/16 14:16, Christoph Hellwig wrote:
> On Wed, Sep 15, 2021 at 06:44:58PM +0800, Shiyang Ruan wrote:
>> +	rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL);
>> +	if (rc < 0)
>> +		goto out;
>> +	memset(kaddr + offset, 0, size);
>> +	if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
> 
> Should we also check that ->dax_dev for iomap and srcmap are different
> first to deal with case of file system with multiple devices?

I have not thought of this case.  Isn't it possible to CoW between 
different devices?


--
Thanks,
Ruan

> 
> Otherwise looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@....de>
>