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Message-ID: <4ed8baf7-7eb9-71e5-58ea-7c73b7e5bb73@fujitsu.com>
Date:   Wed, 30 Mar 2022 18:58:21 +0800
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Subject: Re: [PATCH v11 1/8] dax: Introduce holder for dax_device
To:     Christoph Hellwig <hch@infradead.org>
CC:     Dan Williams <dan.j.williams@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-xfs <linux-xfs@vger.kernel.org>,
        Linux NVDIMM <nvdimm@lists.linux.dev>,
        Linux MM <linux-mm@kvack.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        "Darrick J. Wong" <djwong@kernel.org>, david <david@fromorbit.com>,
        Jane Chu <jane.chu@oracle.com>
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From:   Shiyang Ruan <ruansy.fnst@fujitsu.com>
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在 2022/3/30 18:13, Christoph Hellwig 写道:
> On Wed, Mar 30, 2022 at 06:03:01PM +0800, Shiyang Ruan wrote:
>>
>> Because I am not sure if the offset between each layer is page aligned.  For
>> example, when pmem dirver handles ->memory_failure(), it should subtract its
>> ->data_offset when it calls dax_holder_notify_failure().
> 
> If they aren't, none of the DAX machinery would work.

OK. Got it.

So, use page-based function signature for ->memory_failure():

int (*memory_failure)(struct dev_pagemap *pgmap, unsigned long pfn,
		      unsigned long nr_pfns, int flags);


As the code I pasted before, pmem driver will subtract its 
->data_offset, which is byte-based. And the filesystem who implements 
->notify_failure() will calculate the offset in unit of byte again.

So, leave its function signature byte-based, to avoid repeated conversions.

int (*notify_failure)(struct dax_device *dax_dev, u64 offset,
		      u64 len, int mf_flags);

What do you think?


--
Thanks,
Ruan.