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Message-ID: <50077819.5040406@oracle.com>
Date: Thu, 19 Jul 2012 10:59:37 +0800
From: Jeff Liu <jeff.liu@oracle.com>
MIME-Version: 1.0
Subject: Re: [PATCH] xfs: Add readpage() check up for mmap file at
	xfs_file_mmap()
References: <5006CC80.3070208@oracle.com>
	<20120718151148.GA17374@infradead.org>
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To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com

On 07/18/2012 11:11 PM, Christoph Hellwig wrote:

> On Wed, Jul 18, 2012 at 10:47:28PM +0800, Jeff Liu wrote:
>> Hello,
>>
>> When studying XFS code, I found xfs_file_mmap() does not check whether a specific file has readpage() or not.
>> Actually, I have no idea of which kind of file does not supply page reading function, but Btrfs/Ext4
>> as well as generic_file_mmap() all do this check at first, do we also need a defense here?
> 
> It's not needed. In generic_file_mmap it might make a little sense as
> any filesystem could use it, but even there's it's questionable because
> ->readpage is the only way to actually supposed mmap when using
> generic_file_mmap.

Now I got it, thanks for the teaching.

Thanks,
-Jeff

> 
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