From: Matthew Wilcox <willy@linux.intel.com>
Subject: Re: [PATCH v7 08/22] Replace xip_truncate_page with dax_truncate_page
Date: Sun, 13 Apr 2014 15:07:21 -0400
Message-ID: <20140413190721.GA21460@linux.intel.com>
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Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
To: Jan Kara <jack@suse.cz>
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On Wed, Apr 09, 2014 at 11:26:35AM +0200, Jan Kara wrote:
>   I thought about this for a while and classical IO, truncation etc. could
> easily work for blocksize < pagesize. And for mmap() you could just use
> pagecache. Not sure if it's worth the complications though. Anyway we
> should decide whether we don't care about blocksize < PAGE_CACHE_SIZE at
> all, or whether we try to make things which can work reasonably easily
> functional. In that case dax_truncate_page() needs some tweaking because it
> currently assumes blocksize == PAGE_CACHE_SIZE.

I think it actually assumes that blocksize <= PAGE_CACHE_SIZE in that
it doesn't contain a loop to iterate over all blocks.  It wouldn't be
hard to fix but I'll just put in a comment noting what needs to be fixed
... I don't think there's going to be a lot of enthusiasm for adding
support for blocksize != PAGE_SIZE / PAGE_CACHE_SIZE.

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