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Date: Fri, 20 Jul 2007 16:13:04 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Andrew Morton <akpm@linux-foundation.org>
CC: Badari Pulavarty <pbadari@us.ibm.com>, Bill Irwin <bill.irwin@oracle.com>,
       nacc@us.ibm.com, lkml <linux-kernel@vger.kernel.org>,
       linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH] hugetlbfs read() support
References: <1184376214.15968.9.camel@dyn9047017100.beaverton.ibm.com>	<20070718221950.35bbdb76.akpm@linux-foundation.org>	<1184860309.18188.90.camel@dyn9047017100.beaverton.ibm.com> <20070719095850.6e09b0e8.akpm@linux-foundation.org>
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(sorry if this is a resend... something bad seems to have happened to me)

Andrew Morton wrote:
> On Thu, 19 Jul 2007 08:51:49 -0700 Badari Pulavarty <pbadari@us.ibm.com> wrote:

>>>This code doesn't have all the ghastly tricks which we deploy to handle
>>>concurrent truncate.
>>
>>Do I need to ? Baaahh!!  I don't want to deal with them. 
> 
> 
> Nick, can you think of any serious consequences of a read/truncate race in
> there?  I can't..

As it doesn't allow writes, then I _think_ it should be OK. If you
ever did want to add write(2) support, then you would have transient
zeroes problems.

But I'm not completely sure.. we've had a lot of (and still have
some known and probably unknown) bugs just in that single
generic_mapping_read function, most of which are due to our rabid
aversion to doing any locking whatsoever there.

So why not just hold i_mutex around the whole thing to be safe?

-- 
SUSE Labs, Novell Inc.