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Date: Fri, 20 Jul 2007 14:29:11 +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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Andrew Morton wrote:
> On Thu, 19 Jul 2007 08:51:49 -0700 Badari Pulavarty <pbadari@us.ibm.com> wrote:
> 
> 
>>>>+		}
>>>>+
>>>>+		offset += ret;
>>>>+		retval += ret;
>>>>+		len -= ret;
>>>>+		index += offset >> HPAGE_SHIFT;
>>>>+		offset &= ~HPAGE_MASK;
>>>>+
>>>>+		page_cache_release(page);
>>>>+		if (ret == nr && len)
>>>>+			continue;
>>>>+		goto out;
>>>>+	}
>>>>+out:
>>>>+	return retval;
>>>>+}
>>>
>>>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 why not just hold i_mutex around the whole thing just to be safe?

-- 
SUSE Labs, Novell Inc.