linux-kernel - Re: [PATCH] hugetlbfs read() support

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Message-ID: <46A03A17.8090708@yahoo.com.au>
Date:	Fri, 20 Jul 2007 14:29:11 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Badari Pulavarty <pbadari@...ibm.com>,
	Bill Irwin <bill.irwin@...cle.com>, nacc@...ibm.com,
	lkml <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] hugetlbfs read() support

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