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

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Date:	Fri, 20 Jul 2007 14:47:31 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Nishanth Aravamudan <nacc@...ibm.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Badari Pulavarty <pbadari@...ibm.com>,
	Bill Irwin <bill.irwin@...cle.com>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] hugetlbfs read() support

Nishanth Aravamudan wrote:
> On 19.07.2007 [09:58:50 -0700], 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..
>>
>>
>>>All I want is a simple read() to get my oprofile working.  Please
>>>advise.
>>
>>Did you consider changing oprofile userspace to read the executable
>>with mmap?
> 
> 
> It's not actually oprofile's code, though, it's libbfd (used by
> oprofile). And it works fine (presumably) for other binaries.

So... what's the problem with changing it? The fact that it is a
library doesn't really make a difference except that you'll also
help everyone else who links with it.

It won't break backwards compatibility, and it will work on older
kernels...

-- 
SUSE Labs, Novell Inc.
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