linux-kernel - Re: [patch] mm: tiny-shmem fix lor, mmap_sem vs i

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Message-ID: <Pine.LNX.4.64.0809242030090.12147@blonde.site>
Date:	Wed, 24 Sep 2008 20:41:49 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Matt Mackall <mpm@...enic.com>
cc:	David Howells <dhowells@...hat.com>, Nick Piggin <npiggin@...e.de>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	a.p.zijlstra@...llo.nl, linux-kernel@...r.kernel.org,
	Dave Hansen <haveblue@...ibm.com>
Subject: Re: [patch] mm: tiny-shmem fix lor, mmap_sem vs i_mutex

On Wed, 24 Sep 2008, Matt Mackall wrote:
> 
> Is there any reason I shouldn't use truncate() in regular shmem.c if I
> were to unify the two files?

The lock ordering bug is a good reason not to use do_truncate()
in either.  Once Nick's fixup is in mainline, try the unification
based on that, including his #ifndef CONFIG_MMU which is good for
documentation.

But I don't know how ugly all the #ifdef'ing will end up: at the
time you created mm/tiny-shmem.c, we had a stronger embargo on
#ifdefs in *.c than is fashionable today.

If we're hell-bent on #ifdefs throughout mm/shmem.c, I wouldn't
mind scattering some CONFIG_SWAPs in there too, would cut out
lots of overhead when swap unconfigured.  But again, how ugly?

Hugh
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