linux-kernel - Re: [-mm patch] UNION

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Date:	Wed, 21 Feb 2007 14:19:44 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Josef Sipek <jsipek@....cs.sunysb.edu>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Adrian Bunk <bunk@...sta.de>, linux-kernel@...r.kernel.org,
	unionfs@...esystems.org
Subject: Re: [-mm patch] UNION_FS must depend on SLAB

On Tue, 20 Feb 2007 10:13:56 -0500
Josef Sipek <jsipek@....cs.sunysb.edu> wrote:

> On Tue, Feb 20, 2007 at 08:37:34AM +0200, Pekka Enberg wrote:
> > On 2/20/07, Adrian Bunk <bunk@...sta.de> wrote:
> > >  CC      fs/unionfs/copyup.o
> > >/home/bunk/linux/kernel-2.6/linux-2.6.20-mm2/fs/unionfs/copyup.c: In 
> > >function 'create_parents_named':
> > >/home/bunk/linux/kernel-2.6/linux-2.6.20-mm2/fs/unionfs/copyup.c:620: 
> > >error: 'malloc_sizes' undeclared (first use in this function)
> > >/home/bunk/linux/kernel-2.6/linux-2.6.20-mm2/fs/unionfs/copyup.c:620: 
> > >error: (Each undeclared identifier is reported only once
> > >/home/bunk/linux/kernel-2.6/linux-2.6.20-mm2/fs/unionfs/copyup.c:620: 
> > >error: for each function it appears in.)
> > >make[3]: *** [fs/unionfs/copyup.o] Error 1
> > 
> > Hmm, why is unionfs playing around with malloc_sizes in the first place? 
> > Jeff?
> 
> The code is in lookup.c:
> 
> if (oldsize) {
> 	int minsize = malloc_sizes[0].cs_size;
> 
> 	if (!newsize || ((oldsize < newsize) && (newsize > minsize))) {
> 		kfree(info->lower_paths);
> 		info->lower_paths = NULL;
> 	}
> }
> 
> That's the only user of malloc_sizes. It is supposed to be an optimization -
> we get the smallest sized piece of memory even if we don't need all of it.
> This way we don't reallocate & memcpy needlessly.
> 

urgh, no, please don't poke around in slab internals like that.

If you want to propose an extension to the slab ABI the please do so and
we'll take a look at it.

I can't say more until I've managed to understand your description, which
might take a while.

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