linux-kernel - Re: [PATCH] mm/sl[aou]b: make kfree() aware of error pointers

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Date:	Wed, 10 Sep 2014 08:59:33 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Jiri Kosina <jkosina@...e.cz>, Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH] mm/sl[aou]b: make kfree() aware of error pointers

On Tue, 9 Sep 2014, Andrew Morton wrote:

> >
> > -	if (unlikely(ZERO_OR_NULL_PTR(objp)))
> > +	if (unlikely(ZERO_OR_NULL_PTR(objp) || IS_ERR(objp)))
> >  		return;
>
> kfree() is quite a hot path to which this will add overhead.  And we
> have (as far as we know) no code which will actually use this at
> present.

We could come up with a macro that does both. Basically if objp < 4086 or
so (signed comparison) then just return.

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