From: Christoph Lameter <cl@gentwo.org>
To: Namhyung Kim <namhyung@gmail.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>,
Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next] slub: set PG_slab on all of slab pages
Date: Thu, 1 Mar 2012 09:03:16 -0600 (CST) [thread overview]
Message-ID: <alpine.DEB.2.00.1203010901020.5004@router.home> (raw)
In-Reply-To: <1330587031.1762.46.camel@leonhard>
On Thu, 1 Mar 2012, Namhyung Kim wrote:
> > You cannot free a tail page of a compound higher order page independently.
> > You must free the whole compound.
> >
>
> I meant freeing a *slab object* resides in a compound page using buddy
> system API (e.g. free_pages). I know it's definitely a programming
> error. However there's no safety net to protect and/or warn such a
> misbehavior AFAICS - except for head page which has PG_slab set - when
> it happened by any chance.
?? One generally passed a struct page pointer to the page allocator. Slab
allocator takes pointers to object. The calls that take a pointer to an
object must have a page aligned value.
> Without it, it might be possible to free part of tail pages silently,
> and cause unexpected not-so-funny results some time later. It should be
> hard to find out.
Ok then fix the page allocator to BUG() on tail pages. That is an issue
with the page allocator not the slab allocator.
Adding PG_tail to the flags checked on free should do the trick (at least
for 64 bit).
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next prev parent reply other threads:[~2012-03-01 15:03 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-29 8:54 Namhyung Kim
2012-02-29 15:24 ` Christoph Lameter
2012-03-01 7:30 ` Namhyung Kim
2012-03-01 15:03 ` Christoph Lameter [this message]
2012-03-02 7:12 ` Namhyung Kim
2012-03-02 16:13 ` Christoph Lameter
2012-03-04 10:34 ` Minchan Kim
2012-03-05 8:42 ` Namhyung Kim
2012-03-05 10:59 ` Minchan Kim
2012-03-05 14:48 ` Christoph Lameter
2012-03-06 1:16 ` Minchan Kim
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