From: Harry Yoo <harry.yoo@oracle.com>
To: "Christoph Lameter (Ampere)" <cl@gentwo.org>
Cc: vbabka@suse.cz, rientjes@google.com, akpm@linux-foundation.org,
roman.gushchin@linux.dev, willy@infradead.org,
linux-mm@kvack.org
Subject: Re: [PATCH] mm/slab: fix folio_test_{anon,ksm}() false positive on slabs
Date: Tue, 10 Jun 2025 21:39:09 +0900 [thread overview]
Message-ID: <aEgnbbjPacfb5YGg@hyeyoo> (raw)
In-Reply-To: <3fcbe4a8-dfc6-c708-f765-859d9f191c91@gentwo.org>
On Mon, Jun 09, 2025 at 09:06:04AM -0700, Christoph Lameter (Ampere) wrote:
> On Mon, 9 Jun 2025, Harry Yoo wrote:
>
> > [ field ] [ offset ] [ size ]
> > page->mapping 24 8
> > page->lru 8 16
> >
> > slab->next 16 8
> > slab->slabs 24 4
> >
> > Reorder ->slabs and ->next, so that the layout will be:
> >
> > slab->slabs 16 4
> > slab->next 24 8
> >
> > After reordering, slab->slabs shares its offset with page->lru.prev,
> > which is not a problem. slab->next now shares the offset with
> > page->mapping, but that's fine, as a slab is double-word aligned.
>
> Add comments to document the trickery that is going on here? Otherwise we
> may stumble across this issue again later.
Will add, thanks!
--
Cheers,
Harry / Hyeonggon
prev parent reply other threads:[~2025-06-10 12:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-09 13:27 Harry Yoo
2025-06-09 14:12 ` Harry Yoo
2025-06-09 14:22 ` Vlastimil Babka
2025-06-10 12:38 ` Harry Yoo
2025-06-10 13:03 ` Vlastimil Babka
2025-06-10 13:17 ` Harry Yoo
2025-06-12 12:44 ` David Hildenbrand
2025-06-09 16:06 ` Christoph Lameter (Ampere)
2025-06-10 12:39 ` Harry Yoo [this message]
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