From: Andrew Morton <akpm@linux-foundation.org>
To: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>,
"Liam R. Howlett" <liam@infradead.org>,
David Hildenbrand <david@kernel.org>,
Vlastimil Babka <vbabka@kernel.org>, Jann Horn <jannh@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Mike Kaplinskiy <mike@recall.ai>,
zhaozhengzhuo <zhaozhengzhuo@uniontech.com>
Subject: Re: [PATCH] mm/madvise: swap in CoW'd MAP_PRIVATE-file mappings on MADV_WILLNEED
Date: Sat, 5 Sep 2026 17:17:57 -0700 [thread overview]
Message-ID: <20260905171757.ba8b0f8f0f18ebd04418bfeb@linux-foundation.org> (raw)
In-Reply-To: <aprjOxDy3JCPb2oa@gremlin>
On Fri, 4 Sep 2026 17:01:37 +0100 "Lorenzo Stoakes (ARM)" <ljs@kernel.org> wrote:
> Andrew - could you swap the patch out in-place with below? Thanks!
>
np.
> Currently MADV_WILLNEED treats file-backed and pure anonymous mappings
> entirely separately - using POSIX_FADV_WILLNEED (equivalent of a readahead)
> for the former and a tree walk and swap in to swap cache for the latter.
>
> MAP_PRIVATE-file backed mappings straddle the two and currently get treated
> as if they were purely file-backed, meaning any swapped out private pages
> remain swapped out.
>
> Resolve the issue by explicitly checking for CoW'd MAP_PRIVATE-file backed
> mappings and performing both walks in this case.
>
> Since the logic checks for vma->anon_vma this means un-CoW'd
> MAP_PRIVATE-file backed mappings retain only the single file walk.
>
> Reported-by: Mike Kaplinskiy <mike@recall.ai>
> Closes: https://lore.kernel.org/all/CABeknB_S2XJSHFgnHdgnN0rjzHhH4oQJs_APq9fvxHztQ_pgiA@mail.gmail.com/
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
The failure mode looks pretty obscure, so I'm thinking that no backport
is needed.
next prev parent reply other threads:[~2026-09-06 0:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-04 15:12 Lorenzo Stoakes (ARM)
2026-09-04 15:24 ` Pedro Falcato
2026-09-04 16:01 ` Lorenzo Stoakes (ARM)
2026-09-06 0:17 ` Andrew Morton [this message]
2026-09-07 12:32 ` Lorenzo Stoakes (ARM)
2026-09-07 15:09 ` Vlastimil Babka (SUSE)
2026-09-07 15:27 ` Lorenzo Stoakes (ARM)
2026-09-07 11:51 ` David Hildenbrand (Arm)
2026-09-07 12:33 ` Lorenzo Stoakes (ARM)
2026-09-07 12:39 ` Pedro Falcato
2026-09-07 15:05 ` Vlastimil Babka (SUSE)
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