From: sashiko-bot@kernel.org
To: "Pratyush Yadav" <pratyush@kernel.org>,
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Cc: kexec@lists.infradead.org
Subject: Re: [PATCH 1/3] mm/memfd_luo: don't use memfd_pin_folios()
Date: Wed, 28 Oct 2026 17:31:17 +0000 [thread overview]
Message-ID: <sashiko-outbox-188235@kernel.org> (raw)
In-Reply-To: <20261027173031.763213-2-pratyush@kernel.org>
> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
>
> memfd_luo takes a snapshot of the folios in the file's mapping. To make
> sure the snapshot does not go out of sync, it pins the folios in the
> file via memfd_pin_folios(). The pinning also migrates the folios out of
> MIGRATE_MOVABLE to make sure doesn't land in KHO boot memory or in a CMA
> region.
>
> memfd_pin_folios() does not lock the folios. So it can race with
> shmem_writeout(). A folio returned by memfd_pin_folios() might already
> be in swap cache. This happens to work but is fragile. memfd_luo looks
> at folio flags and index on a folio that isn't in the memfd's page
> cache.
>
> In addition, memfd_pin_folios() needs the caller to allocate an array of
> [ ... ]
> | THP, 32 GiB | 4.83 ms | 5.21 ms | +8% |
> | sparse, 32 GiB | 8695 ms | 7269 ms | -16% |
> |------------------+----------+------------+-------|
>
> Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261027173031.763213-1-pratyush@kernel.org?part=1
next prev parent reply other threads:[~2026-10-28 17:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-27 17:30 [PATCH 0/3] mm: allow freezing mappings Pratyush Yadav
2026-10-27 17:30 ` [PATCH 1/3] mm/memfd_luo: don't use memfd_pin_folios() Pratyush Yadav
2026-10-28 17:31 ` sashiko-bot [this message]
2026-10-28 20:18 ` Pasha Tatashin
2026-10-28 23:04 ` Pratyush Yadav
2026-10-29 0:01 ` Pasha Tatashin
2026-10-29 13:15 ` Pratyush Yadav
2026-10-27 17:30 ` [PATCH 2/3] mm: allow freezing i_pages Pratyush Yadav
2026-10-28 17:31 ` sashiko-bot
2026-10-27 17:30 ` [PATCH 3/3] mm: shmem: use mapping_set_frozen() for memfd preservation Pratyush Yadav
2026-10-28 17:31 ` sashiko-bot
2026-10-27 17:35 ` [PATCH 0/3] mm: allow freezing mappings David Hildenbrand (Arm)
2026-10-27 17:38 ` Pratyush Yadav
2026-10-27 18:59 ` David Hildenbrand (Arm)
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