From: Johannes Weiner <hannes@cmpxchg.org>
To: Kiryl Shutsemau <kirill@shutemov.name>
Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org,
usama.arif@linux.dev, lance.yang@linux.dev, ziy@nvidia.com,
hughd@google.com, baolin.wang@linux.alibaba.com,
baohua@kernel.org, liam@infradead.org, nico.pache@linux.dev,
dev.jain@arm.com, ryan.roberts@arm.com, balbirs@nvidia.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Kiryl Shutsemau (Meta)" <kas@kernel.org>
Subject: Re: [PATCH 2/5] mm/huge_memory: dequeue the deferred split after the split freeze
Date: Thu, 27 Aug 2026 12:59:14 -0400 [thread overview]
Message-ID: <20260827165914.GD3004@cmpxchg.org> (raw)
In-Reply-To: <20260826162101.1314941-3-kirill@shutemov.name>
On Wed, Aug 26, 2026 at 05:20:58PM +0100, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
>
> __folio_freeze_and_split_unmapped() takes the deferred split list_lru lock
> across the freeze. It is only there to stop deferred_split_scan() from
> touching the folio under split.
>
> With deferred_split_isolate() fixed, the workaround can be dropped.
>
> Unqueue the folio after folio_ref_freeze(), the way
> __folio_migrate_mapping() does: folio_unqueue_deferred_split() needs a
> zero refcount and a memcg still set, and both hold there.
>
> If the split is called from deferred_split_scan(), the unqueue is a
> no-op -- the folio is already removed from the list. But
> PG_partially_mapped is still set, so it has to be cleared here or
> MTHP_STAT_NR_ANON_PARTIALLY_MAPPED never comes back down.
>
> Assisted-by: Claude-Code:claude-opus-5
> Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Infinitely better!
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
next prev parent reply other threads:[~2026-08-27 16:59 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-26 16:20 [PATCH 0/5] Fix deferred_split_isolate() and clean up __folio_freeze_and_split_unmapped() Kiryl Shutsemau
2026-08-26 16:20 ` [PATCH 1/5] mm/huge_memory: do not touch frozen folios in deferred_split_isolate() Kiryl Shutsemau
2026-08-26 16:45 ` Zi Yan
2026-08-27 15:02 ` Johannes Weiner
2026-08-27 15:23 ` David Hildenbrand (Arm)
2026-08-27 15:38 ` Zi Yan
2026-08-27 15:56 ` David Hildenbrand (Arm)
2026-08-27 16:38 ` Usama Arif
2026-08-28 1:57 ` Zi Yan
2026-08-31 0:33 ` Kiryl Shutsemau
2026-08-26 16:20 ` [PATCH 2/5] mm/huge_memory: dequeue the deferred split after the split freeze Kiryl Shutsemau
2026-08-26 17:10 ` Zi Yan
2026-08-27 15:25 ` David Hildenbrand (Arm)
2026-08-27 16:59 ` Johannes Weiner [this message]
2026-08-26 16:20 ` [PATCH 3/5] mm/huge_memory: reduce indent level in __folio_freeze_and_split_unmapped() Kiryl Shutsemau
2026-08-26 16:34 ` Zi Yan
2026-08-26 16:43 ` Kiryl Shutsemau
2026-08-26 16:21 ` [PATCH 4/5] mm/huge_memory: fold nested ifs " Kiryl Shutsemau
2026-08-26 16:21 ` [PATCH 5/5] mm/huge_memory: turn the swapcache-with-mapping error case into an assert Kiryl Shutsemau
2026-08-28 3:14 ` [PATCH 0/5] Fix deferred_split_isolate() and clean up __folio_freeze_and_split_unmapped() Balbir Singh
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