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Thu, 27 Aug 2026 09:59:15 -0700 (PDT) Date: Thu, 27 Aug 2026 12:59:14 -0400 From: Johannes Weiner To: Kiryl Shutsemau 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)" Subject: Re: [PATCH 2/5] mm/huge_memory: dequeue the deferred split after the split freeze Message-ID: <20260827165914.GD3004@cmpxchg.org> References: <20260826162101.1314941-1-kirill@shutemov.name> <20260826162101.1314941-3-kirill@shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260826162101.1314941-3-kirill@shutemov.name> X-Stat-Signature: ab5q3aoeewidc41x4h7ud69sh9yubmmk X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 56ED5100003 X-Rspam-User: X-HE-Tag: 1787849957-906516 X-HE-Meta: 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 bITInEKZ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 26, 2026 at 05:20:58PM +0100, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" > > __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) Infinitely better! Reviewed-by: Johannes Weiner