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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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)" > > __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