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b=iynWM0D4SUypA8wlnsvN9Nb8wXTGYvUrZyHq3YXnX4a0GasUjitdrA6P4X/aXdVlJ Uty182SdFlDkGEHq8oVt4FYAu0vfPMp+tZKOE9iUJCLbHXMD0JofkLOyoRWljN8aUH HmTETDXB607mjyh8boIhMKHTnk5lUM6C/K5yNkVA= Date: Sat, 14 Mar 2026 15:40:42 -0700 From: Andrew Morton To: Usama Arif Cc: SeongJae Park , npache@redhat.com, david@kernel.org, ziy@nvidia.com, willy@infradead.org, linux-mm@kvack.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, hannes@cmpxchg.org, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-kernel@vger.kernel.org, kernel-team@meta.com, richard.weiyang@gmail.com, stable@vger.kernel.org Subject: Re: [PATCH v3] mm: migrate: requeue destination folio on deferred split queue Message-Id: <20260314154042.327ba957b1a8c10f64ae0169@linux-foundation.org> In-Reply-To: References: <20260312104723.1351321-1-usama.arif@linux.dev> <20260313001630.80081-1-sj@kernel.org> <20260312175241.01b876f3b325264f43312d79@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 1E1151A0002 X-Rspamd-Server: rspam07 X-Stat-Signature: p5kz1imujhmb89e5cw1jrfzrx9u3gssm X-Rspam-User: X-HE-Tag: 1773528044-826654 X-HE-Meta: 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 mYmWYTSD Ky4kYqozwFRp/Wk3DYaWbE9TyeyMhDokbboE0uNJEmg9z28rZ+7beO/Rb46C+6ibobIrvuiSZtR7F12slTx2uQncrIX2pDqOwZB9ldordGzFh+R4MDEQASXuNvLnlR55m/Df1X3+lGrDcvXZEDBrzl/ebRR42jAT0uUIuqpI7AMTgRSWmJGhEwVVOVUNISfd/j/cScyQEveZ6mJFeQpR8CpwaL6OMmEEU2QHmCJA35cgDES8hhD2Kg4DCowysYVZPzZ5WxkCUF3qfW9Md6bf1REmpT6gIYdv+gfAqbg/vjErbgvMWrvPfnlUO9R/LbqnH21LbuYx8wF8403gOtGVkOZx61GL2WIp3zq9G226a3XjonN+88tJpJ8AqiGIyDl6QfCruEjcbAgMz7rlzlJe1peOSqA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 13 Mar 2026 13:40:29 +0300 Usama Arif wrote: > > > On 13/03/2026 03:52, Andrew Morton wrote: > > On Thu, 12 Mar 2026 17:16:30 -0700 SeongJae Park wrote: > > > >>> By the time migrate_folio_move() runs, partially mapped folios without a > >>> pin have already been split by migrate_pages_batch(). So only two cases > >>> remain on the deferred list at this point: > >>> 1. Partially mapped folios with a pin (split failed). > >>> 2. Fully mapped but potentially underused folios. > >>> The recorded partially_mapped state is forwarded to deferred_split_folio() > >>> so that the destination folio is correctly re-queued in both cases. > >>> > >>> Reported-by: Johannes Weiner > >>> Fixes: dafff3f4c850 ("mm: split underused THPs") > >> > >> Seems the commit is merged in 6.12. And I assume the user impact on > >> THP-shrinker enabled systems is visible. If so, should we Cc stable@ ? > > > > I think the user impact should be visible to backport, but the > > changelog is elusive on details? > > > > > The original patches added THPs to deferred_list at fault/collapse, they > got removed but not added back to the list after migration. > This patch adds them to the deferred_list on migration. The user would > not expect the THPs to get removed from deferred_list on migration, so > this fixes user expectations. Maybe users just won't notice? If we can't identify any benefit to userspace then I don't think this patch meets the criteria for backporting. > I have CC-ed stable@vger.kernel.org to this email. Should I resend the patch > with CC stable in commit message? That's OK, I update changelogs. A lot.