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Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pasha Tatashin , Peter Xu , Alistair Popple , Jason Gunthorpe Subject: Re: [PATCH v2 14/17] mm/damon: handle device-exclusive entries correctly in damon_folio_young_one() Date: Mon, 10 Feb 2025 22:59:19 -0800 Message-Id: <20250211065919.5935-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250210193801.781278-15-david@redhat.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 65E91A000D X-Stat-Signature: mpensipjb8sj9r6s1x83npgqh59m6d34 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1739257163-140788 X-HE-Meta: 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 9EjyQLM+ 9K/nzMuMQSIG9StsMrnKPSSXI1fvaxfet1BBk3kz6SOHbEYE4zAuvoGXUwRHxrbW4dXvK0EUTHCgCR5CFS89uyWmAjIaDDjmWb2y92g5m4SPQtVm2gYmwweKr716s7PXLrSoXJPYLVGh+KfhWL2U6OP7vB+paQOh+YZf1fqskY/hdH6dQ56d1vfdhAKJPIf2FWaU3oer6FrZ9SlOHMqKBastvVetn8/LuzcKbIiotSuDCAzSsk/G/mvjytJ+SXzkz5SGoT0kRhPSHw3K6DA6nqy6+whxbWZlI7UTDwYiJoCbibq+wo9f82wdCeg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000011, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 10 Feb 2025 20:37:56 +0100 David Hildenbrand wrote: > Ever since commit b756a3b5e7ea ("mm: device exclusive memory access") > we can return with a device-exclusive entry from page_vma_mapped_walk(). > > damon_folio_young_one() is not prepared for that, so teach it about these > PFN swap PTEs. Note that device-private entries are so far not applicable > on that path, as we expect ZONE_DEVICE pages so far only in migration code > when it comes to the RMAP. > > The impact is rather small: we'd be calling pte_young() on a > non-present PTE, which is not really defined to have semantic. > > Note that we could currently only run into this case with > device-exclusive entries on THPs. We still adjust the mapcount on > conversion to device-exclusive; this makes the rmap walk > abort early for small folios, because we'll always have > !folio_mapped() with a single device-exclusive entry. We'll adjust the > mapcount logic once all page_vma_mapped_walk() users can properly > handle device-exclusive entries. > > Fixes: b756a3b5e7ea ("mm: device exclusive memory access") > Signed-off-by: David Hildenbrand Reviewed-by: SeongJae Park Thanks, SJ [...]