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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 3f1490d57ef6-e9847dd4494sm836125276.30.2025.08.29.09.04.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Aug 2025 09:04:40 -0700 (PDT) Date: Fri, 29 Aug 2025 09:04:37 -0700 (PDT) From: Hugh Dickins To: Will Deacon cc: Hugh Dickins , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Keir Fraser , Jason Gunthorpe , John Hubbard , Frederick Mayle , Andrew Morton , Peter Xu , Rik van Riel , Vlastimil Babka , Ge Yang Subject: Re: [PATCH] mm/gup: Drain batched mlock folio processing before attempting migration In-Reply-To: Message-ID: <24905f30-4a7c-e627-a272-80977204ed68@google.com> References: <20250815101858.24352-1-will@kernel.org> <9e7d31b9-1eaf-4599-ce42-b80c0c4bb25d@google.com> <8376d8a3-cc36-ae70-0fa8-427e9ca17b9b@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Stat-Signature: o6ad3e37zhnrn4ne8wun75nngeujba7e X-Rspam-User: X-Rspamd-Queue-Id: 7712F1C0013 X-Rspamd-Server: rspam05 X-HE-Tag: 1756483482-628267 X-HE-Meta: U2FsdGVkX1/EwVYN6Pp8JU6eVQkKsudXk+KXtzSHM/V0GchhKvR54mB9VLm65vqAroEFOldjqbD/lFdMEcfGuFyl20PpOKV0SkZRdXjATNnR0GuqQ+ENSNHM0veaygiTRAwSbcZernF7x6VeZ7UI6oDHH01gc2ABCeTYjsjHYGSSRCr8y8Wvrd1eOaneGDkgpeWFdeIUTIIygv9rUVedNZhWFMgYzZFIPMxqMBUeGFoT6lFTDj9Lc6GuuUY1Fj2EaPTbkpZufVoUpO4jd1vi70zRulIs1icoSSf6V/T9Wvm0VAfIVD0jra/jhAWZeLA6EHi+6XYWbLV6z7R6wCzQeKx2pg94Q5N3XYKY8f15UXtu5BevssJ6JqO+Ljw0RIwA7O+kHwBDVzl/M1gaXarMonpmL4AmnvvCVkvby8mTt5CZzCJg9jIkCZW3WOpVoTrmS0+d5a9uBOwYXVu3cg4LsKzFLKL6M70bp/Q8F+FNqaRJQAjYKyDWMxjxy1Ydy6W1ScJ8yK22kZgGYsWXpwTRba+DPy01vuRaJQGvT/TTJ7KDaV1oR4S+9HrW6uBAD2tLd3mKXRuaYoinUKnU5nomnvCOfjqIm1qV/IkJVI691dBTLm8a5CiUiXi55wW/VVqI6xQo8+DsgYGFwhHYC/C5vjYXeJsnyRuUv7+jPdd9kDWsiMdGAiiiJrd6k8heIKaSO6B1MKD71HSgtV8QL8roOITAoWkPxr6b6oB/xLNWYWcjOKT0d7M0ugGjCEs45hWsm8FjpPezVsr+ZV8kvGKynG8byek+Pca8KSgRGiUx/0XsVT4dfnq8nlwLad9HPQgUqGPzqLhFuAH/BELU7kAEtiskq+REQKP3J1VPlQBYUIaSqkXmw2XPIsOvJY5sWmP7eAou2SNoRaY6p9hirWm8EWeQRgnNoRnsIJtzECquVWzjPK20DnkRUY/1HLKOG2Of+J3CUxUwadQ2Ddkz1cE ImhclQeR yyJtmG/KZXsAGXfr1YtZJ5x9L2ZJ0ym818PrezDk8CfGNLnAQFXVa+H2SM4WVW2wcnRRBFYwWnAAn0Mve/D3CjpqC5k3vqewL4GyoM7W/IM0v1KNLLzHRBtFP7PJ9zBEH8QnIUXwln+5ybTeH/XbYy1/iDxIrLvAVQ8prinNmii9bqwVWO9apHj8w1bRO1km2a5mTURvRmH64tZI/CYFjTxAU7vmjtjDtduKpIjotYDWZX31BV80QgwauQ0FOHkQvlVFnkTyAMoSAD5nW+axQpABXfbO51L8/GJ+0B8cqzoqcMFVXMySh4/W2HEpp5cMKQU/P X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Fri, 29 Aug 2025, Will Deacon wrote: > On Fri, Aug 29, 2025 at 12:57:43PM +0100, Will Deacon wrote: > > On Thu, Aug 28, 2025 at 01:47:14AM -0700, Hugh Dickins wrote: > > > Patch is against 6.17-rc3; but if you'd prefer the patch against 6.12 > > > (or an intervening release), I already did the backport so please just > > > ask. > > > > We've got 6.15 working well at the moment, so I'll backport your diff > > to that. > > Notwithstanding my question about the synchronisation, I cherry-picked > 86ebd50224c0 ("mm: add folio_expected_ref_count() for reference count > calculation") to my 6.15-based Android tree and applied your diff on top. Yes, I cherry-picked exactly that into my 6.12. Not a big deal, but a word of advance warning: the first patch in my series will (I believe) be a fix to that folio_expected_ref_count(), to allow for PG_private_2, which implies +1 on refcount (I've not yet researched whether it's +1 or +2 if PG_private and PG_private_2 are both set - comments I've seen imply +1 but I need to check). I thought of that when doing the cherry-pick because I thought that PG_private_2 had already been killed off by now in the latest tree: but was surprised to find that it is still there in 6.17-rc. > > With that, I've not managed to reproduce the original failure and > haven't observed any migration failures on the GUP path. Great, many thanks to you, Will. Hugh