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h=Date:From:To:Cc:Subject:In-Reply-To:References; b=EgIGL3FbRxeU5XW2xULyYeljHqCqhy6r6Wkwtxz0U6rEWEYJNOBAW4QS1+i9XzI4r gVnFCttP3qStKohiNNiAuxXCWR+8cOBlZRFOBZqhSMh7qT3a8E0kqkHU8vd6r468US ARj7HeSZzPe34bjt3YF01R/085aCSLysmxJE18Q8= Date: Sat, 1 Aug 2026 12:20:40 -0700 From: Andrew Morton To: Hugh Dickins Cc: "David Hildenbrand (Arm)" , Jason Gunthorpe , John Hubbard , Peter Xu , Kiryl Shutsemau , Ackerley Tng , Frank van der Linden , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/gup: fix always draining LRU caches in collect_longterm_unpinnable_folios() Message-Id: <20260801122040.7230a8eb0dc846ce357fba67@linux-foundation.org> In-Reply-To: References: <20260731-check_and_migrate_movable_folios-v1-1-e0002d7b791e@kernel.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-Server: rspam12 X-Rspamd-Queue-Id: 921221C0007 X-Stat-Signature: rap5ri8rcz5kaegxyndwqznqm8qxyzze X-Rspam-User: X-HE-Tag: 1785612042-77554 X-HE-Meta: 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 cIkYkVMY OXyzb1mVQq1VXp0qaUXR2GQRYYLhne966ytk3XeFAnPny1q1O18IsFOj807lob7gync236G6zwTesxXd7BRSMQXOH7jZ1af0Usv/4iSbK7v2mkmGDGSlw4VxM3YSZzmJeAYSZMS3sNRInQzj6AlFDZD5QWWPhcw8S/O/zdT1qCrkCQUL9D8FFhKVCUq7PzRQwrPMyE1QmTYyigq82RzykyYNfzQpInAq/jnXt1WIHOIO+DDXvPPtLpSBG22V951wVz/t60IMh5T2+Mb9B7IOtOTG0pDMiGI+nyPbXPREtbLLVg5ioQ0PDkCLrxhuKp7lFg3w4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 1 Aug 2026 11:49:39 -0700 (PDT) Hugh Dickins wrote: > > Found by code inspection. If someone has a testcase that can easily > > trigger this and result in migration problems, please test! But this > > change seems to be "obvious the right thing to do". > > Sorry, I don't (as perhaps is too obvious). And I'm a wee bit afraid > that some of the problems which those changes happened to succeed in > fixing, might now reappear once the drains are finely targeted. > > Am I arguing for a delay before advancing to stable? Perhaps, but > I think not: it's probably best to get that working as intended, > then deal with any fallout if it arises: just be on guard. This patch is in mm-new, so it's still some months away from -stable eligibility.