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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=BUOGHtk2; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ABD0A606A33B; Mon, 2 Nov 2026 06:53:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=BUOGHtk2 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0E3FB1F000C1; Mon, 2 Nov 2026 06:53:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793602424; bh=i15daf++VpfZRCz0DvkW9BbXArZ1yonaTYUXl4oTyl8=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=BUOGHtk2kOh7f3R1hPSmZ2ETTobY+Xi9BDxsQWKDy/S7Dr6is7pmvBxEv6SrrkwVi VisOlvZrsPUOADAovsZVlV9283ZoLJ4WGG7bKIai0IJrB9ZuzpzmH33BSF2uUA6+wH QAclpf/RgRyDgjLesfyKFNtGgYvqSOKNdcjAt7I6OU5oHO8fVHIdmwP86LjwS2ykwJ j/d20ewplqwUYh66fKQNil+pxfb0DqdN26D2lzqDFH11Jbv+8u1iZjtfSg4nmrgj/+ 4hmcOspD9jf79gw4Y85tysbe8CqQfgQfRX9oVPrjt5Jsta4aYKTdW5U5ZJIrmpILhy KeuOlyCG8x/RQ== Message-ID: <4211a96c-681c-4b87-8094-4f6c824ffbbf@kernel.org> Date: Mon, 2 Nov 2026 07:53:39 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/swapfile: drop a large unmapped swap-in folio in unuse_pte() To: Mani Tofigh , Andrew Morton , Chris Li , Kairui Song Cc: Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , linux-mm@kvack.org, linux-kernel@vger.kernel.org, tz2294@columbia.edu, stable@vger.kernel.org References: <20261030-swapin-large-unmapped-v1-1-41e4ae378e6c@columbia.edu> <04ad7001-bdd4-47e1-9a80-5b2464da1044@kernel.org> <930e2b99-df87-4aeb-88d0-d12d012edbf1@columbia.edu> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 11/1/26 16:46, Mani Tofigh wrote: > On 10/30/26 6:15 PM, David Hildenbrand (Arm) wrote: >> Why is this special to large folios? I guess because a single PTE keeps the >> large folio alive, right? > > Yup. For a small folio the one PTE maps all of it so > folio_add_new_anon_rmap() is fine there. For a larger one it marks > every page as mapped and exclusive even though only one PTE got mapped. > >> Can you pack the existing handling in do_swap_page() into a helper, pass >> nr_pages, and reuse it here? > Sounds good, I'll do that in v2 and send it against mm/core.git > for-next.  One small thing in the helper you suggested though: > the first check should be folio_test_anon() instead of > !folio_test_anon(), otherwise a large non-anon folio would > still get mapped. Was just a quick hack to se what we could do with the function name. With the VM_WARN_ON_ONCE() we might also just move the folio-swapbache dropping to the caller, leaving the VM_WARN_ON_ONCE() check in there. Yes, please resend against core.git, thanks! -- Cheers, David