From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DA72260A2603 for ; Thu, 29 Oct 2026 14:18:47 +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=XUQVHCdI Received: by kanga.kvack.org (Postfix) id D8D556B05BC; Thu, 29 Oct 2026 10:18:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D65026B05BD; Thu, 29 Oct 2026 10:18:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C545B6B05BE; Thu, 29 Oct 2026 10:18:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 8CE7A6B05BC for ; Thu, 29 Oct 2026 10:18:46 -0400 (EDT) Received: from smtpin19.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 16732A0435 for ; Thu, 29 Oct 2026 14:18:46 +0000 (UTC) X-FDA: 85375869852.19.79F1EBD Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf29.hostedemail.com (Postfix) with ESMTP id 666F8120012 for ; Thu, 29 Oct 2026 14:18:44 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XUQVHCdI; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf29.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793283524; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=KrmJHHnmWU49kR3EjjGIqe7TD1rMMa5OKGo7QYF6nE0=; b=yIwOdueAkCgJ6plVmjejKDyj5O3c91bCMJFEiRgCJXPpm9SJk2iNlYWXQ3S0VfbH/TLLxD DUzOIOaM3qd+LFQuOlrgRLbMibBMDaPjpmJP9/5huGduj0ABGDlc+bEAtQkmcPtS3s1gK3 ry3nAr2JXVEWo4X+6Dgz0rDvWz9lJe4= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XUQVHCdI; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf29.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793283524; b=amCoq19SwqbkulceccGvSDrqtPCk8tTQDocqISXqbCiarRw7v3e/j39LnfIzZ6M6kKlNUI R6JlwLfxeXRWv5b+GmiWtMCGmjgkPwXf6FVqP/ncHtklwBMx7OOURQfkBZTWbiikpA5QYn hCdnhN8p/J+cpuhnOlf7TbMS3z2mmuM= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 9F9506022F; Thu, 29 Oct 2026 14:18:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37A8D1F01825; Thu, 29 Oct 2026 14:18:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793283523; bh=KrmJHHnmWU49kR3EjjGIqe7TD1rMMa5OKGo7QYF6nE0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=XUQVHCdIXfvmbaph/VA/rxWkBrBMpTWNrTAYGGhlCnhClgHcbmqfLm/eKiQyCpl+W E3eYifg9BPWiMSDXEftsG6P1erQcEU1cxEqVv7Q65NLTq6sRGvicyug8evlSykwQ1n N555FxgSSTArXb9eRt1k/+Rr7/gKg542EG3ZHgkCdrsxx5r9mVZUcQFcOovPpa8Tf+ K5DX1M/2E6C5yMjxDhwgcHRNE2N173N/c0Ut2AaVXgOtOHtG0XhsZlbs8t2w98oJlg Mu1VOIE7670qxMrHyiu6QL0I/NiamJbSsCKr41PrvWSm0g6yo0ne75ilTxt7hUJyj/ vpESVobE2Pi8Q== Message-ID: <7fab2115-6c44-43b1-b03b-8ce4a37ffe32@kernel.org> Date: Thu, 29 Oct 2026 15:18:23 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 05/46] mm/truncate: look again if a folio left the mapping To: Kiryl Shutsemau Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, Josef Bacik References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-5-6f74bec9a5bb@kernel.org> <2f2ef336-2186-4f20-b7f5-565e60471bda@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 666F8120012 X-Stat-Signature: scea6sq6x7zzpgcsrasw5dfbubfphmf7 X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793283524-614958 X-HE-Meta: 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 MvALH8MI AUpdybM2jQHVDlCqhhbWbEOI1rhSAC8lHQfyBOx9PP6HUMkHJgKsedBNft2t7lua69LZ4wZeVdxuITONKbz25Uk7ZQcB/53Az75wA/g4LLoBSD6Hd55QpbsGyh92af8ajYWXU1BYLMFQbaXMH63vZ3iuimOfb9GMf/wLe7qTWQkGJ91pb7PjL2O6OOtjyymnHY8ZPoreZAxh98dZr82LbDbcXIHC6JFge7g4JlHtAJo3iRNEjSFwkLynsiSTfJdJ4rMFMNAWJQRiZIj010DE/3DZrBVhW8fkGcv76FfVx6rswyWq9HkACVDmnChiN9YzkZ4Vr0VBKp85vg7NZROQD7ZyTaOjI/Q8MmM4vnyXJejF0p0s= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/29/26 12:37, Kiryl Shutsemau wrote: > On Wed, Oct 28, 2026 at 10:45:34PM +0100, David Hildenbrand (Arm) wrote: >> My brain hurts, does the above make sense? > > Yes, I missed that the loop only goes back to start when a lookup > comes back empty below end. When the last batch reaches end, it exits > without another look. It doesn't need the split either: any punch hole > whose last page is in the page cache gets there. > > That exit looks unintended to me. b9a8a4195c7d ("truncate,shmem: Handle > truncates that split large folios") turned the "if (start >= end) goto > out" early exit into the loop condition. Before it, the loop went back > to start until a lookup from start found nothing; Hugh kept that on > purpose for hole punch in 792ceaefe621 ("mm/fs: fix pessimization in > hole-punching pagecache"). > > Restoring it is enough, and makes the "restart to make sure all gone" > comment true again: > > + if (start >= end) > + return; > + > index = start; > - while (index < end) { > + for (;;) { > > Then a replaced folio is found on the next round, and truncate needs no > special case for it. > But that's then another lookup even if not really required? Why do you thing that is that better? I agree that the code is simpler, but at least it's consistent with the other handling. -- Cheers, David