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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=fnLEbREK; 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 EBF89606A321; Mon, 26 Oct 2026 23:25:09 +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=fnLEbREK Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCE9C1F031E0; Mon, 26 Oct 2026 23:25:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793057109; bh=k1Zlag/DNuh0RzHvANliw7JgpC1PTEsuWY1OUAoAx8Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=fnLEbREKUCIw3x3D22mrcZnRxIlnJim3GobgkFHE+QN5rPvlAjVqot2WvzRAG1xKA 5H7kD8aq2n70G55NtkQDHhj7rYvSZefDvllEGiQIq5tVGRQZnpBGDZwlWt9kr9nXjD KT9w8JmxAv+rDcqcSEaH42DuiiIcSduz+eeDMkp8Eb1qL9xHOOIwY9t463bHSIcHJa qlO6fVGU43GVMPDuQtga3X8z75Z/YHhduXBbnXNHKzHp32YroM2VQCfMAvUvQqY/0h 5hSZkqRt/bf2hTQsQcrmxRUn1ge8dnuh0mYqMYmY13+1QLbdmwGOEsVckCCPrZ2ejt y29huz6g4kJCw== Message-ID: Date: Tue, 27 Oct 2026 00:24:46 +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 07/16] mm/shmem: avoid moving the truncation start backwards To: Zi Yan , Andrew Morton , Zhang Yi Cc: Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Johannes Weiner , Vladimir Davydov , Michal Hocko , Hugh Dickins , Baolin Wang , Lukas Czerner , Carlos Maiolino , Christian Brauner , Jan Kara , Daniel Verkamp , Jeff Xu , Muchun Song , Oscar Salvador , David Stevens , "Matthew Wilcox (Oracle)" , William Kucharski , Chris Li , Kairui Song , Nhat Pham , Miaohe Lin , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Mason , stable@vger.kernel.org References: <20261026-fixes_shmem-v1-0-703206d5fa0c@kernel.org> <20261026-fixes_shmem-v1-7-703206d5fa0c@kernel.org> <2E377C76-D62C-4A2A-94E3-ABC40C6FCDD2@nvidia.com> <583728ed-dc63-4685-9ac5-5a980db55973@kernel.org> <0D22B04E-5730-4D3A-ADA6-9F1AF94F06AA@nvidia.com> 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 10/27/26 00:16, Zi Yan wrote: > On 26 Oct 2026, at 18:39, Zi Yan wrote: > >> On 26 Oct 2026, at 17:13, David Hildenbrand (Arm) wrote: >> >>> >>> How confident are we that it fixes the same issue? >> >> The issue here is that folio_next_index(folio) used in the mainline >> code can be an index lower than lstart and the fix is use max() >> to prevent start going backwards. (I wrote this to make sure >> I understand the issue correctly) >> >> Zhang Yi’s patch passes start into truncate_inode_parital_folio(), >> which has a new signature, and it is updated with the folio’s index >> within the [lstart, lend] range at the beginning. >> >> So this patch fixes the issue at the caller and Zhang Yi’s patch >> fixes the issue inside truncate_inode_partial_folio(). >> >>> >>> Does it also cover #8? >> >> No, patch 8 is still needed. I am checking it on how to rebase it >> on mm-stable. >> >> Patch 9, 10, 11 might need rebase on mm-stable too. >> >> Since these patches are on top of mainline instead of mm-stable, >> you will need to rebase them. IIRC, Zhang Yi’s patches are needed >> for ext4 + iomap buffered I/O conversion. Hmm, but Zhang Yi’s >> ext4 iomap patches has landed in mainline but its dependency >> is not. So we cannot drop Zhang Yi’s patches and ask for a >> resend. Adding Zhang Yi here. > > To clarify the dependency, without Zhang Yi’s > truncate_inode_partial_folio() patchset, the ext4 + iomap changes > would cause data loss. We probably want to get Zhang Yi’s patches > in first to avoid that. Ugh, what a mess. > > Patch 7 to 11 do not apply cleanly on top of mm-stable due to Zhang Yi’s > truncate fix, where > > 1. patch 7 can be dropped as I discussed above, > 2. patch 8 needs a folio->mapping guard for the added statement, > 3. patch 9-11 can be applied with fuzzy, but I need to look into > them about functionalities before fully trust what LLM says. Yeah, let me take a look tomorrow. I cannot put into words how much this shmem + pagecache shite annoys me. What a piece of crap people created here. And looking at the massive changes to fix stuff, what a piece of crap people are creating. I better go to sleep now :) -- Cheers, David