From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DE9F536166C for ; Fri, 16 Jan 2026 10:51:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768560684; cv=none; b=EQpqVIEUeuVEUJZzeif49dNiVNjj2p40nh4MjQlzp3FhH6r79L0Hdx1BGyMHMdA2pKGods6uGG+kFwVa/SuVISdWlYQPESoVBNO5PnRoGYVeWLWPctWw7jFSzEdFplMIraq+45krV3fs6qFEpmCPI5OAHP31RiN5ttsMpKqwHIo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768560684; c=relaxed/simple; bh=rFY9xlBxTcO5q7oAPkLGToaIjHoIexlwDVGdEZseowE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=el4d1f6GL7g1+guVh+7VUEySz6LZzEOBVIoTETJBIa9PlsxJEYi/qGLejTSBHYhvyUeM5H8YcCQ8aL+UMLmIH6zCJyx9cjubbPpouy2yXIqplrRa3iwbuWaLDlTxgPoXUSx5W7ve8xjcrzIQTngDkoy6rklTFfu7pfXFfgmSJis= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=D7lZljhE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="D7lZljhE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A495C19421; Fri, 16 Jan 2026 10:51:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768560684; bh=rFY9xlBxTcO5q7oAPkLGToaIjHoIexlwDVGdEZseowE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=D7lZljhEaM8EZsQZkib/DBBz4E2jIkdHSOXRdXaT3UyzCaw1B043eK/BUrQfGXKQD WYufWQmpgBxWLs0vBWa4it1La8XZaoby0CPydcmctlompiEpR35FLxgovt7jQ1KSSj n+RnWxxw2P8Zm79JddxnB1y/hGjRdlDQw/m3IsA/2Pw3dPLD2tBbPoZZbyNf/yWPmY //WZsrdDMZFsTlpsy+WcjjThVDXHRLKlKyvZu2Mu69L9WPxbXtu4QEvLlKoQ9r9YpQ L6k6X0pf/YkbeKRyPt6zA1FZGrmvCr27y/d3+vszoGnqUH/2OV6GwOq2DJcHEUiMMX m9+3TDLV3emvQ== Message-ID: <5af933d1-8c64-4d3c-b835-d90c8e9f771a@kernel.org> Date: Fri, 16 Jan 2026 11:51:17 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable] mm: Fix uffd-wp bit loss when batching file folio unmapping To: Dev Jain , Lorenzo Stoakes , akpm@linux-foundation.org Cc: axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, ryan.roberts@arm.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260116082721.275178-1-dev.jain@arm.com> <343f8462-44fd-4190-9fe2-8120b5403269@lucifer.local> <4b784eef-e874-45a6-828a-4fc2acab6fb7@arm.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAa2VybmVsLm9yZz7CwY0EEwEIADcWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaKYhwAIbAwUJJlgIpAILCQQVCgkIAhYCAh4FAheAAAoJEE3eEPcA/4Naa5EP/3a1 9sgS9m7oiR0uenlj+C6kkIKlpWKRfGH/WvtFaHr/y06TKnWn6cMOZzJQ+8S39GOteyCCGADh 6ceBx1KPf6/AvMktnGETDTqZ0N9roR4/aEPSMt8kHu/GKR3gtPwzfosX2NgqXNmA7ErU4puf zica1DAmTvx44LOYjvBV24JQG99bZ5Bm2gTDjGXV15/X159CpS6Tc2e3KvYfnfRvezD+alhF XIym8OvvGMeo97BCHpX88pHVIfBg2g2JogR6f0PAJtHGYz6M/9YMxyUShJfo0Df1SOMAbU1Q Op0Ij4PlFCC64rovjH38ly0xfRZH37DZs6kP0jOj4QdExdaXcTILKJFIB3wWXWsqLbtJVgjR YhOrPokd6mDA3gAque7481KkpKM4JraOEELg8pF6eRb3KcAwPRekvf/nYVIbOVyT9lXD5mJn IZUY0LwZsFN0YhGhQJ8xronZy0A59faGBMuVnVb3oy2S0fO1y/r53IeUDTF1wCYF+fM5zo14 5L8mE1GsDJ7FNLj5eSDu/qdZIKqzfY0/l0SAUAAt5yYYejKuii4kfTyLDF/j4LyYZD1QzxLC MjQl36IEcmDTMznLf0/JvCHlxTYZsF0OjWWj1ATRMk41/Q+PX07XQlRCRcE13a8neEz3F6we 08oWh2DnC4AXKbP+kuD9ZP6+5+x1H1zEzsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCgh Cj/CA/lc/LMthqQ773gauB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseB fDXHA6m4B3mUTWo13nid0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts 6TZ+IrPOwT1hfB4WNC+X2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiu Qmt3yqrmN63V9wzaPhC+xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKB Tccu2AXJXWAE1Xjh6GOC8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvF FFyAS0Nk1q/7EChPcbRbhJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh 2YmnmLRTro6eZ/qYwWkCu8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRk F3TwgucpyPtcpmQtTkWSgDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0L LH63+BrrHasfJzxKXzqgrW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4v q7oFCPsOgwARAQABwsF8BBgBCAAmAhsMFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmic2qsF CSZYCKEACgkQTd4Q9wD/g1oq0xAAsAnw/OmsERdtdwRfAMpC74/++2wh9RvVQ0x8xXvoGJwZ rk0Jmck1ABIM//5sWDo7eDHk1uEcc95pbP9XGU6ZgeiQeh06+0vRYILwDk8Q/y06TrTb1n4n 7FRwyskKU1UWnNW86lvWUJuGPABXjrkfL41RJttSJHF3M1C0u2BnM5VnDuPFQKzhRRktBMK4 GkWBvXlsHFhn8Ev0xvPE/G99RAg9ufNAxyq2lSzbUIwrY918KHlziBKwNyLoPn9kgHD3hRBa Yakz87WKUZd17ZnPMZiXriCWZxwPx7zs6cSAqcfcVucmdPiIlyG1K/HIk2LX63T6oO2Libzz 7/0i4+oIpvpK2X6zZ2cu0k2uNcEYm2xAb+xGmqwnPnHX/ac8lJEyzH3lh+pt2slI4VcPNnz+ vzYeBAS1S+VJc1pcJr3l7PRSQ4bv5sObZvezRdqEFB4tUIfSbDdEBCCvvEMBgoisDB8ceYxO cFAM8nBWrEmNU2vvIGJzjJ/NVYYIY0TgOc5bS9wh6jKHL2+chrfDW5neLJjY2x3snF8q7U9G EIbBfNHDlOV8SyhEjtX0DyKxQKioTYPOHcW9gdV5fhSz5tEv+ipqt4kIgWqBgzK8ePtDTqRM qZq457g1/SXSoSQi4jN+gsneqvlTJdzaEu1bJP0iv6ViVf15+qHuY5iojCz8fa0= In-Reply-To: <4b784eef-e874-45a6-828a-4fc2acab6fb7@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/16/26 10:40, Dev Jain wrote: > > On 16/01/26 2:09 pm, Lorenzo Stoakes wrote: >> On Fri, Jan 16, 2026 at 01:57:21PM +0530, Dev Jain wrote: >>> The recently added file folio unmap batching support forgets to update >>> pte_install_uffd_wp_if_needed(), which still updates a single pte. >>> We end up jumping to the end of the folio in page_vma_mapped_walk(), thus >>> setting the uffd-wp marker only on a single pte in the batch. Fix this by >>> passing nr_pages into the function, and set the uffd-wp marker on all ptes. >>> >>> Note that, since the nr_pages passed to this function is always derived by >>> some sort of batching, it is guaranteed that the set of old ptevals of the >>> batch have uffd-wp bit on all ptes or no ptes, therefore it is safe to derive >>> the value of the local variable "arm_uffd_pte" from only the particular >>> pteval passed to this function, but apply the result on all ptes of the batch. >>> >>> Use set_pte_at() in a loop to set the markers - we cannot use set_ptes() >>> as that will increment the PFN, but we don't have any PFN to update here. >>> >>> The userspace visible effect of the bug is inaccuracy observed by workloads >>> relying on uffd-wp regions to install their own pages. >>> >>> Fixes: 8798e255b5ec ("mm: rmap: support batched unmapping for file large folios") >> Hmm this patch isn't upstream yet, so wouldn't this patch be better as a comment >> replying to the series so it can be respun? >> >> You only do a fixes tag for either upstream things that obviously have to stay >> in place or perhaps things in mm-stable immediately prior to merge window that >> can't be adjusted. > > I saw that the last comment on that series was more than a week back, so best > thought to just do a folded fix on top of it - and I had formed the impression > (from the conversations on list) that akpm prefers fixes over respins : ) That series is still on my TODO list and I hope Andrew will keep it out of stable until I get to it. Hope is all I got ;) -- Cheers David