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 17A592E62AC; Mon, 11 May 2026 13:34:22 +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=1778506463; cv=none; b=EItITKMhBFcN+7t3F4xA+JKihFCSqtt00fSTvJmj8CJM+hnOsSCqLlLkdkS34aiFti9cvyr8/aOfXNzN/xlC/uTApdEIjwCRU/T4VF5SGLk7wCyUu4MDBXyEUHbFTXVjmONgxaqp/SFUEzM5qyNcqh3ax1JhHRjMrAyoikqa2PE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778506463; c=relaxed/simple; bh=j72HTubFsOIYbMEtyYXlD7M5D6HK3LB8/kEeO2w5Bew=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rtPFotzIrZJ7q//+TDBnaL44Yx5YdleU+Sts2KUlLEku1xRmtbdHFffpuGmSsmFoPRIXg2Hbc+04Bn30s68qOmUn0AGEG0R/x4niUYHbJpb7oEG75yzpDMqfQtjfAyr4bU9UjZnhEStBho2Qgmoz9LoKNZrhItK5lKF0VlO66h8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T2BnNcIN; 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="T2BnNcIN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8302C2BCB0; Mon, 11 May 2026 13:34:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778506462; bh=j72HTubFsOIYbMEtyYXlD7M5D6HK3LB8/kEeO2w5Bew=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=T2BnNcIN5YScjHD3wtjb9RNuQ6p/Vt806Q4CVEAghjtFothkBtEcrBmAkRqRvkqV6 vn96MWKfiCRLLviFkKZknm/h50Qc78gweh0eS/bH9aZfDwm8mnZrhUk81DIE2ojbdE 62yLypWWFnTJtYy9f4Rh2SffC7ZK1iI/1pT8sQDJXI8pq8053xLOrC18vuhZqRQtFb RtG6U+hlY00P1f0J1y5OUAnaQAM7FDlMPhnZ7vK4JKANBPz3wVKkQKn4ow8kHWxjy4 bmxFWeN7b/GFT0WiLPNzdbtaSqTe2Do7X1MbWtycbj0NvB8+N9lqIIVa/kqE+DGgXB J3aMfMxp2bWLA== Message-ID: <71d77e4e-8441-4575-acfb-ac81ab57ec95@kernel.org> Date: Mon, 11 May 2026 15:34:17 +0200 Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 2/3] mm: track DONTCACHE dirty pages per bdi_writeback To: Jeff Layton , Christian Brauner , Linus Torvalds , Christoph Hellwig Cc: Alexander Viro , Jan Kara , "Matthew Wilcox (Oracle)" , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Mike Snitzer , Jens Axboe , Ritesh Harjani , Chuck Lever , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org References: <20260511-dontcache-v7-0-2848ddce8090@kernel.org> <20260511-dontcache-v7-2-2848ddce8090@kernel.org> <20260511-begonnen-zuwege-b4272b78eb00@brauner> <960ba89c3c6a04a7b9137322493d65e4ab4cd7d2.camel@kernel.org> From: "David Hildenbrand (Arm)" 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <960ba89c3c6a04a7b9137322493d65e4ab4cd7d2.camel@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/11/26 15:29, Jeff Layton wrote: > On Mon, 2026-05-11 at 15:10 +0200, Christian Brauner wrote: >> On Mon, May 11, 2026 at 07:58:28AM -0400, Jeff Layton wrote: >>> Add a per-wb WB_DONTCACHE_DIRTY counter that tracks the number of dirty >>> pages with the dropbehind flag set (i.e., pages dirtied via RWF_DONTCACHE >>> writes). >>> >>> Increment the counter alongside WB_RECLAIMABLE in folio_account_dirtied() >>> when the folio has the dropbehind flag set, and decrement it in >>> folio_clear_dirty_for_io() and folio_account_cleaned(). Also decrement it >>> when a non-DONTCACHE lookup atomically clears the dropbehind flag on a >>> dirty folio in __filemap_get_folio_mpol(), using folio_test_clear_dropbehind() >>> to prevent concurrent lookups from double-decrementing the counter, and >>> guarding the decrement with mapping_can_writeback() to match the increment >>> path. >>> >>> Transfer the counter alongside WB_RECLAIMABLE in inode_do_switch_wbs() so >>> that the stat is properly migrated when an inode switches cgroup writeback >>> domains. >>> >>> The counter will be used by the writeback flusher to determine how many >>> pages to write back when expediting writeback for IOCB_DONTCACHE writes, >>> without flushing the entire BDI's dirty pages. >>> >>> Suggested-by: Jan Kara >>> Assisted-by: Claude:claude-opus-4-6 >> >> Picking up on something we discussed at LSFMM in one of the sessions as >> an aside rant: I find these AI Assisted-by tags so useless tbh and just >> pure noise in the git log _especially_ for a core developer like Jeff >> that I really don't see the point of them and I'm always tempted to just >> remove the tags when I apply. I have dropped them before because I found >> them so pointless. >> >> Crediting Jan here is the right thing to do and it provides actual value >> and also just makes sure that a real person who spent time helping out >> gets visibility in the git history. Why we should extend the same >> courtesy to automated tooling is really beyond me. Somehow we've become >> all convinced that these tools require a special status but have spent >> months arguing about the usefulness of other tags. > > To be clear, Christoph and Ritesh also contributed a lot of review and > suggestions. > > I was mainly trying to follow this new verbiage in > Documentation/process/submitting-patches.rst: > > ------------------8<------------------- > Using Assisted-by: > ------------------ > If you used any sort of advanced coding tool in the creation of your patch, > you need to acknowledge that use by adding an Assisted-by tag. Failure to > do so may impede the acceptance of your work. Please see > Documentation/process/coding-assistants.rst for details regarding the > acknowledgment of coding assistants. > ------------------8<------------------- > > If we're demanding this from anyone, then we should demand it from > everyone. I don't think we want one set of rules for core contributors > and another set for other folks. > > As to whether we should add them at all -- I don't know. I think it > really comes down to what we intend to do with this info. I'll play > devil's advocate for the moment: > > The cost of adding these tags is low. It's just a few extra bits in the > repo. Maybe this could eventually have historical value? As we don't really know "how" AI tooling helped. it's pretty useless without a more detailed description I'm afraid. OTOH, we want people (in particular not trusted community members) to indicate that it might all just be unchecked AI output. Hm. -- Cheers, David