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 A4715370D7B; Mon, 27 Apr 2026 08:06:17 +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=1777277177; cv=none; b=fcAdZYQSDcLalMMcOKHKPM/AP39hP0hdIN4JrPD8lvjepSwfE91GfL2jI5U5lV1tzijhl0M2XCurdU2b/+jXjk/7aru38VSq0Eec2pTqcZCmqRp7donjudIkc2AcTX2n/jmvsX2P9dFFxdKb0nTSNb9J06ZI2ViUk4U1wBJdrCs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777277177; c=relaxed/simple; bh=AL1E4Adq2PIOW/A91Vatqt/l1w6K52dJEV/Y71qWN1k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=c8degn/IuxIa8BmBDFzf2vjBx5JKmyiGe6TpKa1sqfOoqh3XNj09cMfw69pjtFpuFkcPT7GcuELtm/ToC54I9AYsKPGow1iDjQAcQHOhegErE9OjfnJjq8p9CtFa9aK5wt0N2eS5kajxJfDX0EjA+qPtzDliH9pCijGIpXBJnsE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=g2t8kzqx; 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="g2t8kzqx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C85CAC19425; Mon, 27 Apr 2026 08:06:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777277177; bh=AL1E4Adq2PIOW/A91Vatqt/l1w6K52dJEV/Y71qWN1k=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=g2t8kzqx8vmMdRBX237gzVsvhp4YeQG0hyJwqWNhyD+BNaIu2JVhl8NgGt2/VuzEy DYsRObdR2R/37JaVsGF6XFQjkcaJ6kgXM8VDIvx8g87a0uYkR8GTAFbxuP2xgFDaj0 TyFJRyuIsZ9bYcr1jLzPfJqMI5hnuQe4xC+1c2wV/ZEIeIgWFwFFeInviigGghXnki +dUR6jU7l9dR3CONroIcNwg6NF7K1oZ1NwvjSDIb1aZSmx32bnSXkgHxlr1yT4aUeq BV+sQ1qlzjf/58IV8br2f3kpBpf+NpO/6iGUicKamkSoA2WjWzq6eLwx9lHmG6RjcT 937RrvkSaOT0g== Message-ID: <4899bbfa-4d6e-41ff-9318-1872a6b91afa@kernel.org> Date: Mon, 27 Apr 2026 10:06:06 +0200 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 7.2 v3 03/12] mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled() To: Zi Yan , "Matthew Wilcox (Oracle)" , Lorenzo Stoakes Cc: Song Liu , Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20260418024429.4055056-1-ziy@nvidia.com> <20260418024429.4055056-4-ziy@nvidia.com> <74D4C50B-CB20-45B3-8E7E-E9A499701F61@nvidia.com> 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: <74D4C50B-CB20-45B3-8E7E-E9A499701F61@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/25/26 14:00, Zi Yan wrote: > On 17 Apr 2026, at 22:44, Zi Yan wrote: > >> Replace it with a check on the max folio order of the file's address space >> mapping, making sure PMD THP is supported. Also remove the read-only fd >> check, since collapse_file() now makes sure all to-be-collapsed folios are >> clean and the created PMD file THP can be handled by FSes properly. >> >> Signed-off-by: Zi Yan >> --- >> mm/huge_memory.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 970e077019b7..7e9cf8c0985f 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -86,9 +86,6 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma) >> { >> struct inode *inode; >> >> - if (!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS)) >> - return false; >> - >> if (!vma->vm_file) >> return false; >> >> @@ -97,7 +94,10 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma) >> if (IS_ANON_FILE(inode)) >> return false; >> >> - return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); > > Hi Matthew, David, and Lorenzo, > > After some discussions on irc, I feel that we probably should not allow > read-write fd for PMD THP collapse at the moment. Combining with the > filemap_flush() under folio_dirty() check from collapse_file(), khugepaged > would become a kwritebackd that scans pagecache folios and writes them back. > If we limit it to read-only fds, at least khugepaged would only write > back once for the pagecache folios from these fds. Makes sense. The comment above the filemap_flush() is valuable :) > > I am planning to restore inode_is_open_for_write() check in the next version. > Let me know your thoughts. That would be better. Do we plan on handling races with concurrent writable-opening? Or could we simply gate the filemap_flush() by a inode_is_open_for_write(), to not have it turn into a kwritebackd()? -- Cheers, David