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 65AFC3B47FB for ; Fri, 17 Apr 2026 09:21:14 +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=1776417674; cv=none; b=m160TarWoZJjHSm869sKkIVvl3QkaGHeKygXUu/yzC+AIzOLUz3FO61L8BtgioONxBcXwsf9IV8QfVtsUiOSHumqDCxAaymCFMlmdmJGHbzHE5wWga49KzJbmWY5/388HPXpLln5dCfODQmOZOnYX4XgPlsS23rBj+PoVpdYVtY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776417674; c=relaxed/simple; bh=V2RFZAnMgXF+jaCr3USxaHS2Sm7HIfxBEIFGnLB1dN8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iftmqcMekrfH10iR9+EqkbHdhRfszTRwwkXpmR7yQ6Ziaay0LVLSOvQrUWB+Dbph/86zTtVWbsZk3jOB7PctOaVNbbNOK/vMDM6aChXKFngmQibWeRTc+0+PYKdneqkY9iOrDxhPZQsRO6p2Pq6Zdr4dHEMBoBKA8PhZ8c02k7Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iXCfHYYn; 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="iXCfHYYn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F6DEC19425; Fri, 17 Apr 2026 09:21:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776417673; bh=V2RFZAnMgXF+jaCr3USxaHS2Sm7HIfxBEIFGnLB1dN8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iXCfHYYnnyj9s6NhCcO7l7gl/cumQK4oF3UIrfgzRXj7adqBckWo7XULrVRZqzznf Gq67blHvotz405eP/y1zdXhVY/nOysIjtVy3ZSKf2SoHoxAEQOIXZGxXio/1iG3JFR HMdZRFlOuVXwvyPRRL3o3XQ/Q5wqwl7/ThCW+pGT7T46qHrrly1AHSu/JArluYqQrb XxZmA77/3H0YRfR4d1dwpGYqiy1tN3+epSP++AKUAyovNVI5PI/axFTTg+HBE3rXqC ePqVyC8DgYjz0p968RbcZ8Qi1Ago5TDCc2vNnYf3Etgv+7NQpwO4IrWJHBEf7HXuiO 7lKuAZ3JUH8Qw== Message-ID: <1b3c0401-6d10-4a28-97c8-8e3858d8dc3d@kernel.org> Date: Fri, 17 Apr 2026 11:21:08 +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 v3] mm: shmem: always support large folios for internal shmem mount To: Baolin Wang , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, ziy@nvidia.com, ljs@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <26f954be62348591e720c4e8b7a9099b74dc1d6d.1776331555.git.baolin.wang@linux.alibaba.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: <26f954be62348591e720c4e8b7a9099b74dc1d6d.1776331555.git.baolin.wang@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/17/26 05:25, Baolin Wang wrote: > Currently, when shmem mounts are initialized, they only use 'sbinfo->huge' to > determine whether the shmem mount supports large folios. However, for anonymous > shmem, whether it supports large folios can be dynamically configured via sysfs > interfaces, so setting or not setting mapping_set_large_folios() during initialization > cannot accurately reflect whether anonymous shmem actually supports large folios, > which has already caused some confusion[1]. > > As discussed with David[2], for anonymous shmem we can treat it as always potentially > having large folios. Therefore, always support large folios for the internal shmem > mount (e.g., anonymous shmem), and which large order allocations are allowed can be > configured dynamically via the 'shmem_enabled' interfaces. > > [1] https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/ > [2] https://lore.kernel.org/all/875dc63b-0cd2-49e5-8b0d-3fb062789813@kernel.org/ > Signed-off-by: Baolin Wang > --- > Changes from v2: > - Always support large folios for internal shmem mount, per David. > Changes from v1: > - Update the comments and commit message, per Lance. > --- > mm/shmem.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 4ecefe02881d..769ef37b1ea9 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3088,8 +3088,17 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap, > if (sbinfo->noswap) > mapping_set_unevictable(inode->i_mapping); > > - /* Don't consider 'deny' for emergencies and 'force' for testing */ > - if (sbinfo->huge) > + /* > + * Always support large folios for the internal shmem mount (e.g., > + * anonymous shmem), and which large order allocations are allowed > + * can be configured dynamically via the 'shmem_enabled' interfaces. > + * > + * For tmpfs, honour the 'huge=' mount option to determine whether > + * large folios are supported. > + * > + * Note: don't consider 'deny' for emergencies and 'force' for testing. > + */ > + if (sbinfo->huge || (sb->s_flags & SB_KERNMOUNT)) > mapping_set_large_folios(inode->i_mapping); Two questions from a non-fs person about the semantics here: a) Can sbinfo->huge be triggered later, for example, through a remount (staring at shmem_reconfigure()) b) Do we cover all cases with the SB_KERNMOUNT where sbinfo->huge cannot be changed later? -- Cheers, David