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 303AC13A86C; Fri, 8 May 2026 19:40:08 +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=1778269209; cv=none; b=NILF9zDJHUWKdddZkzYvo72kdn32kQS27gzfyGEqsKmlmsEnx0gvxhqqtwTlUtdYVD2TSdAVe3yNkaBZ5dxyO83+cKTOdvQGjaq5ro9FEO+mvRGeTkPeGPuPPyDrYVxQKd31a8/MuJTxg039neW/qjYq5wggn2eAp+s0ngHszEo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778269209; c=relaxed/simple; bh=bEvGjngPqBRZCRr5j8qzVVNl7z2K7O10AOSptjW9O80=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KKE2q6SZR+WPayBv3RPYExUVhTdo/hpOvVT3S5XWeKUUSO8Nw/dR2/GtfnWljQVGberhsAljNPm1jiu0xteV7C9Y7YqKHkYLfGC641mSBEUuVh9kx4NwHV0MibwoNWaBozKrPr7m3+bjnlj/o9g14zQlrmlIP/U02X4Qy6vV3eQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SBQl+v1b; 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="SBQl+v1b" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8E9CC2BCB0; Fri, 8 May 2026 19:40:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778269208; bh=bEvGjngPqBRZCRr5j8qzVVNl7z2K7O10AOSptjW9O80=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=SBQl+v1bR7jR2dnGJULf2Jju99Rm/OtQ0W4c8kKHsUGraUwF4B5mXIRHRN5421WyY 8Zw9o3blCEjNi9rqBlfGkx/6V/AHiDYhNZ3HiEmvYBUD5lhK89eOTldXPW5Z3jy9tz Qs8xSIZUersqClg5HRXkl3yYOmZV4rCKUiTAIwEq67EtQzKzJEfBsUrnDOol4lTxfq XCiiwTcwSYkxnGbu8R5ykiFfxnvOzk221t4U0lL6YNXvilYJekcUSHd2I691A0j3A2 tTSdvTYtb0KVCBkYZe01wq5nBd04/Szq3gjTRFkOfUWeRUUday7DpZn9xYHN2na3aj tivyvj0NJhQMw== Message-ID: Date: Fri, 8 May 2026 21:39:56 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 01/14] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check To: Zi Yan , Andrew Morton , "Matthew Wilcox (Oracle)" , Song Liu Cc: Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Lorenzo Stoakes , 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: <20260429152924.727124-1-ziy@nvidia.com> <20260429152924.727124-2-ziy@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: <20260429152924.727124-2-ziy@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/29/26 17:29, Zi Yan wrote: > collapse_file() requires FSes supporting large folio with at least > PMD_ORDER, so replace the READ_ONLY_THP_FOR_FS check with that. > MADV_COLLAPSE ignores shmem huge config, so exclude the check for shmem. > > While at it, replace VM_BUG_ON with VM_WARN_ON_ONCE. > > Add a helper function mapping_pmd_folio_support() for FSes supporting large > folio with at least PMD_ORDER. > > Signed-off-by: Zi Yan > Reviewed-by: Lance Yang > Reviewed-by: Baolin Wang > --- > include/linux/pagemap.h | 26 ++++++++++++++++++++++++++ > mm/khugepaged.c | 10 ++++++++-- > 2 files changed, 34 insertions(+), 2 deletions(-) > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index 1f50991b43e3b..1fed3414fe9b8 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -513,6 +513,32 @@ static inline bool mapping_large_folio_support(const struct address_space *mappi > return mapping_max_folio_order(mapping) > 0; > } Some smaller doc improvements: > > +/** > + * mapping_pmd_folio_support() - Check if a mapping support PMD-sized folio "supports" > + * @mapping: The address_space > + * > + * Some file supports large folio but does not support as large as PMD order. "While some mappings support large folios, they might not support PMD-sized folios." > + * If a PMD-sized pagecache folio is attempted to be created on a filesystem, > + * this check needs to be performed first. I'd rather just add (relate to the previous sentence): "This function checks whether a mapping supports PMD-sized folios. For example, khugepaged needs this information before attempting to collapsing THPs". > + * > + * Return: true - PMD-sized folio is supported, false - PMD-sized folio is not > + * supported. I'd say "folios are supported" and end up with: "True if PMD-sized folios are supported, otherwise false." > + */ > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +static inline bool mapping_pmd_folio_support(const struct address_space *mapping) > +{ > + /* AS_FOLIO_ORDER is only reasonable for pagecache folios */ > + VM_WARN_ON_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON); > + > + return mapping_max_folio_order(mapping) >= PMD_ORDER; Agreed that this should check for ==, although in practice it would currently not make a difference. > +} > +#else > +static inline bool mapping_pmd_folio_support(const struct address_space *mapping) > +{ > + return false; > +} > +#endif > + > /* Return the maximum folio size for this pagecache mapping, in bytes. */ > static inline size_t mapping_max_folio_size(const struct address_space *mapping) > { > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index e112525c4aa9c..6808f2b48d864 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2235,8 +2235,14 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, > int nr_none = 0; > bool is_shmem = shmem_file(file); > > - VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); > - VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); > + /* > + * MADV_COLLAPSE ignores shmem huge config, so do not check shmem > + * > + * TODO: once shmem always calls mapping_set_large_folios() on its > + * mapping, the shmem check can be removed. > + */ TODO LGTM. Acked-by: David Hildenbrand (Arm) -- Cheers, David