From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 35DCB49F124 for ; Thu, 1 Oct 2026 08:08:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790842098; cv=none; b=NJEKuOihpqOVCUOH3359PIfms1qeugqyJq6bW9/P6FWhEOI/0FREB693Qeb+CUEB16aj4yLOMtXuHZwdvAoT2qEOmAorDQ0IUz9IkUo1mPOgy5nadikNkgatraEmON6+yvZ5PzipMq0yxgf8lheXsspKiihEB4gZOB+kU6ifplE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790842098; c=relaxed/simple; bh=hpxjLp0Flc1mAqfGQg6IsPkebYGUNRUGLp4GpyMsRzM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tDueU5YXk9j/I69uvTpfZPGBHK5GKhCSxcPs+Sy1t+NXryIKBkcQ4i4aHVv4ej97keKMPY/AA5vCOVgburjnMydLnS7NnT8Mj8FeXDDfdUJ4NA7gtZt8ZTqmqQJv2bYSh9SJVKKONCIJJKzHEpcKLO5hTfryzuBiWQLhsfhhDIE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TTK7DYyu; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TTK7DYyu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E8BE81F00898; Thu, 1 Oct 2026 08:08:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790842096; bh=JBoILZl5w3rVZdYCV2v/uH/WRs7MvT7FJjqh3dz2DgY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=TTK7DYyuhN9N2otVMELrHbTGkXbrOThlT22Y7LYi0nOdcFMAlHlFk6f3pekWwcF7R ou7xnpphnEv8hHBv1eP0diT7ejGGq3gUWoBnD2ZO4xgfTQGPc8t0TrD+7YaPtapy/G 2nHyNzjqBSNXC2hDTgXkSTqNGvaPXRqQqixRcuN3U87nprDU9UmLKxhp2ygzs3NZfi 2QCiaeFC27NwpdxZueJwfbbPW3LSzAhaDRsU3tPPtFheq94+zDgiHdy0OeQgZCJMV1 HrBl7Rn2ZDXexNFUETf6cQRsddZEtyg8mtAnwIsKLjAtS3q5zNzvg7kSOGUEVb/6Q0 YNnzsEAGai/zw== Message-ID: <67034af3-9849-49ab-8904-6d661178222f@kernel.org> Date: Thu, 1 Oct 2026 10:08:09 +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 v4 08/13] mm/collapse: call collapse_file() from collapse_single_pmd() To: Kiryl Shutsemau , Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang Cc: "Kiryl Shutsemau (Meta)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Jann Horn References: <20260928100630.21870-1-kirill@shutemov.name> <20260928100630.21870-9-kirill@shutemov.name> 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: <20260928100630.21870-9-kirill@shutemov.name> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/28/26 12:06, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" > > collapse_scan_file() reads the page cache to decide whether a table is > worth collapsing and, when it is, calls collapse_file() itself. The > caller cannot get between the decision and the collapse. > > Move the collapse_file() call up into collapse_single_pmd(), so the scan > stops at the decision. > > Two things change with it. The writeback retry re-runs collapse_file()> alone instead of rescanning first; collapse_file() repeats the scan's > checks under the page cache lock anyway. That change wasn't actually required for "call collapse_file() from collapse_single_pmd()", right? You merely decided to move the retry label in the same patch. > And mm_khugepaged_scan_file > fires before the collapse, so for an accepted table its status reads > SCAN_SUCCEED; what the collapse made of the table is for > mm_khugepaged_collapse_file to report. Ack. > > Preparation for splitting a collapse into a scan under mmap_lock and a > run without it. The file scan has to stop where the anonymous one will. > > Assisted-by: LLM > Signed-off-by: Kiryl Shutsemau (Meta) > --- > mm/khugepaged.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 60ec7e80d554..89a4c3f5a91c 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2737,13 +2737,9 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, > else > cc->progress += HPAGE_PMD_NR; > > - if (result == SCAN_SUCCEED) { > - if (present < HPAGE_PMD_NR - max_ptes_none) { > - result = SCAN_EXCEED_NONE_PTE; > - count_vm_event(THP_SCAN_EXCEED_NONE_PTE); > - } else { > - result = collapse_file(mm, addr, file, start, cc); > - } > + if (result == SCAN_SUCCEED && present < HPAGE_PMD_NR - max_ptes_none) { > + result = SCAN_EXCEED_NONE_PTE; > + count_vm_event(THP_SCAN_EXCEED_NONE_PTE); > } > > trace_mm_khugepaged_scan_file(mm, failed_pfn, file, present, swap, result); > @@ -2774,8 +2770,16 @@ static enum scan_result collapse_single_pmd(unsigned long addr, > > mmap_read_unlock(mm); > *lock_dropped = true; > -retry: > + > + /* > + * SCAN_PTE_MAPPED_HUGEPAGE is work too: the page cache already holds > + * the PMD folio, and only the PTE table is left to retract. > + */ > result = collapse_scan_file(mm, addr, file, pgoff, cc); > + if (result != SCAN_SUCCEED) > + goto put; > +retry: > + result = collapse_file(mm, addr, file, pgoff, cc); > > /* Dirty pages are worth a writeback and one more try, if asked for */ > if (cc->policy.file_writeback_dirty && result == SCAN_PAGE_DIRTY_OR_WRITEBACK && > @@ -2787,6 +2791,7 @@ static enum scan_result collapse_single_pmd(unsigned long addr, > triggered_wb = true; > goto retry; > } > +put: > fput(file); > > if (result == SCAN_PTE_MAPPED_HUGEPAGE) { Acked-by: David Hildenbrand (Arm) -- Cheers, David