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 A4515428470 for ; Mon, 7 Sep 2026 11:51:25 +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=1788781886; cv=none; b=WSNU7O23cHzbpGgdbduD7IESIOL04hYw9U8WBwjlug4gaPlRkJxeL04Uh7Ro3pKC3iRJgCbjNb5ru+VW/s+/d3rme29qlBdQUMnfhckS6L0ZYjTMjOW9LG89LB+cHjQNkqkU1Q/ETibv09/1FJcPJodW9aSS5+1IcVlMa0wUEZo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788781886; c=relaxed/simple; bh=Rjdejn2cy5T5pLK3/p8C9NOeImQlLOQN3oGgciig5Wg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jTclNoE3UyQhFiAwoUEHIv/2uIwAAuJb0Y+Wk91eVPmiB/W0AdEKVr0G4vF5SH5Hzwp+RdNt3QoEfBNZVQ31RM/b8tz6jWDFDyfAzN111GJWhaunHTPALJTQiTOBC/PV+2vMZDOTvacMTguxQ16ahdM9JH3cQ7E/4KgLZ410Txs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nHSF+NiD; 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="nHSF+NiD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A96911F00A3A; Mon, 7 Sep 2026 11:51:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788781885; bh=y+aPhc/SqhJ7JSMC3ivXbbYiLBKgxE4zPMSB4aVyP+8=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=nHSF+NiD6uq7sSUj9YDZ36amjTyArKCHbqydgbhqrn7tOJpTXs1l04YLotUgTb0hO Ckhkl66Bqh9dJutppBBoVi6eA3IkONRUlRoOJapdpZtJorG5PFfwnggyU1u2W9rrgk CjkjBiP2I4Gp88q43O04If5BhwBZHoM9abcQpRSON/ZRVxLrmgLOub7baaxvz4NFmN MSJnNgxhU7iUwBAhlBuhsiBQWwMUFGCxLAl278BiyIa9q6EEfB69LerlaLQn4AFN/E KDG/V7ZSYcJq8MSe9RW3Z0SDC4pGGZC0XjkvhVzirwdNcy4JbYjiXqWkFq3ecDCUTi ISujGXYthbxPA== Message-ID: <5930324d-8252-42e1-ad50-aab796e41550@kernel.org> Date: Mon, 7 Sep 2026 13:51:20 +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] mm/madvise: swap in CoW'd MAP_PRIVATE-file mappings on MADV_WILLNEED To: "Lorenzo Stoakes (ARM)" , Pedro Falcato Cc: Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mike Kaplinskiy , zhaozhengzhuo References: <20260904-madv-will-need-map-private-v1-1-6b83cc99fcff@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit > And it's a real improvement to have unfaulted anon skip... > > But I find that version is documenting what's going on a lot less. > > Since both anon and MAP_PRIVATE file-backed are CoW mappings we could just > reference that. > > Andrew - could you swap the patch out in-place with below? Thanks! A proper v2 would have been nice ;) (and would trigger sashiko and friends properly) > > Cheers, Lorenzo > > ----8<---- > From a706374a1186b6b4409a0e760e8728bcadba0c96 Mon Sep 17 00:00:00 2001 > From: "Lorenzo Stoakes (ARM)" > Date: Thu, 3 Sep 2026 20:08:39 +0100 > Subject: [PATCH] mm/madvise: swap in CoW'd MAP_PRIVATE-file mappings on > MADV_WILLNEED > > Currently MADV_WILLNEED treats file-backed and pure anonymous mappings > entirely separately - using POSIX_FADV_WILLNEED (equivalent of a readahead) > for the former and a tree walk and swap in to swap cache for the latter. > > MAP_PRIVATE-file backed mappings straddle the two and currently get treated > as if they were purely file-backed, meaning any swapped out private pages > remain swapped out. > > Resolve the issue by explicitly checking for CoW'd MAP_PRIVATE-file backed > mappings and performing both walks in this case. > > Since the logic checks for vma->anon_vma this means un-CoW'd > MAP_PRIVATE-file backed mappings retain only the single file walk. > > Reported-by: Mike Kaplinskiy > Closes: https://lore.kernel.org/all/CABeknB_S2XJSHFgnHdgnN0rjzHhH4oQJs_APq9fvxHztQ_pgiA@mail.gmail.com/ > Signed-off-by: Lorenzo Stoakes (ARM) > --- > mm/madvise.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 73c2901b9adb..963337f93a7a 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -297,11 +297,12 @@ static long madvise_willneed(struct madvise_behavior *madv_behavior) > loff_t offset; > > #ifdef CONFIG_SWAP > - if (!file) { > + if (vma_is_cow_mapping(vma) && vma->anon_vma) { > walk_page_range_vma(vma, start, end, &swapin_walk_ops, vma); > lru_add_drain(); /* Push any new pages onto the LRU now */ > - return 0; > } > + if (!file) > + return 0; > LGTM Acked-by: David Hildenbrand (Arm) -- Cheers, David