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 224BE46A5EC for ; Fri, 21 Aug 2026 09:58:55 +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=1787306342; cv=none; b=XxcuUIVqVxp5ThFbHn/l3km5HFAVTiO6okyogBksVqEh6DTfBpErt6t4enB/4z+ufDQBX0qg2nNvX4X4t4TLo3fX9sNUReha8SvlLudl3uwM0X8QrsFcoYfqdfFnKKqoAScNiAsSE2h3xVYLz5T2VJljpBcu5f94PddmUdoGmQY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787306342; c=relaxed/simple; bh=0vuCD3Ho6L4NMJFmwthHLN7toaENLIimuwpE9S1IU5k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ON8NENo94anxe0D9R5c9TdMa/YfyPUqNYW0thUBCMpFts6JCElpsmOAqASg+rPwEA9tGFGqO8Z91UtuvlKCugPcDjgyQQLnembtPasyCTFIlsVB/dLo0B9pO1V1hoYwm3k5NxHAijRS4/QUKnCU5sn84k1MwkyXOmV/SPSVzH9E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cHF2KKX3; 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="cHF2KKX3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B8851F000E9; Fri, 21 Aug 2026 09:58:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787306331; bh=vOBFFN3DogCz6H5/khZbeZaJY/DvAhpaGbrZVIDS07E=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=cHF2KKX3gX0wJna0xdHDX/lXXUaFtDwFPYOdtTYGJ/dTz06ZcMf0qutw0drcSZfkz UO1heuB6gInCl8NFG5BCE8TEcBPM69yEaQWqPZtVNVA5R6VGkQ83KHLoSXBBvwz5Cu xpN1OpNUTo107yf8ioy6M386UyIbwZDU327W66ktwVdY/2PdNo0q6fabHJ7aG6vR2l EIPhBcthZVVwatmeJh/S/p51d21jt+5pR1o97t/ZulFIS5/i+1IFvfyDjD7sYlIPgz ytOIfLtxBztkuT7tlN1T4+0+B5sSWbS+dvsTYBOa0aPIn96Pklbjr7kk+2c0goi3QE kgF0k9SFII+gA== Message-ID: Date: Fri, 21 Aug 2026 11:58:43 +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 v2 3/3] mm/zswap: preserve the workingset shadow across writeback To: Alexandre Ghiti , Johannes Weiner , Yosry Ahmed , Nhat Pham , Chengming Zhou , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Hugh Dickins , Baolin Wang , Chris Li , Kairui Song , Kemeng Shi , Baoquan He , Barry Song , Youngjun Park , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , Joonsoo Kim Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260821093606.2231216-1-alex@ghiti.fr> <20260821093606.2231216-4-alex@ghiti.fr> 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: <20260821093606.2231216-4-alex@ghiti.fr> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/21/26 11:35, Alexandre Ghiti wrote: > When zswap writes an entry back, allocating the buffer folio in the swap > cache overwrites the swap slot's workingset shadow. It is lost and later > re-minted inaccurately, which corrupts anon refault/workingset accounting > for the written-back data. > > Preserve it within zswap itself: at writeback, park the shadow in the > zswap tree in place of the freed entry, so it outlives the writeback > buffer folio. The buffer then meets one of three fates, and the parked > shadow is handled at whichever happens first: > > - swap-in: do_swap_page()/shmem_swapin_folio() find the buffer in the swap > cache, take the shadow and feed it to workingset_refault() to account > the refault of the now-resident folio, then drop it. > - reclaim: __remove_mapping() skips minting a fresh shadow for the buffer > (minting would double-count the eviction) and > __swap_cache_do_del_folio() restores the parked shadow into the slot, so > a later disk swap-in still refaults against the original eviction. > - slot free (e.g. process exit): the shadow is not needed and is cleared. > > The last two both go through __swap_cache_do_del_folio(), the single point > every swap-cache removal passes through, which is why the shadow is read > and cleared there. > > Fixes: aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU") > Signed-off-by: Nhat Pham > Signed-off-by: Alexandre Ghiti > --- > include/linux/swap.h | 2 +- > include/linux/zswap.h | 12 ++++++ > mm/filemap.c | 2 +- > mm/memory.c | 5 +++ > mm/shmem.c | 5 +++ > mm/swap_state.c | 14 ++++++- > mm/vmscan.c | 4 +- > mm/workingset.c | 16 ++++++-- > mm/zswap.c | 91 ++++++++++++++++++++++++++++++++++++++++++- > 9 files changed, 142 insertions(+), 9 deletions(-) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 6d72778e6cc3..ef9b1612ac12 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -298,7 +298,7 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset, > bool flush); > void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages); > void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg); > -void workingset_refault(struct folio *folio, void *shadow); > +void workingset_refault(struct folio *folio, void *shadow, bool lru_managed); Passing booleans makes calling code hard to read. It's preferable to either use (a) Dedicated flags; only makes sense if there are really more flags expected (b) Having helpfer functions that spell it out for calling code workingset_refault_lru_managed workingset_refault workingset_refault_lru workingset_refault_nonlru Or something like that, which makes calling code easier to get. -- Cheers, David