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 8BD6B42A16F; Mon, 27 Jul 2026 17:31:09 +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=1785173472; cv=none; b=RXQX/BoBpKVYGuSTkc9rWDwxyXiSeb35Fy+buQ7DDFvLpDxACuyGWp28xlXxgYDk9fTyphe/qsiLOsT5Loen9jNf9XOwLiW6luKR6qqCSgF+pTdmzTZEVuwH+Aey77F/t2A8rp/mx0lEM5V4rvMpk6VOjIPtwDo10BMPO0Hgnuk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785173472; c=relaxed/simple; bh=BGELpQYwYkawAqcdG6LRscN06nOv2YpKhru4YQQ/Zcw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S7Y91BjRgqcA0mleDBo5q9ytrFrGQGevjKxuftREglA2dG9fbrr7jwEL97qFl5yKg7D4H8C2H7P+DkcInNWxzwhrIyEPG8RDbek/vl5RyQm2xgeRAUYsSLClT3vnhQwWMjhe6iycx49AQjRXxUhSa1RF4aUoVOwdbpHqJ67dJ4Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Tgcp/6d+; 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="Tgcp/6d+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 827011F00A3A; Mon, 27 Jul 2026 17:31:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785173468; bh=FeuJKdYUaVLKNBfWUd4HTmd0q5nfx0zD3ldduTDAYyw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Tgcp/6d+oehw4jDZPMJxHA7W9qn4aC2gFYD7gy9EXODmJCAyFVQTa1rPfhqeWoew5 Y8D3kgRBHTLk8wRpNYx/lh/CJbi9sGnokVUwUQcjUwKia/o3MlNovgq0U9Sh5CJHdI S8vOrgAm+++TF5TjAp5Hylm17hxvbJBCRIWLYu2WlswQBrM/V2YCFIV9w1shQ1cyNm i6Egn5y0+toxfqtOSQmy64WdvsRNkBL/4490Kow5eZLM+InHbK5a4m/fSsLu49so0U kg402vDz5qjt3yEK3UvSg4nWOo8QBL4Srr1UqNxjCR6cOBIbNGWTvr53xdyCSRuMKZ QztiFaMubtRnQ== Message-ID: <312caaf8-1661-4437-aaac-a93bf701ccf9@kernel.org> Date: Mon, 27 Jul 2026 19:30:58 +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] mm/huge_memory: Initialise workingset state before folio split To: Matt Fleming , Andrew Morton Cc: Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Dave Chinner , Qi Zheng , Roman Gushchin , Muchun Song , Kairui Song , Shakeel Butt , Matthew Wilcox , syzbot+c5b060ce82921a2fd500@syzkaller.appspotmail.com, stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@cloudflare.com, Matt Fleming References: <20260725101419.3938406-1-matt@readmodwrite.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: <20260725101419.3938406-1-matt@readmodwrite.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/25/26 12:14, Matt Fleming wrote: > From: Matt Fleming > > xas_try_split() adds __GFP_ACCOUNT for page-cache xa_nodes, but > __folio_split() leaves the xa_state's xa_lru unset. That lets a live, > memcg-charged xa_node exist without being linked into the mapping's > shadow_nodes list_lru; when reclaim later walks the list_lru it trips > VM_WARN_ON(!css_is_dying()). > > Use mapping_set_update() to install both the workingset update callback > and the shadow_nodes list_lru on the xa_state. > > Reported-by: syzbot+c5b060ce82921a2fd500@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=c5b060ce82921a2fd500 > Fixes: 58729c04cf10 ("mm/huge_memory: add buddy allocator like (non-uniform) folio_split()") > Cc: stable@vger.kernel.org > Reviewed-by: Zi Yan > Signed-off-by: Matt Fleming > --- > Changes in v2: > - Move mapping_set_update() after filemap_release_folio() succeeds. > - Add Zi Yan's Reviewed-by. > > Link: https://lore.kernel.org/linux-mm/20260724195244.3715130-1-matt@readmodwrite.com/ > --- > mm/huge_memory.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index b5d1e9d4463d..4ddbc72e92fd 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -4033,7 +4033,7 @@ static int __folio_split(struct folio *folio, unsigned int new_order, > gfp_t gfp; > > mapping = folio->mapping; > - min_order = mapping_min_folio_order(folio->mapping); > + min_order = mapping_min_folio_order(mapping); > if (new_order < min_order) { > ret = -EINVAL; > goto out; > @@ -4047,6 +4047,8 @@ static int __folio_split(struct folio *folio, unsigned int new_order, > goto out; > } > > + mapping_set_update(&xas, mapping); > + It's entirely unclear when mapping_set_update() should/must be called. ... or even what it does. Why is it called "mapping_set_*" when, in fact, we modify the xas? The more I look at it, the more angry it makes me :) Can someone please try finding a better way to handle this? E.g., can we somehow remember in the xarray that we have !dax_mapping(mapping) && !shmem_mapping(mapping) early, and just do the right thing from xas code? Or is there some way we could have a mixture in the same xarray? Anyhow, for this patch here, I guess it's fine. I am convinced nobody can say that with confidence. Black magic. Acked-by: David Hildenbrand (Arm) -- Cheers, David