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 A38FD26C385; Thu, 6 Aug 2026 13:56:47 +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=1786024608; cv=none; b=noc3ao946806NtqbzIpcFQ9CC87f0WVH7lfl9hK4lZEeIiiXTXAebM6TQNgp1W5N/4Y9lwvs1vgGy0aH9Zc7CVIqJthe6NRQF6DkcMwabyQEQ2spBdz8XPBTAPjdmutGS63TQTRzwdrXF134xRuYxJi0uah8iRCeN4lo1EXRWwk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786024608; c=relaxed/simple; bh=ALY136eq9o3kgQ4G/vDF4wYJGUl/aKk6s2or5AVblv0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NFVjll23bbQG7lFZ5LlgbHyq1pWVMEsLjoJx6BszviKkyhuligj+AeuF+nHI/c1WOooQYmtKfmI5Al0vTJ6F/K+Nd1wTsC9pzIr1Qa70qYox1Z3lwnoemiWSCcGGUJpP0oKeX8D0vM1Pm0o/C08X97WeBCLSk64thQ4gwfsUbcs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DkGAyZHD; 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="DkGAyZHD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2DC41F000E9; Thu, 6 Aug 2026 13:56:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786024607; bh=MC7T7ylhK/aLr9fs0E5SYbo5bCKm86oRgZDfYL13AS4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=DkGAyZHDVpHpzU+8ZKASQVokbVrEOI2Cii14k622zjZ3cwd+Ne0Csvoj1YN6XENG2 H6pM+hFjLX144QIABtWKyQNdmRNlQqAo9KOZsuVMgPVI2HU+aYeTA9WBkxKJNTvsxl 7lZChMbTyMO+ZcnZwpoSJDoGdnUcZbnQkAzLD6/tOGHXr0yGNSzKAn6ZkDwDMKs0a8 0AR97NvqqDYbqVSd9DbVAOHVoj5q22bDD3m9UmUPN2nRhjMnbqYVKcDVrVMGzfrL1D yQUySxekwYv0qd9PjbpnVJzwEnJ7+7UZ1Avixh4y/xFPoppigmWx1aOBhr/5xfa9vZ Fxwf+avkzMfBQ== Message-ID: <77a27056-555e-4395-b71e-e777548750e0@kernel.org> Date: Thu, 6 Aug 2026 15:56:35 +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: [RFC PATCH v5 2/4] mm: distinguish large folio swap allocation failures To: Xueyuan Chen , akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, zhaonanzhe@xiaomi.com, baohua@kernel.org, hannes@cmpxchg.org, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, hughd@google.com, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, baoquan.he@linux.dev, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, qi.zheng@linux.dev, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com References: <20260730122304.2496440-1-xueyuan.chen21@gmail.com> <20260730122304.2496440-3-xueyuan.chen21@gmail.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: <20260730122304.2496440-3-xueyuan.chen21@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/30/26 14:23, Xueyuan Chen wrote: > folio_alloc_swap() reports most allocation failures with a generic > negative error code. Reclaim cannot tell whether splitting a large folio > could make progress or whether there is no backing space at all. > > Keep the global free swap count and the remaining hierarchical memcg swap > margin as separate inputs. The memcg charge path reports only its own > margin; folio_alloc_swap() combines the two layers when classifying an > allocation failure. > > Return -E2BIG for large folios when a smaller allocation might still fit, > -ENOSPC when no global swap space is available, and -ENOMEM when the > failure is not helped by splitting. > > For early large-folio rejections, check global and memcg swap availability > instead of returning -E2BIG unconditionally. On a memcg charge failure, > swap slot allocation has already succeeded, so use the remaining memcg > margin to decide whether a smaller charge might fit. > > This only refines folio_alloc_swap() return codes. The reclaim callers are > updated separately. > > Suggested-by: Barry Song > Suggested-by: Youngjun Park > Signed-off-by: Xueyuan Chen > --- > include/linux/swap.h | 16 ++++++++++++---- > mm/memcontrol.c | 32 +++++++++++++++++++++++++++++++- > mm/swapfile.c | 32 ++++++++++++++++++++++++-------- > 3 files changed, 67 insertions(+), 13 deletions(-) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 0544b2ec4c56..7d12058174ae 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -509,12 +509,13 @@ static inline void folio_throttle_swaprate(struct folio *folio, gfp_t gfp) > #endif > > #if defined(CONFIG_MEMCG) && defined(CONFIG_SWAP) > -int __mem_cgroup_try_charge_swap(struct folio *folio); > -static inline int mem_cgroup_try_charge_swap(struct folio *folio) > +int __mem_cgroup_try_charge_swap(struct folio *folio, long *swap_margin); > +static inline int mem_cgroup_try_charge_swap(struct folio *folio, > + long *swap_margin) Nit: two tab indent [...] > -static inline int mem_cgroup_try_charge_swap(struct folio *folio) > +static inline int mem_cgroup_try_charge_swap(struct folio *folio, > + long *swap_margin) Nothing else jumped at me Acked-by: David Hildenbrand (Arm) -- Cheers, David