From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DF2AEC83000 for ; Tue, 24 Jun 2025 19:54:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=3sH2p7wTC5c2K+AMt4asivtrMKZsRfHnk0S9o2dg5hU=; b=UKAW0p6FVn4ZhG ItGYf3ow2FY9kjhyD8UkbbBaBdWbQiUbO3dKnqaiOZ0f63hYOYqB3ZFqmxMJJoQSo6fOgkNcA3VRI nmEd3BsImlHnBiizf1TcoY4wcdC7zDJo//CuLjLA7Z0WEJA3+W/xvVrlGYC6Lww7Nnt7oM3Qy5GJz oLDAfwhf8Z01kVUI5rACppoHo8o20OIROaXOgsu7p3uDsbjh2xPYJSn0HeNL0vu1jtaa7nPZQ/p0X cH9kD1MPvc001zpLrX1cwcg2dCoKueKW4egluszlcgYooS/7HiMiwor0xBCUyn4BnYGzs5knc4p2w FiJxEEmf6JpU0jWuwi7g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uU9iz-00000006fBO-1opw; Tue, 24 Jun 2025 19:54:33 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uU5fI-000000068P3-43xf for linux-riscv@lists.infradead.org; Tue, 24 Jun 2025 15:34:30 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1750779268; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=RcLpQIGOHnObqeC9JE4WrzqVitzt8nhGtyf8y+j3oKs=; b=YYjOhwuB8unigFceDLIc9+Jk7cuifrVmySXAe2FrVC9YA0m98BufvgroDj0JaaeuvHFLHC 31Sb1EMIi8BgRYGOsehq3MJk8rZmiv1wIEKlabz4K8vTFvGa3526H6+T1mTK7p1IF5DbBa jcPKeefJpBUFE4yCC490dcI247cQet0= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-590-lw0oR7fWM52_NlH-d9QpwQ-1; Tue, 24 Jun 2025 11:34:26 -0400 X-MC-Unique: lw0oR7fWM52_NlH-d9QpwQ-1 X-Mimecast-MFC-AGG-ID: lw0oR7fWM52_NlH-d9QpwQ_1750779265 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-3a4eb6fcd88so2799214f8f.1 for ; Tue, 24 Jun 2025 08:34:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750779265; x=1751384065; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=RcLpQIGOHnObqeC9JE4WrzqVitzt8nhGtyf8y+j3oKs=; b=XmnZyKfOIbWe2ZVsggXbpICehPzdIaOHZmZUA2Yp7/Fz+MWfVQ2myRjNkq9oCGJw15 o0rtIrok2vpj/Kpshna3m6zThLeJmJok/+i0pU8ycEYBBvUiVTkq2q4qYidiqjh3TIU7 gWABHoM0+5SH9sC5xYDO4PGTUmppakW4tHh4Yw/tYmS9jHSDeQbvoOWg7o4WIgVYyxwg FuBV6d1FRKEn8CxPCPWA3jpkN5yoq3RcthJt5VO6DO2g7MLaU51SPqfe2rK+8fx0EGIv 6qsbSXw04UiCDvdr4u8loW7UuKkK2FEBzOn12unVo00jszErOJCSDl5pEohCnJ2dZGu/ ml0Q== X-Forwarded-Encrypted: i=1; AJvYcCWt8tQHAcBMtWv6Zy1x6zCTsEOQ5CThq4b28UqlXd7rdpI1q01qR5oD3ytm9oZiEtRRFwkE3AjYoXnW0A==@lists.infradead.org X-Gm-Message-State: AOJu0YwIuoAyJhQtJN3rVnXKHAV4mmFRoY5RD0f0wwcPlV+ntt/t1vq/ JdgHcWMB+GzNHcH4iOzw4tJnBnu06+NkoMvINaDOmTPJhyv0wRjp8fCZST+3eNPBLUzQHdrPbjp 8/DcyDEqv95UG5MscMOs3XNAfGBgD4XJbSs6QIgjK+FzI950U0qKPNIA/StYfXU2461+xLA== X-Gm-Gg: ASbGncst+VpcWaH5sgQQIFRgi8Ur4afFdMTQ4L+aAuFNUxCfJOZWhTD7mUiyMn+sPfI UtrtePeU8zdo8xyyS73v9mmZnRMHX9u2JQe/xY9QzdAkJPq6ad2IQYKyZJXCv0kVNe4wb6qomEF hRJRWTqnAxIdfME+2oTU1CuI0uKr69/5UJoFQlCbypxdRr/NRp6qyzaYNehpaS/LiJb7nj3RCda aTfgA756OIn0d3ZHZ4/mIrQa1XqAKj6tfObV453S7XfnZnPHkrQz6gxcKSR1rh9l8dMItB84FWl 53VamFmd7cKkveSO7jP3PZb1qCgSK08X/4ZcvAA6OujuWekcUl8N7is= X-Received: by 2002:a05:6000:644:b0:3a1:fa6c:4735 with SMTP id ffacd0b85a97d-3a6d12de9f5mr15286845f8f.35.1750779265347; Tue, 24 Jun 2025 08:34:25 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH6Ygv2yKeSOnyksLf8xOR4yHKXMKNiKsSWotC4sSpeb23NQbCgX43VhwnxwPvnUhGhaM9S2Q== X-Received: by 2002:a05:6000:644:b0:3a1:fa6c:4735 with SMTP id ffacd0b85a97d-3a6d12de9f5mr15286806f8f.35.1750779264907; Tue, 24 Jun 2025 08:34:24 -0700 (PDT) Received: from ?IPV6:2a09:80c0:192:0:5dac:bf3d:c41:c3e7? ([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-453755e7d1dsm62924635e9.10.2025.06.24.08.34.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Jun 2025 08:34:24 -0700 (PDT) Message-ID: <2c19a6cf-0b42-477b-a672-ed8c1edd4267@redhat.com> Date: Tue, 24 Jun 2025 17:34:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/4] mm: Support batched unmap for lazyfree large folios during reclamation To: Lance Yang Cc: 21cnbao@gmail.com, akpm@linux-foundation.org, baolin.wang@linux.alibaba.com, chrisl@kernel.org, kasong@tencent.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, v-songbaohua@oppo.com, x86@kernel.org, ying.huang@intel.com, zhengtangquan@oppo.com References: <20250624152654.38145-1-ioworker0@gmail.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250624152654.38145-1-ioworker0@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ZmsS1QomoEU0lnf14iKyCE1S2Ky9FlP2qnsVF3vM3yc_1750779265 X-Mimecast-Originator: redhat.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250624_083429_095084_E2E72A67 X-CRM114-Status: GOOD ( 22.92 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 24.06.25 17:26, Lance Yang wrote: > On 2025/6/24 20:55, David Hildenbrand wrote: >> On 14.02.25 10:30, Barry Song wrote: >>> From: Barry Song > [...] >>> diff --git a/mm/rmap.c b/mm/rmap.c >>> index 89e51a7a9509..8786704bd466 100644 >>> --- a/mm/rmap.c >>> +++ b/mm/rmap.c >>> @@ -1781,6 +1781,25 @@ void folio_remove_rmap_pud(struct folio *folio, >>> struct page *page, >>> #endif >>> } >>> +/* We support batch unmapping of PTEs for lazyfree large folios */ >>> +static inline bool can_batch_unmap_folio_ptes(unsigned long addr, >>> + struct folio *folio, pte_t *ptep) >>> +{ >>> + const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; >>> + int max_nr = folio_nr_pages(folio); >> >> Let's assume we have the first page of a folio mapped at the last page >> table entry in our page table. > > Good point. I'm curious if it is something we've seen in practice ;) I challenge you to write a reproducer :P I assume it might be doable through simple mremap(). > >> >> What prevents folio_pte_batch() from reading outside the page table? > > Assuming such a scenario is possible, to prevent any chance of an > out-of-bounds read, how about this change: > > diff --git a/mm/rmap.c b/mm/rmap.c > index fb63d9256f09..9aeae811a38b 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1852,6 +1852,25 @@ static inline bool can_batch_unmap_folio_ptes(unsigned long addr, > const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; > int max_nr = folio_nr_pages(folio); > pte_t pte = ptep_get(ptep); > + unsigned long end_addr; > + > + /* > + * To batch unmap, the entire folio's PTEs must be contiguous > + * and mapped within the same PTE page table, which corresponds to > + * a single PMD entry. Before calling folio_pte_batch(), which does > + * not perform boundary checks itself, we must verify that the > + * address range covered by the folio does not cross a PMD boundary. > + */ > + end_addr = addr + (max_nr * PAGE_SIZE) - 1; > + > + /* > + * A fast way to check for a PMD boundary cross is to align both > + * the start and end addresses to the PMD boundary and see if they > + * are different. If they are, the range spans across at least two > + * different PMD-managed regions. > + */ > + if ((addr & PMD_MASK) != (end_addr & PMD_MASK)) > + return false; You should not be messing with max_nr = folio_nr_pages(folio) here at all. folio_pte_batch() takes care of that. Also, way too many comments ;) You may only batch within a single VMA and within a single page table. So simply align the addr up to the next PMD, and make sure it does not exceed the vma end. ALIGN and friends can help avoiding excessive comments. -- Cheers, David / dhildenb _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv