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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09FAEC35FFC for ; Sat, 22 Mar 2025 06:17:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 42BF9280002; Sat, 22 Mar 2025 02:17:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3DC50280001; Sat, 22 Mar 2025 02:17:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 255F9280002; Sat, 22 Mar 2025 02:17:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 092A9280001 for ; Sat, 22 Mar 2025 02:17:14 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id EF7DF584D1 for ; Sat, 22 Mar 2025 06:17:13 +0000 (UTC) X-FDA: 83248179546.16.3078323 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf19.hostedemail.com (Postfix) with ESMTP id 5DCE31A0003 for ; Sat, 22 Mar 2025 06:17:11 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iveT+n6p; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf19.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1742624231; a=rsa-sha256; cv=none; b=KR6ClEFu/x1OLPDM/qcNtF1AiNcF7f3uDRpXXYfb3mqYhVSu3foIFXUp8/hLsv/qWWON26 8EaPgPFhRMGZ4jFI9BFMOfKg09RoJTDjl7C391YWlrJ3SEsOTmT+t8UUjDzEk6SDxxysAW 53TBM2I40VfglrbgO9k4MKeVXJrT+Sg= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iveT+n6p; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf19.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1742624231; h=from:from:sender: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:dkim-signature; bh=EENynz7r6mbQr52/+ZHlvqJrL1ejh24/+KFLCLfAOUQ=; b=1Pms9jiEhlgIHniTin41wO4u6YBPBflE8/RSN66BkxbKAPj4g9Vi7S1wznMrhzpUZ5mLf4 aaPOeghG1HHgfjWEvX99UNkqLJbTsMOSjMTPrVWQ1ILIpHtksAKgjQvqjOrYFEDbFjVn1r nHPH5TAXsr6rI+NJCGA68j2H4Ff7kdc= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1742624230; 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=EENynz7r6mbQr52/+ZHlvqJrL1ejh24/+KFLCLfAOUQ=; b=iveT+n6pHG2Dih/I1zYtEn9JPoX7kPQIT8pVM6w+ckl/pkSfjZsduFMlIK36wJrA6PUE8h LlMyTm5lq/9yhL/QmIBk5t2r+9lhr0L+wJPWuLHFYonUUtotWcFXo5BSHQkXaUu7IeqFD5 xbbMsMOg13gPX/DByHZxE19npfw4rmI= 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-52-BS6547mSOGWa7pIblxKpFw-1; Sat, 22 Mar 2025 02:17:09 -0400 X-MC-Unique: BS6547mSOGWa7pIblxKpFw-1 X-Mimecast-MFC-AGG-ID: BS6547mSOGWa7pIblxKpFw_1742624228 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-3912a0439afso1039594f8f.3 for ; Fri, 21 Mar 2025 23:17:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1742624228; x=1743229028; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:references:cc:to:from:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=EENynz7r6mbQr52/+ZHlvqJrL1ejh24/+KFLCLfAOUQ=; b=ehqLPsZVRwbzW6CFGAaJfyGmVFVxDHzQ0zM+Ux6POz1bCavBbQpULl2ACCHIsHhsOp dbV1+owyhKIERdnLx9nDbfbGddyZvq5P/XRRzDOqfIOltgRIVRPDooS+noYLIEKGgf3R UztG/GhwoTMne7fjKkCoLDxTkueHHWoNBv9gSAX/Ws3MJD59NjHWLY+wxOqXOtuiJ5T/ L3KEEEK7+wETfjOXFmSAn6iv3XG+h40jx3KAtbYqVR/UhpdZ/mlAQL40TMCwfhUrNhTb MPxVGBfrB7oM5J+6cOkEnSIgLL+fVmwYpsFWPfq/ux5vaDqxspkPLUY53nwYqd0te8Qd U8+w== X-Forwarded-Encrypted: i=1; AJvYcCW0JyrAZNpGTcSpy06XdE/2SFn+9bLzlfsZmhatk/zYSF3v8WkaTyO1vIt8BTko19F8nvvjUr9rZQ==@kvack.org X-Gm-Message-State: AOJu0Yx8MAGNgRVPkcp6+wUPk7wiI6WY3GM/gGcm1XZdTaPR3068IplX wAZtvNon6K8TCVS1hSYBkBOOI/ah3tP83fWCJF5FjmAh2zKvb2mwX1zAG7fqIGU+hhgWtHLEJzs CVAXZnMQKZAcsrQLFTeKO/h6890g2fgfEsuk0N+kXuz2E3vAUHWnzLmaVX+BILA== X-Gm-Gg: ASbGncsg2HoHZYR1IkBNM1qVDAHAGiBqICM17s3Lcjv/GRH3MiVc6HUKHj+pEaNUGZ9 WOCQU94WRBfiBbtBrc1EpLmT2mMH4r6k6QNZQmjIlilbQWH3qClxfpmd9DBBidWlNEGRCSw0l5t nfEMFiBZajOKc8yRsTO4pPGPEs5SEmMP/7dXn3sOWjDkRbQOKewOLo4b3cKJ12AJgoAovGa28kM r7RpI+ALCkJyLKq7Ul6jWnPwOeixPdC5wSOCM1uHS+yR3o8W0RkwL4MTIntAxACqSJS/+RfXQZD VmzPe7rR7agQk94= X-Received: by 2002:a05:6000:1547:b0:38d:d603:ff46 with SMTP id ffacd0b85a97d-3997f8f9ea4mr6082177f8f.14.1742624227667; Fri, 21 Mar 2025 23:17:07 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEEsoD08wuw08TfcaVbInJJiPy4pEpDQgFFRgcHWvDRsbA/+LeAQabK7tvxTdI3qjxagn3G9Q== X-Received: by 2002:a05:6000:1547:b0:38d:d603:ff46 with SMTP id ffacd0b85a97d-3997f8f9ea4mr6082159f8f.14.1742624227172; Fri, 21 Mar 2025 23:17:07 -0700 (PDT) Received: from [10.239.241.125] ([88.128.92.39]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3997f9a3f76sm4348252f8f.37.2025.03.21.23.17.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Mar 2025 23:17:06 -0700 (PDT) Message-ID: <21f89b73-aaae-4674-aea2-aefc7a4847d9@redhat.com> Date: Sat, 22 Mar 2025 07:17:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/7] mm/mremap: introduce more mergeable mremap via MREMAP_RELOCATE_ANON From: David Hildenbrand To: Jann Horn , Lorenzo Stoakes Cc: Andrew Morton , Vlastimil Babka , "Liam R . Howlett" , Suren Baghdasaryan , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <182bf1ce-1b67-4243-854b-4d0c26aae563@redhat.com> 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: <182bf1ce-1b67-4243-854b-4d0c26aae563@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 663gmYcJzeBvkkVN6TlUPucLxk9qFxjVsvoNCmFwV5U_1742624228 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 5DCE31A0003 X-Stat-Signature: kw9cp4mtgrk8jspyaxfmz4ung3kc6dd3 X-HE-Tag: 1742624231-496726 X-HE-Meta: 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 6YBLJOzd 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 22.03.25 06:33, David Hildenbrand wrote: > On 22.03.25 01:14, Jann Horn wrote: >> On Fri, Mar 21, 2025 at 10:54 PM Lorenzo Stoakes >> wrote: >>> diff --git a/mm/mremap.c b/mm/mremap.c >>> index 0865387531ed..bb67562a0114 100644 >>> --- a/mm/mremap.c >>> +++ b/mm/mremap.c >> [...] >>> +/* >>> + * If the folio mapped at the specified pte entry can have its index and mapping >>> + * relocated, then do so. >>> + * >>> + * Returns the number of pages we have traversed, or 0 if the operation failed. >>> + */ >>> +static unsigned long relocate_anon(struct pagetable_move_control *pmc, >>> + unsigned long old_addr, unsigned long new_addr, pte_t pte, >>> + bool undo) >>> +{ >>> + struct page *page; >>> + struct folio *folio; >>> + struct vm_area_struct *old, *new; >>> + pgoff_t new_index; >>> + unsigned long ret = 1; >>> + >>> + old = pmc->old; >>> + new = pmc->new; >>> + >>> + /* Ensure we have truly got an anon folio. */ >>> + page = vm_normal_page(old, old_addr, pte); >>> + if (!page) >>> + return ret; >>> + folio = page_folio(page); >>> + folio_lock(folio); >>> + >>> + /* no-op. */ >>> + if (!folio_test_anon(folio) || folio_test_ksm(folio)) >>> + goto out; >>> + >>> + /* >>> + * This should not happen as we explicitly disallow this, but check >>> + * anyway. >>> + */ >>> + if (folio_test_large(folio)) { >>> + ret = 0; >>> + goto out; >>> + } >> >> Do I understand correctly that you assume here that the page is >> exclusively mapped? Maybe we could at least >> WARN_ON(folio_mapcount(folio) != 1) or something like that? >> >> (I was also wondering if the PageAnonExclusive bit is somehow >> relevant, but we should probably not look at or touch that here, >> unless we want to think about cases where we _used to_ have a child >> from which the page may have been GUP'd...) > > UFFDIO_MOVE implements something similar. Right now we keep it simple: > > if (folio_test_large(src_folio) || > folio_maybe_dma_pinned(src_folio) || > !PageAnonExclusive(&src_folio->page)) { > err = -EBUSY; > goto out; > } > > Whereby we > > a) Make sure we cover all PTEs (-> small folio, single PTE). Large > PTE-mapped folios are split. > > b) Make sure there are no GUP pins (maybe not required here?) > > c) The folio is exclusive to this process On additional note as my memory comes back: if PAE is set, there cannot be other (inactive) mappings from the swapcache. So whenever we use folio lock + mapcount data, the possibility of the swapcache (having inactive mappings from other processes etc.) must be considered. -- Cheers, David / dhildenb