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 BCFC6C021AA for ; Tue, 18 Feb 2025 16:12:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5084A28014E; Tue, 18 Feb 2025 11:12:37 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B7D828013C; Tue, 18 Feb 2025 11:12:37 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 30B6128014E; Tue, 18 Feb 2025 11:12:37 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 12A8F28013C for ; Tue, 18 Feb 2025 11:12:37 -0500 (EST) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id C2AED45434 for ; Tue, 18 Feb 2025 16:12:36 +0000 (UTC) X-FDA: 83133558312.27.06ADC8B Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf07.hostedemail.com (Postfix) with ESMTP id 4947B40016 for ; Tue, 18 Feb 2025 16:12:34 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="hr/ywwtv"; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf07.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1739895154; a=rsa-sha256; cv=none; b=E8YC8Huv3DscCRMuMX7YCEOOHJv0rSg9i7aqI+8YIdN3iRO0ynhqIKmVZ5DsWxLkQru5P5 kP+t8Fo2Lj7RAQMnk569CvyHNBlSmt3u7JUZUaWDvUsM1gnh5JdGupYDavHfoFxcMX9/im ZsLw4rgh2vjehhJyHnIpXOGJ61xNDZs= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="hr/ywwtv"; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf07.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 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=1739895154; 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=qPrl3VBWVHIaEvfm5FHekwOGQkEzqzqF8ZKou2UTYEw=; b=Oxg9Tudc5mxHM2rWx/EPzZbC2Hkmw/RPgdF6kydLHDtgxTZEyjxfq6UdSsQcXxeFVq2j7G q3jcmMV+9OCQvtRL+x3c/05BsIvLI2gNWY4RpydvGYg4cNMPmApTDi8IXEePnoq7Mto/YN s8z1WkavarRKdcsRnJ4CqYf01/fv4ks= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739895153; 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=qPrl3VBWVHIaEvfm5FHekwOGQkEzqzqF8ZKou2UTYEw=; b=hr/ywwtv5e4EfBC3b1q/45VtXDwFd8n3TaNQQ4E2pQfO/WNx/c4ov4ZbId2VZAimjq/XnG vkNVh+Iqgz+HgN5KKCF3NMwSNtxDA5PpbOhEubfJG0arRVUWOP/5GI3/S5C/zaPcFooRgX PMtl2dzjW4y4GhgJz3nOLXLw9y6GPGE= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-639-l_DGIS2gPOOMPzR4RD14GQ-1; Tue, 18 Feb 2025 11:12:32 -0500 X-MC-Unique: l_DGIS2gPOOMPzR4RD14GQ-1 X-Mimecast-MFC-AGG-ID: l_DGIS2gPOOMPzR4RD14GQ_1739895151 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-43933bdcce0so47351395e9.2 for ; Tue, 18 Feb 2025 08:12:32 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739895151; x=1740499951; 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=qPrl3VBWVHIaEvfm5FHekwOGQkEzqzqF8ZKou2UTYEw=; b=OPQgMwI/xr3BQGW8BUjk8pS4DCW46r18vki/7HhKqk6zylUtOCtIbvuxEZmiU9Bfr0 EJ5LKVDCev5Vt59juGOpUYw0Z1b++D7sZcVxT/RumqWURZxYmYoPMGlKmGh6CT/6RcLP 5L/eCqZ+zYEPO54nDOYrFU1avgSrBDf+tejDdR064rN6vwGGSZszCDfMsUOife8nrM46 AWfZBrcakHQrvSHe+wCFcq6PAaGVCE8a6v55/6N0on6hqCUt2mTcZ2kH3z3AaE0VXk2w ogjXe9o2oETn9QSHOlmSQ6oSdqmA/DverB+DluF0N1gRpBTltu1cOLwmTs+zWYz0TUuR W8VA== X-Gm-Message-State: AOJu0YzgUYPhUkZO4OILdNkXgdby8c+dnC0OqIjmTmXY660zftU+NaN6 rlB0/xO2X+w0PtP26NXopKoDgh5fQBz5lTWbscrynEOO+xjn9gcQoQ5tf0j3EtOLr2kxInH4XGu 4NNZFyuh1RssCu8ph/AulL3QsbyLIfVqxy4sKzct9haBaN7Qt X-Gm-Gg: ASbGncvlAqYpsPJIMsu/MlK7+OrDoN7PyV9PFhg9hAvKv/1C17tjhHv7fq920cz9Lmk AUUBcbBnPOBm5EYGKVKZlsFldD62UHdZUpFqP8pximxzZKsATbFZxAj+VomfGfxgTKfphbEEzMk Rj0jolDAIwSOvCLS+h2RZd5SFCeG27gZ+Ja6oKf5hVHC2o2zT8dbK4K4/+6sxvUbd+rgNj59dBf 38Eo6TyzZE0M7jtiQup5lQniekGANU2uHeSejlSqLgc6+ClTyKCJMmhPPjsXIbGL9neI5itwKaa O5LulmHyfq1DdmYVoV3l0U8BoxYTxd678Q== X-Received: by 2002:a05:600c:3ba6:b0:439:91dd:cfaf with SMTP id 5b1f17b1804b1-43999da55damr2421675e9.18.1739895151245; Tue, 18 Feb 2025 08:12:31 -0800 (PST) X-Google-Smtp-Source: AGHT+IH92K++cC6xDJY2j/PMK6R78q23skDZQsnW1aMpOh6cHc3xvEiDq38ZeyklE0eZ+XCX3RGQFw== X-Received: by 2002:a05:600c:3ba6:b0:439:91dd:cfaf with SMTP id 5b1f17b1804b1-43999da55damr2421325e9.18.1739895150812; Tue, 18 Feb 2025 08:12:30 -0800 (PST) Received: from [192.168.3.141] (p5b0c61a2.dip0.t-ipconnect.de. [91.12.97.162]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f259fdce7sm15527728f8f.96.2025.02.18.08.12.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 08:12:29 -0800 (PST) Message-ID: Date: Tue, 18 Feb 2025 17:12:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 1/8] xarray: add xas_try_split() to split a multi-index entry. To: Zi Yan Cc: linux-mm@kvack.org, Andrew Morton , "Kirill A . Shutemov" , "Matthew Wilcox (Oracle)" , Ryan Roberts , Hugh Dickins , Yang Shi , Miaohe Lin , Kefeng Wang , Yu Zhao , John Hubbard , Baolin Wang , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250211155034.268962-1-ziy@nvidia.com> <20250211155034.268962-2-ziy@nvidia.com> <0bb75517-9418-4145-8aa8-b05373010711@redhat.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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 8SyFRYuEikqkM3uBLjvkFfaXdzpP9by_mOZYBgrAubI_1739895151 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 4947B40016 X-Rspamd-Server: rspam12 X-Stat-Signature: 1i6fdn5u63i4azu6b961yjnei9zfgc7t X-HE-Tag: 1739895154-490121 X-HE-Meta: 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 9DcIE716 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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: >> >> Now, can it happen that xas_try_split() would ever perform a partial split in any way, when invoked from __split_unmapped_folio(), such that we run into the do { } while(); loop and fail with -ENOMEM after already having performed changes -- xas_update(). >> >> Or is that simply impossible? > > Right. It is impossible. xas_try_split() either splits by copying @entry > to all the replacement entries, or is trying to allocate a new xa_node, > which can result in -ENOMEM. These two will not be mixed. > >> >> Maybe it's just the do { } while(); loop in there that is confusing me. (again, no expert) > > Yeah, that the do while loop is confusing. Let me restructure the code > so that the do while loop only runs in the @entry copy case not the > xa_node allocation case. Great! > >> >>> xas_try_split() imposes what kind of split it does and is usually used to >>> split from order N to order N-1: >> >> You mean that old_order -> split_order will in the case of __split_unmapped_folio() always be a difference of 1? > > Yes for !uniform_split case. For uniform_split case (split_huge_page*() uses), > xas_split() is used and all required new xa_node are preallocated by > xas_split_alloc() in __folio_split(). Got it, thanks! -- Cheers, David / dhildenb