From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 02D4E238D2E for ; Mon, 17 Feb 2025 19:58:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739822330; cv=none; b=jV/5dSArM38SSZQNQc7tCcFQuHFO0Kg47f/0Uuc7j2OR559JZMCJCyWv4rTlQ8Pe6tpSBL3CYjfnnldF9suz2pCbMEcfHoYxhl05zvevC0IIXn5Nd44f0igH3oma5IjR9ZzJN9dRD+8oNVnrwCvENOs8bxUHdOTanfkizPIjkT0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739822330; c=relaxed/simple; bh=H7EXqVyyi+kLT8T3AFWH4gU/uM442cOf8FS+Ncb8NkM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Rn99PPHkymJT8DWhIIhnW19sJBavQ+YJRpQZNcn4n4LEz+DL8TEa7g/gD5i5WUUwsEmJdsmlKeBW3vMsGdDaIRLgoV/ujz2za4zNMkll69lUlMAwbTkIcP2XCn9qjzS2iboHq+OBCSO5kss3Wa6B9EU3Mz6ZuNOCdKoc2mkTFRU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=XEv90QqL; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XEv90QqL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739822328; 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=NlktFKbt7fWOri2OGRbyYiQR64jGh1ap4Xy3JViDRMo=; b=XEv90QqLiwNBMjF1S27daonlXuEOOLHs7NrLdcZ852Eyi1X0g2ufVb6bYGyDj1wuiNUSyK OOBPeN7XymK/ge0Rmg+nO6mu7L5GXaisEI3ml3V4pcEkt4r95P8NqsEYp/9GUtEx4L6ur7 MgBXpRf8Wjsgw/9gagCKLkl9aewXYac= 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-464-Y5J5T8lfPri70ICso0u0jA-1; Mon, 17 Feb 2025 14:58:46 -0500 X-MC-Unique: Y5J5T8lfPri70ICso0u0jA-1 X-Mimecast-MFC-AGG-ID: Y5J5T8lfPri70ICso0u0jA_1739822326 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-38f44be93a8so748838f8f.1 for ; Mon, 17 Feb 2025 11:58:46 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739822325; x=1740427125; 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=NlktFKbt7fWOri2OGRbyYiQR64jGh1ap4Xy3JViDRMo=; b=egPuQiFU7TwJaAFoGtvXFP+zjQ826MUGyFm6wCYNC6vgTBWE6OIgG9F5BiWF2XhDF6 HBzJImCAIv59dpP01/jA8ER6d8djQTOy8ppq5AQq0w6JaS6P374DJBKuwknIyxfmhIOB BZ3tm92aIMGiSrRSUnPfUVpiPgnc1hM5bR8h2qr52/TbhVogUgOuwrjdkVunE0uCsxzJ +9Pt/4Hm5DzdURKIaCk6lOlGt7OeyusOYPXgsiFs1+t6g/2N4dz8n6Ins5U+ehHFXTeB nQh2zoWwAunUQHpRWo5jESu1lpWsqJ/H9cAAGb3DlRPxE9JdR+ZEcq96Bsqncmz5y95V 8leA== X-Forwarded-Encrypted: i=1; AJvYcCVz0WHM/JK/CGzPFP8uuMgKoIANpEBokVTakUnpJsJIha+fO2Exz3Nbf/IcxGRWVhMLCjxsZdXS36WF5aE=@vger.kernel.org X-Gm-Message-State: AOJu0YzsOR+y6QBbs2r2scRNE0wDdTY4qfwXzx6NOZmg8B9WMdxyBGdm MjbiJRlElD2vcl+uRnXh0Ki+8idphlhzQii+90C9s3TBfsX2b/eHSQ/XOPknswHdd6mWdyEobsv qRhNtrWVA5UFUEjYxeM1AQOP1KSezle5T1iNbrJyV/md7WXTXMUY8RoNdtHGtYw== X-Gm-Gg: ASbGncsCMRovNuJDMDxBiFCACX/xnz5073PLDFwySgW5fqEE1zJiQJYWdLmhnFES0S1 5R8syVkAe/caUO7Kx6QY+3eviwpT6yYacb3qMTmX2k83PhhQ9859U4TsvZb7nnHeTZFlTbv/ZWG P4xBjFPt58TS5+asz0IIDhhY/lianeF34R6j6Q/pRo6nifioHAcgzGIftEXP5eaITzaJuV4lVdH uhtGMHo02SjWq+/SYGx8Dk0X71cXwJv6tHvDUkHm9GF/L/7sH9R7PL0D7PzU9N55naeMZRO2itf wK7q4NsVF21IMgNPqH7UK9OSy06ok7CaBqlzUBn+1s14fxSHzQ1PmQyHuw5ANBg6EEmddi0tdh8 zCEQ0LQ8zlvmre4vFUllpqdpy2WWDig== X-Received: by 2002:a5d:4a43:0:b0:38f:3392:9fd8 with SMTP id ffacd0b85a97d-38f33f2cb57mr8062644f8f.18.1739822325469; Mon, 17 Feb 2025 11:58:45 -0800 (PST) X-Google-Smtp-Source: AGHT+IGmnf+EH+x2w9Z3amJyvk4I4a5QL1krZ5SQiXGUsJvRabwqfhUp4vd7zVPxaXWLqtKKNwXS0Q== X-Received: by 2002:a5d:4a43:0:b0:38f:3392:9fd8 with SMTP id ffacd0b85a97d-38f33f2cb57mr8062617f8f.18.1739822325081; Mon, 17 Feb 2025 11:58:45 -0800 (PST) Received: from ?IPV6:2003:cb:c739:900:900f:3c9e:2f7b:5d0a? (p200300cbc7390900900f3c9e2f7b5d0a.dip0.t-ipconnect.de. [2003:cb:c739:900:900f:3c9e:2f7b:5d0a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f258b4118sm13425148f8f.18.2025.02.17.11.58.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Feb 2025 11:58:43 -0800 (PST) Message-ID: <519c6ef7-ca56-4aac-8e43-f75b17353d66@redhat.com> Date: Mon, 17 Feb 2025 20:58:38 +0100 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 v7 16/20] huge_memory: Add vmf_insert_folio_pmd() To: Alistair Popple Cc: akpm@linux-foundation.org, dan.j.williams@intel.com, linux-mm@kvack.org, Alison Schofield , lina@asahilina.net, zhang.lyra@gmail.com, gerald.schaefer@linux.ibm.com, vishal.l.verma@intel.com, dave.jiang@intel.com, logang@deltatee.com, bhelgaas@google.com, jack@suse.cz, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, dave.hansen@linux.intel.com, ira.weiny@intel.com, willy@infradead.org, djwong@kernel.org, tytso@mit.edu, linmiaohe@huawei.com, peterx@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, david@fromorbit.com, chenhuacai@kernel.org, kernel@xen0n.name, loongarch@lists.linux.dev References: <9f10e88441f3cb26eff6be0c9ef5997844c8c24e.1738709036.git-series.apopple@nvidia.com> <6mmjoe27y63cfe5cycqje63gehgumod3bp7zzgvpz7qehgfuv4@uomvqgizba2m> From: David Hildenbrand Content-Language: en-US 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: <6mmjoe27y63cfe5cycqje63gehgumod3bp7zzgvpz7qehgfuv4@uomvqgizba2m> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17.02.25 05:29, Alistair Popple wrote: > On Mon, Feb 10, 2025 at 07:45:09PM +0100, David Hildenbrand wrote: >> On 04.02.25 23:48, Alistair Popple wrote: >>> Currently DAX folio/page reference counts are managed differently to normal >>> pages. To allow these to be managed the same as normal pages introduce >>> vmf_insert_folio_pmd. This will map the entire PMD-sized folio and take >>> references as it would for a normally mapped page. >>> >>> This is distinct from the current mechanism, vmf_insert_pfn_pmd, which >>> simply inserts a special devmap PMD entry into the page table without >>> holding a reference to the page for the mapping. >>> >>> It is not currently useful to implement a more generic vmf_insert_folio() >>> which selects the correct behaviour based on folio_order(). This is because >>> PTE faults require only a subpage of the folio to be PTE mapped rather than >>> the entire folio. It would be possible to add this context somewhere but >>> callers already need to handle PTE faults and PMD faults separately so a >>> more generic function is not useful. >>> >>> Signed-off-by: Alistair Popple >> >> Nit: patch subject ;) >> >>> >>> --- >>> >>> Changes for v7: >>> >>> - Fix bad pgtable handling for PPC64 (Thanks Dan and Dave) >> >> Is it? ;) insert_pfn_pmd() still doesn't consume a "pgtable_t *" >> >> But maybe I am missing something ... > > At a high-level all I'm trying to do (perhaps badly) is pull the ptl locking one > level up the callstack. > > As far as I can tell the pgtable is consumed here: > > static int insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, > pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write, > pgtable_t pgtable) > > [...] > > if (pgtable) { > pgtable_trans_huge_deposit(mm, pmd, pgtable); > mm_inc_nr_ptes(mm); > pgtable = NULL; > } > > [...] > > return 0; > > Now I can see I failed to clean up the useless pgtable = NULL asignment, which > is confusing because I'm not trying to look at pgtable in the caller (ie. > vmf_insert_pfn_pmd()/vmf_insert_folio_pmd()) to determine if it needs freeing. > So I will remove this assignment. Ahhh, yes, the "pgtable = NULL" confused me, so I was looking for a "pgtable_t *pgtable" being passed instead, that we could manipulate. > > Instead callers just look at the return code from insert_pfn_pmd() - if there > was an error pgtable_trans_huge_deposit(pgtable) wasn't called and if the caller > passed a pgtable it should be freed. Otherwise if insert_pfn_pmd() succeeded > then callers can assume the pgtable was consumed by pgtable_trans_huge_deposit() > and therefore should not be freed. > > Hopefully that all makes sense, but maybe I've missed something obvious too... Yes, you assume that if insert_pfn_pmd() succeeds, the table was consumed, otherwise it must be freed. Thanks! Acked-by: David Hildenbrand -- Cheers, David / dhildenb