From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 EB0281BDA86 for ; Tue, 6 Aug 2024 10:24:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722939891; cv=none; b=Yna07DvpPtDKVxFQP0ChAp0nc79qsH3KMLwUyFe5zR6OHWnLNIwzCIPQWmn9l+1OHO7MbXpQXZ2hJMCmPO5onO7Dv9m2d9NPTMA+AbZfJOkxcn5iyl2dQTI3oPxO3WedNAlu8a1lYHv7tM6W/+N3ZAGL4zTipXdMn9wZ4I5PKXw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722939891; c=relaxed/simple; bh=HuWX+vrC1Cp3pDD3J+tpe61DVfReUbkB6foFuxdjH+A=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=NnzMn35AF6nZ1cM7DR+4XaM6qNpczezT359Hz7dpYvueBbkZQkbGNvuNgd/T3Ck2POiGP5MMzoKiRTjxhwcTgarGo9/6OAQllwxajPIOb+pbap2dDJUyQjXFnFutxgqgJJi/sycKVejQC/O1Hm1Rg4jqRY4oQvLckE418hWPGlE= 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=I2mSskgM; arc=none smtp.client-ip=170.10.129.124 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="I2mSskgM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722939889; 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=DoZ2AeUPUcckuQeDBJI84lvVHjk0eASPXLtUIbrijoY=; b=I2mSskgMVHEkrYSwqNM4rG8ZyZDP0sLAH/MWodI5k+Hx8YlCM2Z6dSR7D4g5AdRH4CqbOL jhepWBOPUSiLvcuVi1F5BEqUw84LWEpfGAKQeea7EkSNxx1e4clfU/9HXi6yJyZO8SQs96 gFc95rxSwIwW2slQliOizD6Dqbi+efs= Received: from mail-lj1-f197.google.com (mail-lj1-f197.google.com [209.85.208.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-183-1DJwABG1OWC_upYP5t24pQ-1; Tue, 06 Aug 2024 06:24:47 -0400 X-MC-Unique: 1DJwABG1OWC_upYP5t24pQ-1 Received: by mail-lj1-f197.google.com with SMTP id 38308e7fff4ca-2ef1b9a466cso6206411fa.3 for ; Tue, 06 Aug 2024 03:24:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722939886; x=1723544686; 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=DoZ2AeUPUcckuQeDBJI84lvVHjk0eASPXLtUIbrijoY=; b=cnLVbX9EAjT+xTyhTTOqfILeLxGa6gfToAd3GhQ6t0xE3I6bQL1biI5E44i1L/Gqhf NtxjiCseTVxGy6PtiG1pw/CH7J6sUmxpfKKIpprMjLtHF8HOfpP9IpMh3WJR+OuMv4Jf cO9pliK8ou92TWH1iMvFm+DU7FUWoGdCZMTFYYtEkBGLjK9BSBnQKMKJ/MflVoFWxBVn deFH6dsxfKx1722MwZvF+5ou3CsMS+c6DykTojPAmqDW5+u9+sSJmTUt4R+a9+nfp+2t ZMQEW8tQ53RHcD4VpsdqcfIa58B04r0fSAPX+dscy97FcHI7aFRl496o9cbipQcJtB0z guog== X-Forwarded-Encrypted: i=1; AJvYcCXDVAExodC9fOxhMD9Yz5N/hrdagJp41SAObiYwPg7pUEY2ch2yQ9bMgQsnnc61pmic5+82SE6uEjhon2tFIAMcf1ixjWgcYgwlKyyk6g== X-Gm-Message-State: AOJu0YzHi4uLSpSNFiC2IKNt31wCrATb+8Vw8cZD2sXIkpXLj8frqD0L cBz4lmVhbhh9XQkaJ6t93zLBg0SvAjSB8WWRZp4WrZ5rwGpZubrhHPt8rF1mx2gFiJPmh6vLxoo bPCNL5umvLiC5Sy2LEQ7iX4bLFVTPClBSqJQStPukLbgtp9TbHr1wU46Umyf2nAU= X-Received: by 2002:a2e:6a19:0:b0:2ef:18b7:440a with SMTP id 38308e7fff4ca-2f15aabcb81mr95034431fa.22.1722939886121; Tue, 06 Aug 2024 03:24:46 -0700 (PDT) X-Google-Smtp-Source: AGHT+IG8itjc3h8PngLh6sckeQFWJdV4aDIkdExLfu67u6p2gXb+5+zksdac7hw0FLiIq9dg6z+/MQ== X-Received: by 2002:a2e:6a19:0:b0:2ef:18b7:440a with SMTP id 38308e7fff4ca-2f15aabcb81mr95034221fa.22.1722939885539; Tue, 06 Aug 2024 03:24:45 -0700 (PDT) Received: from ?IPV6:2003:cb:c73f:8500:f83c:3602:5300:88af? (p200300cbc73f8500f83c3602530088af.dip0.t-ipconnect.de. [2003:cb:c73f:8500:f83c:3602:5300:88af]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-428e6e7cc3asm174941185e9.34.2024.08.06.03.24.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 Aug 2024 03:24:45 -0700 (PDT) Message-ID: Date: Tue, 6 Aug 2024 12:24:43 +0200 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 07/11] mm/huge_memory: convert split_huge_pages_pid() from follow_page() to folio_walk From: David Hildenbrand To: Ryan Roberts , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , "Matthew Wilcox (Oracle)" , Jonathan Corbet , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Gerald Schaefer , Mark Brown References: <20240802155524.517137-1-david@redhat.com> <20240802155524.517137-8-david@redhat.com> 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 06.08.24 12:03, David Hildenbrand wrote: > On 06.08.24 11:56, David Hildenbrand wrote: >> On 06.08.24 11:46, Ryan Roberts wrote: >>> On 02/08/2024 16:55, David Hildenbrand wrote: >>>> Let's remove yet another follow_page() user. Note that we have to do the >>>> split without holding the PTL, after folio_walk_end(). We don't care >>>> about losing the secretmem check in follow_page(). >>> >>> Hi David, >>> >>> Our (arm64) CI is showing a regression in split_huge_page_test from mm selftests from next-20240805 onwards. Navigating around a couple of other lurking bugs, I was able to bisect to this change (which smells about right). >>> >>> Newly failing test: >>> >>> # # ------------------------------ >>> # # running ./split_huge_page_test >>> # # ------------------------------ >>> # # TAP version 13 >>> # # 1..12 >>> # # Bail out! Still AnonHugePages not split >>> # # # Planned tests != run tests (12 != 0) >>> # # # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 >>> # # [FAIL] >>> # not ok 52 split_huge_page_test # exit=1 >>> >>> It's trying to split some pmd-mapped THPs then checking and finding that they are not split. The split is requested via /sys/kernel/debug/split_huge_pages, which I believe ends up in this function you are modifying here. Although I'll admit that looking at the change, there is nothing obviously wrong! Any ideas? >> >> Nothing jumps at me as well. Let me fire up the debugger :) > > Ah, very likely the can_split_folio() check expects a raised refcount > already. Indeed, the following does the trick! Thanks Ryan, I could have sworn I ran that selftest as well. TAP version 13 1..12 ok 1 Split huge pages successful ok 2 Split PTE-mapped huge pages successful # Please enable pr_debug in split_huge_pages_in_file() for more info. # Please check dmesg for more information ok 3 File-backed THP split test done ... @Andrew, can you squash the following? From e5ea585de3e089ea89bf43d8447ff9fc9b371286 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Tue, 6 Aug 2024 12:08:17 +0200 Subject: [PATCH] fixup: mm/huge_memory: convert split_huge_pages_pid() from follow_page() to folio_walk We have to teach can_split_folio() that we are not holding an additional reference. Signed-off-by: David Hildenbrand --- include/linux/huge_mm.h | 4 ++-- mm/huge_memory.c | 8 ++++---- mm/vmscan.c | 2 +- 3 files changed, 7 insertions(+), 7 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index e25d9ebfdf89..ce44caa40eed 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -314,7 +314,7 @@ unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long add unsigned long len, unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags); -bool can_split_folio(struct folio *folio, int *pextra_pins); +bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins); int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, unsigned int new_order); static inline int split_huge_page(struct page *page) @@ -470,7 +470,7 @@ thp_get_unmapped_area_vmflags(struct file *filp, unsigned long addr, } static inline bool -can_split_folio(struct folio *folio, int *pextra_pins) +can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins) { return false; } diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 697fcf89f975..c40b0dcc205b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3021,7 +3021,7 @@ static void __split_huge_page(struct page *page, struct list_head *list, } /* Racy check whether the huge page can be split */ -bool can_split_folio(struct folio *folio, int *pextra_pins) +bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins) { int extra_pins; @@ -3033,7 +3033,7 @@ bool can_split_folio(struct folio *folio, int *pextra_pins) extra_pins = folio_nr_pages(folio); if (pextra_pins) *pextra_pins = extra_pins; - return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins - 1; + return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins - caller_pins; } /* @@ -3201,7 +3201,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, * Racy check if we can split the page, before unmap_folio() will * split PMDs */ - if (!can_split_folio(folio, &extra_pins)) { + if (!can_split_folio(folio, 1, &extra_pins)) { ret = -EAGAIN; goto out_unlock; } @@ -3537,7 +3537,7 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start, * can be split or not. So skip the check here. */ if (!folio_test_private(folio) && - !can_split_folio(folio, NULL)) + !can_split_folio(folio, 0, NULL)) goto next; if (!folio_trylock(folio)) diff --git a/mm/vmscan.c b/mm/vmscan.c index 31d13462571e..a332cb80e928 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1227,7 +1227,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, goto keep_locked; if (folio_test_large(folio)) { /* cannot split folio, skip it */ - if (!can_split_folio(folio, NULL)) + if (!can_split_folio(folio, 1, NULL)) goto activate_locked; /* * Split partially mapped folios right away. -- 2.45.2 -- Cheers, David / dhildenb