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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5236d2e9ad9sm2710005e87.178.2024.05.21.02.56.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 May 2024 02:56:55 -0700 (PDT) Message-ID: <338b4d56-7e5a-4d8f-8908-610f2c59e29e@redhat.com> Date: Tue, 21 May 2024 11:56:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/hugetlb: Move vmf_anon_prepare upfront in hugetlb_wp To: Oscar Salvador , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Muchun Song , Vishal Moola References: <20240521073446.23185-1-osalvador@suse.de> 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: <20240521073446.23185-1-osalvador@suse.de> X-Mimecast-Spam-Score: 0 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-Server: rspam09 X-Rspamd-Queue-Id: EE78710000E X-Stat-Signature: mrsgtg4rfb4pkwi5hy4bw55hcxntg6ji X-HE-Tag: 1716285422-790397 X-HE-Meta: U2FsdGVkX19I7rFSL2weAZjICgnzFP/ZlgVnpTxcy9KuZNmK2pe1IUNi42wMZBmH2oDs4/NA3C6HIiNmV3ojt85OA29d8PBXTWg9aanMqVfnDq8KxqH63R9o7Z4Jio+nsZeQqGL4hdAhwt6G/gG7B8AxlAGN1ScElWWGO4onqsTKIOZT0IsBcaWStMq66YgkU5PTCA1kb1HxbMrLKBZX8fR08yg0gcyG8eG0Nwy5UZgtv0vr3OIjUBRAISu+1X/AvUdTFyKPxpbNPULHTy52rKjvsVbuveS2oxiV9bYhxxlmgSOHP/PTdN43fniBOYZafVOQmwyg/CCCJANLgorbSZvftyHn06tjeVyIN7DwZJ0dtzkNhJIWZDMyU2TCNZRS32hoKRRLOyIiuNI+r/mceRmwAhi4tPDt2TEi5odOEfwrQ7HzfUxkPMhCAqoJfP5hkFs4xsPa8chlPnTYUuKDpnKLyhTMH+67EBBGjh3OYEmb3Dy4DaYPKkxjUcJ/jagEAHwdn48cp/7avlXQO8NCkPq6Dyo95d2GgjStKoJDzpO0KOVvD6iJBxftpZhHAbX3StDG3RL6iiUx2y1WAw1I5kBxxp2WZ4MP4w+qLqzm9RQXhc3qMxyvTPwWHBVMjZGANp8GlZwaz5/MhlX9uulHGfwzYNBDKv6G0wJ/GT41M3tbZ4MDxVt8XTEwbkhIWFRqlj9Fd/tUwMBsUV/BEaZtAMMUsRfPE0f8VGozdbHCnbEetIz5UWYB1O6qsav3OxTSbYeoU/QBMp67InBEqq1yJCU/v9xAxpta4b6KrVBh3G+z5EG1oqKPzRdxyyPWF4/L31N/kNXmb1JvdkeF9pccmPAvhWmhypitg7lUunmyEz3Ri2b2nD7sB0VUV7b+wUUBgSko1uFJ7P5vrE4u4GlrUy5SQF3L8xo77hOiA/qev+Q1t3a+lNchIXdVSCVLWb/RXJjvavx8eTze3i+ylY2 5cqmMYUY 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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 21.05.24 09:34, Oscar Salvador wrote: > hugetlb_wp calls vmf_anon_prepare() after having allocated a page, which > means that we might need to call restore_reserve_on_error() upon error. > vmf_anon_prepare() releases the vma lock before returning, but > restore_reserve_on_error() expects the vma lock to be held by the caller. > > Fix it by calling vmf_anon_prepare() before allocating the page. > > Signed-off-by: Oscar Salvador > Fixes: 9acad7ba3e25 ("hugetlb: use vmf_anon_prepare() instead of anon_vma_prepare()") > --- > I did not hit this bug, I just spotted this because I was looking at hugetlb_wp > for some other reason. And I did not want to get creative to see if I could > trigger this so I could get a backtrace. > My assumption is that we could trigger this if 1) this was a shared mapping, > so no anon_vma and 2) we call in GUP code with FOLL_WRITE, which would cause > the FLAG_UNSHARE to be passed, so we will end up in hugetlb_wp(). FOLL_WRITE should never result in FLAG_UNSHARE. > > mm/hugetlb.c | 17 +++++++++-------- > 1 file changed, 9 insertions(+), 8 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 6be78e7d4f6e..eb0d8a45505e 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6005,6 +6005,15 @@ static vm_fault_t hugetlb_wp(struct folio *pagecache_folio, > * be acquired again before returning to the caller, as expected. > */ > spin_unlock(vmf->ptl); > + > + /* > + * When the original hugepage is shared one, it does not have > + * anon_vma prepared. > + */ > + ret = vmf_anon_prepare(vmf); > + if (unlikely(ret)) > + goto out_release_old; > + > new_folio = alloc_hugetlb_folio(vma, vmf->address, outside_reserve); > > if (IS_ERR(new_folio)) { > @@ -6058,14 +6067,6 @@ static vm_fault_t hugetlb_wp(struct folio *pagecache_folio, > goto out_release_old; > } > > - /* > - * When the original hugepage is shared one, it does not have > - * anon_vma prepared. > - */ > - ret = vmf_anon_prepare(vmf); > - if (unlikely(ret)) > - goto out_release_all; > - > if (copy_user_large_folio(new_folio, old_folio, vmf->real_address, vma)) { > ret = VM_FAULT_HWPOISON_LARGE | VM_FAULT_SET_HINDEX(hstate_index(h)); > goto out_release_all; The joy of hugetlb reservation code. LGTM -- Cheers, David / dhildenb