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[2003:cb:c706:4e00:31ad:5274:e21c:b59]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4281fb6369esm66618535e9.48.2024.07.30.14.19.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 Jul 2024 14:19:28 -0700 (PDT) Message-ID: <1c527333-e837-4a40-afa8-eb8728332055@redhat.com> Date: Tue, 30 Jul 2024 23:19:27 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/hugetlb: fix hugetlb vs. core-mm PT locking To: James Houghton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Peter Xu , Oscar Salvador , Muchun Song , Baolin Wang References: <20240730200341.1642904-1-david@redhat.com> <3f6c97b5-ccd8-4226-a9ac-78d555b0d048@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-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B191AA0003 X-Stat-Signature: c3fimh9se8feptkn3kcnhng5c1mysdub X-Rspam-User: X-HE-Tag: 1722374379-147902 X-HE-Meta: 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 kL7q6Xgi +ZbH85LIGNo2rcSAU7nJNQuqjQePQb+lftJfQhLStJcEsuGhSbIlR7Vnfp/JP9Ftya3ZPNUIctZZZo2pY+t306N9IcKv6MqyoNHXbM/T85B0tJtCPq7xxoPkzwszAE+0uSWGgxgxTsjBt7oEoODK9qHeb5i1Nml5dtPGIO2+701YF1HHIZH7Dsh3UgfyOeqQuGV0gx5cB0AQzn1WhSwc4xIGxZfuFEQQtTo4uILbPFF7/A9ACPy+29radCDSO/aNHPR2JfZQprqSoEnLB6KMyDTcTbPMeeZpiNT0tdCQJJPweNyoVactnObXAzFXUYctkWE+c6EC0+ec5EkjTpfkB63H5O0awC9NCBAuXKo5NgweAuJ2yEcXGQMOTXGXS+bySQRa4VVcuWtK73n7CJey5cUFljgs9gDa0XW7b4SjQJe0S8MpwH5qrNEc8T4uuETJ4QmT5 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 30.07.24 23:17, James Houghton wrote: > On Tue, Jul 30, 2024 at 2:07 PM David Hildenbrand wrote: >> >> On 30.07.24 23:00, David Hildenbrand wrote: >>> On 30.07.24 22:43, James Houghton wrote: >>>> On Tue, Jul 30, 2024 at 1:03 PM David Hildenbrand wrote: >>>>> diff --git a/include/linux/mm.h b/include/linux/mm.h >>>>> index b100df8cb5857..1b1f40ff00b7d 100644 >>>>> --- a/include/linux/mm.h >>>>> +++ b/include/linux/mm.h >>>>> @@ -2926,6 +2926,12 @@ static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd) >>>>> return ptlock_ptr(page_ptdesc(pmd_page(*pmd))); >>>>> } >>>>> >>>>> +static inline spinlock_t *ptep_lockptr(struct mm_struct *mm, pte_t *pte) >>>>> +{ >>>>> + BUILD_BUG_ON(IS_ENABLED(CONFIG_HIGHPTE)); >>>>> + return ptlock_ptr(virt_to_ptdesc(pte)); >>>> >>>> Hi David, >>>> >>> >>> Hi! >>> >>>> Small question: ptep_lockptr() does not handle the case where the size >>>> of the PTE table is larger than PAGE_SIZE, but pmd_lockptr() does. >>> >>> I thought I convinced myself that leaf page tables are always single >>> pages and had a comment in v1. >>> >>> But now I have to double-check again, and staring at >>> pagetable_pte_ctor() callers I am left confused. >>> >>> It certainly sounds more future proof to just align the pointer down to >>> the start of the PTE table like pmd_lockptr() would. >>> >>>> IIUC, for pte_lockptr() and ptep_lockptr() to return the same result >>>> in this case, ptep_lockptr() should be doing the masking that >>>> pmd_lockptr() is doing. Are you sure that you don't need to be doing >>>> it? (Or maybe I am misunderstanding something.) >>> >>> It's a valid concern even if it would not be required. But I'm afraid I >>> won't dig into the details and simply do the alignment in a v3. >> >> To be precise, the following on top: >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index 1b1f40ff00b7d..f6c7fe8f5746f 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -2926,10 +2926,22 @@ static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd) >> return ptlock_ptr(page_ptdesc(pmd_page(*pmd))); >> } >> >> -static inline spinlock_t *ptep_lockptr(struct mm_struct *mm, pte_t *pte) >> +static inline struct page *ptep_pgtable_page(pte_t *pte) >> { >> + unsigned long mask = ~(PTRS_PER_PTE * sizeof(pte_t) - 1); >> + >> BUILD_BUG_ON(IS_ENABLED(CONFIG_HIGHPTE)); >> - return ptlock_ptr(virt_to_ptdesc(pte)); >> + return virt_to_page((void *)((unsigned long)pte & mask)); >> +} >> + >> +static inline struct ptdesc *ptep_ptdesc(pte_t *pte) >> +{ >> + return page_ptdesc(ptep_pgtable_page(pte)); >> +} >> + >> +static inline spinlock_t *ptep_lockptr(struct mm_struct *mm, pte_t *pte) >> +{ >> + return ptlock_ptr(ptep_ptdesc(pte)); >> } > > Thanks! That looks right to me. Feel free to add > > Reviewed-by: James Houghton Thanks for the review, will send a v3 tomorrow after having wasted more valuable life time setting up the ARM environment again ... :) -- Cheers, David / dhildenb