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[2003:cb:c706:2000:e44c:bc46:d8d3:be5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f258b4423sm20653252f8f.11.2025.02.20.03.05.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Feb 2025 03:05:25 -0800 (PST) Message-ID: Date: Thu, 20 Feb 2025 12:05:23 +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 2/4] mm: page_table_check: use new iteration API To: Luiz Capitulino , linux-kernel@vger.kernel.org, linux-mm@kvack.org, yuzhao@google.com, pasha.tatashin@soleen.com Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, muchun.song@linux.dev References: <85f11743d259d5e4a1f47456fbcda82ff6db9ab3.1739931468.git.luizcap@redhat.com> 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: <85f11743d259d5e4a1f47456fbcda82ff6db9ab3.1739931468.git.luizcap@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 19.02.25 03:17, Luiz Capitulino wrote: > The page_ext_next() function assumes that page extension objects for a > page order allocation always reside in the same memory section, which > may not be true and could lead to crashes. Use the new page_ext > iteration API instead. > > Fixes: cf54f310d0d3 ("mm/hugetlb: use __GFP_COMP for gigantic folios") > Signed-off-by: Luiz Capitulino > --- > mm/page_table_check.c | 39 ++++++++++++--------------------------- > 1 file changed, 12 insertions(+), 27 deletions(-) > > diff --git a/mm/page_table_check.c b/mm/page_table_check.c > index 509c6ef8de400..b52e04d31c809 100644 > --- a/mm/page_table_check.c > +++ b/mm/page_table_check.c > @@ -62,24 +62,20 @@ static struct page_table_check *get_page_table_check(struct page_ext *page_ext) > */ > static void page_table_check_clear(unsigned long pfn, unsigned long pgcnt) > { > + struct page_ext_iter iter; > struct page_ext *page_ext; > struct page *page; > - unsigned long i; > bool anon; > > if (!pfn_valid(pfn)) > return; > > page = pfn_to_page(pfn); > - page_ext = page_ext_get(page); > - > - if (!page_ext) > - return; > - > BUG_ON(PageSlab(page)); > anon = PageAnon(page); > > - for (i = 0; i < pgcnt; i++) { > + rcu_read_lock(); > + for_each_page_ext(page, pgcnt, page_ext, iter) { > struct page_table_check *ptc = get_page_table_check(page_ext); > > if (anon) { > @@ -89,9 +85,8 @@ static void page_table_check_clear(unsigned long pfn, unsigned long pgcnt) > BUG_ON(atomic_read(&ptc->anon_map_count)); > BUG_ON(atomic_dec_return(&ptc->file_map_count) < 0); > } > - page_ext = page_ext_next(page_ext); > } > - page_ext_put(page_ext); > + rcu_read_unlock(); > } [...] > > /* > @@ -140,24 +130,19 @@ static void page_table_check_set(unsigned long pfn, unsigned long pgcnt, > */ > void __page_table_check_zero(struct page *page, unsigned int order) > { > + struct page_ext_iter iter; > struct page_ext *page_ext; > - unsigned long i; > > BUG_ON(PageSlab(page)); > > - page_ext = page_ext_get(page); > - > - if (!page_ext) > - return; > - > - for (i = 0; i < (1ul << order); i++) { > + rcu_read_lock(); > + for_each_page_ext_order(page, order, page_ext, iter) { I would avoid introducing for_each_page_ext_order() and just pass "1 << order" as the page count. > struct page_table_check *ptc = get_page_table_check(page_ext); > > BUG_ON(atomic_read(&ptc->anon_map_count)); > BUG_ON(atomic_read(&ptc->file_map_count)); > - page_ext = page_ext_next(page_ext); > } > - page_ext_put(page_ext); > + rcu_read_unlock(); > } > > void __page_table_check_pte_clear(struct mm_struct *mm, pte_t pte) Apart from that, this looks very nice to me Acked-by: David Hildenbrand -- Cheers, David / dhildenb