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[2003:cb:c717:5f00:c949:6700:cce1:e60b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-354fa39314dsm2112045f8f.112.2024.05.23.13.38.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 May 2024 13:38:42 -0700 (PDT) Message-ID: <0d80abd4-fbce-4ac1-b088-ec15dee65a55@redhat.com> Date: Thu, 23 May 2024 22:38:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 3/6] mm/zsmalloc: use a proper page type From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , "Matthew Wilcox (Oracle)" , Mike Rapoport , Minchan Kim , Sergey Senozhatsky , Hyeonggon Yoo <42.hyeyoo@gmail.com> References: <20240522210341.1030552-1-david@redhat.com> <20240522210341.1030552-4-david@redhat.com> <2563ea6b-7c65-46a0-adf3-552f2e863c94@redhat.com> 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: <2563ea6b-7c65-46a0-adf3-552f2e863c94@redhat.com> 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-Rspamd-Queue-Id: AF4FF4000C X-Stat-Signature: 31i7ozhjok7sm1wcxk1ten8xawq34e5f X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1716496730-849911 X-HE-Meta: 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 v1HyeBRy 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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 23.05.24 16:55, David Hildenbrand wrote: > On 22.05.24 23:03, David Hildenbrand wrote: >> Let's clean it up: use a proper page type and store our data (offset >> into a page) in the lower 16 bit as documented. >> >> We'll have to restrict ourselves to <= 64KB base page size (so the offset >> fits into 16 bit), which sounds reasonable. Unfortunately, we don't have >> any space to store it elsewhere for now. >> >> Based on this, we should do a proper "struct zsdesc" conversion, as >> proposed in [1]. >> >> This removes the last _mapcount/page_type offender. >> >> [1] https://lore.kernel.org/all/20231130101242.2590384-1-42.hyeyoo@gmail.com/ >> >> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> >> Signed-off-by: David Hildenbrand >> --- >> include/linux/page-flags.h | 3 +++ >> mm/Kconfig | 1 + >> mm/zsmalloc.c | 23 +++++++++++++++++++---- >> 3 files changed, 23 insertions(+), 4 deletions(-) >> >> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h >> index ed9ac4b5233d..ccaf16656de9 100644 >> --- a/include/linux/page-flags.h >> +++ b/include/linux/page-flags.h >> @@ -959,6 +959,7 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) >> #define PG_guard 0x00080000 >> #define PG_hugetlb 0x00100800 >> #define PG_slab 0x00200000 >> +#define PG_zsmalloc 0x00400000 >> >> #define PageType(page, flag) \ >> ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) >> @@ -1073,6 +1074,8 @@ FOLIO_TYPE_OPS(hugetlb, hugetlb) >> FOLIO_TEST_FLAG_FALSE(hugetlb) >> #endif >> >> +PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc) >> + >> /** >> * PageHuge - Determine if the page belongs to hugetlbfs >> * @page: The page to test. >> diff --git a/mm/Kconfig b/mm/Kconfig >> index b4cb45255a54..0371d79b1b75 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -190,6 +190,7 @@ config ZSMALLOC >> tristate >> prompt "N:1 compression allocator (zsmalloc)" if ZSWAP >> depends on MMU >> + depends on PAGE_SIZE_LESS_THAN_256KB # we want <= 64KB >> help >> zsmalloc is a slab-based memory allocator designed to store >> pages of various compression levels efficiently. It achieves >> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c >> index b42d3545ca85..6f0032e06242 100644 >> --- a/mm/zsmalloc.c >> +++ b/mm/zsmalloc.c >> @@ -20,7 +20,8 @@ >> * page->index: links together all component pages of a zspage >> * For the huge page, this is always 0, so we use this field >> * to store handle. >> - * page->page_type: first object offset in a subpage of zspage >> + * page->page_type: PG_zsmalloc, lower 16 bit locate the first object >> + * offset in a subpage of a zspage >> * >> * Usage of struct page flags: >> * PG_private: identifies the first component page >> @@ -450,14 +451,22 @@ static inline struct page *get_first_page(struct zspage *zspage) >> return first_page; >> } >> >> +static inline void reset_first_obj_offset(struct page *page) >> +{ >> + page->page_type |= 0xffff; >> +} >> + >> static inline unsigned int get_first_obj_offset(struct page *page) >> { >> - return page->page_type; >> + return page->page_type & 0xffff; >> } >> >> static inline void set_first_obj_offset(struct page *page, unsigned int offset) >> { >> - page->page_type = offset; >> + BUILD_BUG_ON(PAGE_SIZE & ~0xffff); > > Buildbot is correctly complaining with PAGE_SIZE=64KiB. > > We must check BUILD_BUG_ON((PAGE_SIZE -1) & ~0xffff); ... and I'll have to resolve the "select ZSMALLOC" situation. :) -- Cheers, David / dhildenb