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Mon, 27 Oct 2025 15:34:50 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id FTU0CxqR/2ifUgAAD6G6ig (envelope-from ); Mon, 27 Oct 2025 15:34:50 +0000 Message-ID: Date: Mon, 27 Oct 2025 16:34:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 01/17] slab: Reimplement page_slab() Content-Language: en-US To: "Matthew Wilcox (Oracle)" , Andrew Morton , Alexander Potapenko , Marco Elver Cc: Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , linux-mm@kvack.org, Dmitry Vyukov , kasan-dev References: <20251024204434.2461319-1-willy@infradead.org> <20251024204434.2461319-2-willy@infradead.org> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20251024204434.2461319-2-willy@infradead.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 39r69ordgsh6zibt1qn8xmtr5bfogwzq X-Rspamd-Queue-Id: E2C5B1C000C X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1761579291-948237 X-HE-Meta: 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 1QuJg8fs gaeWto7l62hnVD8c= 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 10/24/25 22:44, Matthew Wilcox (Oracle) wrote: > In order to separate slabs from folios, we need to convert from any page > in a slab to the slab directly without going through a page to folio > conversion first. page_slab() is a little different from other memdesc > converters we have in that it will return NULL if the page is not part > of a slab. This will be the normal style for memdesc converters in > the future. > > kfence was the only user of page_slab(), so adjust it to the new way > of working. It will need to be touched again when we separate slab > from page. +Cc KFENCE folks. > Signed-off-by: Matthew Wilcox (Oracle) Otherwise LGTM. > --- > include/linux/page-flags.h | 14 +------------- > mm/kfence/core.c | 12 ++++++++---- > mm/slab.h | 28 ++++++++++++++++------------ > 3 files changed, 25 insertions(+), 29 deletions(-) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 0091ad1986bf..6d5e44968eab 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -1048,19 +1048,7 @@ PAGE_TYPE_OPS(Table, table, pgtable) > */ > PAGE_TYPE_OPS(Guard, guard, guard) > > -FOLIO_TYPE_OPS(slab, slab) > - > -/** > - * PageSlab - Determine if the page belongs to the slab allocator > - * @page: The page to test. > - * > - * Context: Any context. > - * Return: True for slab pages, false for any other kind of page. > - */ > -static inline bool PageSlab(const struct page *page) > -{ > - return folio_test_slab(page_folio(page)); > -} > +PAGE_TYPE_OPS(Slab, slab, slab) > > #ifdef CONFIG_HUGETLB_PAGE > FOLIO_TYPE_OPS(hugetlb, hugetlb) > diff --git a/mm/kfence/core.c b/mm/kfence/core.c > index 727c20c94ac5..b16e73fd5b68 100644 > --- a/mm/kfence/core.c > +++ b/mm/kfence/core.c > @@ -612,13 +612,15 @@ static unsigned long kfence_init_pool(void) > * enters __slab_free() slow-path. > */ > for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { > + struct page *page; > struct slab *slab; > > if (!i || (i % 2)) > continue; > > - slab = page_slab(pfn_to_page(start_pfn + i)); > - __folio_set_slab(slab_folio(slab)); > + page = pfn_to_page(start_pfn + i); > + __SetPageSlab(page); > + slab = page_slab(page); > #ifdef CONFIG_MEMCG > slab->obj_exts = (unsigned long)&kfence_metadata_init[i / 2 - 1].obj_exts | > MEMCG_DATA_OBJEXTS; > @@ -665,16 +667,18 @@ static unsigned long kfence_init_pool(void) > > reset_slab: > for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { > + struct page *page; > struct slab *slab; > > if (!i || (i % 2)) > continue; > > - slab = page_slab(pfn_to_page(start_pfn + i)); > + page = pfn_to_page(start_pfn + i); > + slab = page_slab(page); > #ifdef CONFIG_MEMCG > slab->obj_exts = 0; > #endif > - __folio_clear_slab(slab_folio(slab)); > + __ClearPageSlab(page); > } > > return addr; > diff --git a/mm/slab.h b/mm/slab.h > index 078daecc7cf5..a64b9b2c8731 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -146,20 +146,24 @@ static_assert(IS_ALIGNED(offsetof(struct slab, freelist), sizeof(freelist_aba_t) > struct slab *: (struct folio *)s)) > > /** > - * page_slab - Converts from first struct page to slab. > - * @p: The first (either head of compound or single) page of slab. > + * page_slab - Converts from struct page to its slab. > + * @page: A page which may or may not belong to a slab. > * > - * A temporary wrapper to convert struct page to struct slab in situations where > - * we know the page is the compound head, or single order-0 page. > - * > - * Long-term ideally everything would work with struct slab directly or go > - * through folio to struct slab. > - * > - * Return: The slab which contains this page > + * Return: The slab which contains this page or NULL if the page does > + * not belong to a slab. This includes pages returned from large kmalloc. > */ > -#define page_slab(p) (_Generic((p), \ > - const struct page *: (const struct slab *)(p), \ > - struct page *: (struct slab *)(p))) > +static inline struct slab *page_slab(const struct page *page) > +{ > + unsigned long head; > + > + head = READ_ONCE(page->compound_head); > + if (head & 1) > + page = (struct page *)(head - 1); > + if (data_race(page->page_type >> 24) != PGTY_slab) > + page = NULL; > + > + return (struct slab *)page; > +} > > /** > * slab_page - The first struct page allocated for a slab