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[2003:d8:2f26:ba00:803:6ec5:9918:6fd]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3c0771c166bsm12920369f8f.33.2025.08.21.13.08.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Aug 2025 13:08:39 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrew Morton , Brendan Jackman , Christoph Lameter , Dennis Zhou , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, Jason Gunthorpe , Jens Axboe , Johannes Weiner , John Hubbard , kasan-dev@googlegroups.com, kvm@vger.kernel.org, "Liam R. Howlett" , Linus Torvalds , linux-arm-kernel@axis.com, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-ide@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Lorenzo Stoakes , Marek Szyprowski , Michal Hocko , Mike Rapoport , Muchun Song , netdev@vger.kernel.org, Oscar Salvador , Peter Xu , Robin Murphy , Suren Baghdasaryan , Tejun Heo , virtualization@lists.linux.dev, Vlastimil Babka , wireguard@lists.zx2c4.com, x86@kernel.org, Zi Yan Subject: [PATCH RFC 33/35] kfence: drop nth_page() usage Date: Thu, 21 Aug 2025 22:06:59 +0200 Message-ID: <20250821200701.1329277-34-david@redhat.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250821200701.1329277-1-david@redhat.com> References: <20250821200701.1329277-1-david@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ipYmNADk6jJ4ZNFwdM9hg4xsxEVXISvdUM0n80pA8cw_1755806920 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-HE-Meta: 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 9ItStirK 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 X-Rspamd-Queue-Id: 63F7920005 X-Stat-Signature: jf3axuurjkjx3a7pau3zrxpqeyqsfdg1 X-HE-Tag-Orig: 1755806923-932457 X-Rspamd-Server: rspam04 X-Rspam-User: X-HE-Tag: 1755806926-633867 X-HE-Meta: U2FsdGVkX1/7hftaDgKKsF3YLGCQuRJLV3oe2+xO8T2qMczeMI6Vl2+GLWZE9t0XcGoygEtsx8RKQTpZ3Ew9XUS1yPl8b1pepTlq+UB4sxHc9ikoPDb2LjTHjr/vg+JEoJwWvy+IwWqC8SYHUSh3eOIWUdABG3R4tc5o/g1fWaBAUMhhPhal0gt/ZXyJLsqN7WJlBo1ku4Fh5ERggeL0FO+ibshm97/O5g/ZSMG6lbfOFe4lpe97scSWa7YjUlw65uEX7XjAiun+MtN7fseriYeU3DSBrxEUb+bXwOmpJpKp9OYXNnuZDwBB9Mkl2CHnCH6g9wvx2EO3bT5rz1ufz/o3Pq3RoUkeddUvmWOpzQvSmdbqNSV8h2KeHC7z+f5L8b/uXDPPOgPsDWeo6zm6T+EVFGo7gQsnStsDzt8bP0CLSxw5joK+q8AG4PvkRiRudDQ3zLg5mHnqlJv462ayw35ES1Q5wcn0UOz0SBVs7BnD/2y7EnxIp6ciGt99jJtexnC0OPQ6p6PBcXB6gqtLBiRH6NxZqyozqzUKjp8BMjzs57nTYsgdAymLhrrciv0lqesDjbJFxWSg48oEXllygcsvi0phwFogej5KX3P/gEe27+kaDKcQjxLxc6tp63uyuPn84iBKK6Q3HAoo+rZFdpswGtMz+z9+S6TVJLdDbF+6fPNiRVR2bgBv4NU6deX8rkpW/gKgtlolg4AkaXPn6mpzfOFt4b936eBY+74sJj8z/symOk4ubLv48iNB6iKNmWAvleoDXziSqVhtj91Mm3PsntN1ctyzIe0/XyONUaqbnK8klO1+elGrvnD6qdWiXIcBtJEWeLjENv8JGe1vtd8phj4Ig4WjUCulcsYcvjIbPNJU+uZ6H/8IXRw0JFwoABixESDCMr9L03qIdzqlPQW/iTQJgZa89i+8Sf0yRqu+uDtgJCmHXlbdZf9mxHXMbtl4mJMj2xYZR3D2d/7 TbOEfnjE aT42Hxpe6Cv3fozyW7ksD5AGenVxhvFEkzbsdzROv/DZAUUbbxnhRO5bVfHhi0fs2RsZtiGKZGwDsJX9Xpo3ArZg1fxX8PLJEc+KpVvR3dnWO1Gspr+iafF09jm4JrLqa/K9c3r3O5Rrcnr/LA0Xi/xHL99TBYaexgSeUXmhVau/oELJGQdEVUB3AHLyvpv8uCrbMoRTXtSsQ65SMmbNgCvJSwVwCETOCSz21FJeFa7YTPox7MGmeHMio7SJ1/Z9nubSGAtuJ7GluOQMvyo2iJKkRRYqvs3jAnJvA8hRlH9QdakdM2+IEFMk0oM8AXTVK7gTr3eUP3s+KzHYubbZm5KXMqPLogysB/Mwqj7wh0Ud/yW+TYhWEh7dFtFL1WoID+iiUaxvzyfDCFOdUTeap5b4g4Qm8gDhrcxl14SfN2N3p9eJ1mI0lWXc3P96jsuEeoFbbUhqNZlWFT/uLOUV8Ne9JwtXbbDveNJ2K 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: We want to get rid of nth_page(), and kfence init code is the last user. Unfortunately, we might actually walk a PFN range where the pages are not contiguous, because we might be allocating an area from memblock that could span memory sections in problematic kernel configs (SPARSEMEM without SPARSEMEM_VMEMMAP). We could check whether the page range is contiguous using page_range_contiguous() and failing kfence init, or making kfence incompatible these problemtic kernel configs. Let's keep it simple and simply use pfn_to_page() by iterating PFNs. Cc: Alexander Potapenko Cc: Marco Elver Cc: Dmitry Vyukov Signed-off-by: David Hildenbrand --- mm/kfence/core.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 0ed3be100963a..793507c77f9e8 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -594,15 +594,15 @@ static void rcu_guarded_free(struct rcu_head *h) */ static unsigned long kfence_init_pool(void) { - unsigned long addr; - struct page *pages; + unsigned long addr, pfn, start_pfn, end_pfn; int i; if (!arch_kfence_init_pool()) return (unsigned long)__kfence_pool; addr = (unsigned long)__kfence_pool; - pages = virt_to_page(__kfence_pool); + start_pfn = PHYS_PFN(virt_to_phys(__kfence_pool)); + end_pfn = start_pfn + KFENCE_POOL_SIZE / PAGE_SIZE; /* * Set up object pages: they must have PGTY_slab set to avoid freeing @@ -612,12 +612,13 @@ static unsigned long kfence_init_pool(void) * fast-path in SLUB, and therefore need to ensure kfree() correctly * enters __slab_free() slow-path. */ - for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab = page_slab(nth_page(pages, i)); + for (pfn = start_pfn; pfn != end_pfn; pfn++) { + struct slab *slab; if (!i || (i % 2)) continue; + slab = page_slab(pfn_to_page(pfn)); __folio_set_slab(slab_folio(slab)); #ifdef CONFIG_MEMCG slab->obj_exts = (unsigned long)&kfence_metadata_init[i / 2 - 1].obj_exts | @@ -664,11 +665,13 @@ static unsigned long kfence_init_pool(void) return 0; reset_slab: - for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab = page_slab(nth_page(pages, i)); + for (pfn = start_pfn; pfn != end_pfn; pfn++) { + struct slab *slab; if (!i || (i % 2)) continue; + + slab = page_slab(pfn_to_page(pfn)); #ifdef CONFIG_MEMCG slab->obj_exts = 0; #endif -- 2.50.1