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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, 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 v2 35/37] kfence: drop nth_page() usage Date: Mon, 1 Sep 2025 17:03:56 +0200 Message-ID: <20250901150359.867252-36-david@redhat.com> In-Reply-To: <20250901150359.867252-1-david@redhat.com> References: <20250901150359.867252-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 1E0131C0003 X-Stat-Signature: o7o3atxxba1b334jt9is5z9nnnrxzyoe X-Rspam-User: X-HE-Tag: 1756739632-405339 X-HE-Meta: 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 5ReZ6+DM /kXLFhPLj3R+eqczCM/80kFGbfiuEfq9JC2KVgl1SrdiQVEcno46rH4b4QeLZlZA3Qt3tPCP3bDNacIXouY0i4jEP/aefZImXY2Ue82ZfYzv/QWwOdGLNiFBj/FHgHmuLW4Y3z5kQrK5yqUaNeuZ0GTgGLOLhy/NrANBvfvROlEGLvAifElJezJSdAA/LqIw9TOSDBorTqsXtCJVw5OUTGlA3Xd3elWL/PDWHbPM/DdHDRDQT1NedMlwQYxBkfUiqikYqtX10PnqgL6gsmX6M/HgYAx3XfSOcShQRUzRZhAME+quNSt5hScr0yGV7S78ztgTyWhsZSQ9pNCAAumV0zDPa84xcLk3Sx0MlL5VqzfIXXMUfekLzfexgxwaxQsElY3UgKc+HY/N15Erm3YMVXoJA2kHN7nMarxko9KvCUilsgbY= 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. Reviewed-by: Marco Elver Reviewed-by: Lorenzo Stoakes Cc: Alexander Potapenko Cc: Dmitry Vyukov Signed-off-by: David Hildenbrand --- mm/kfence/core.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 0ed3be100963a..727c20c94ac59 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -594,15 +594,14 @@ 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, start_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)); /* * Set up object pages: they must have PGTY_slab set to avoid freeing @@ -613,11 +612,12 @@ static unsigned long kfence_init_pool(void) * enters __slab_free() slow-path. */ for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab = page_slab(nth_page(pages, i)); + struct slab *slab; if (!i || (i % 2)) continue; + slab = page_slab(pfn_to_page(start_pfn + i)); __folio_set_slab(slab_folio(slab)); #ifdef CONFIG_MEMCG slab->obj_exts = (unsigned long)&kfence_metadata_init[i / 2 - 1].obj_exts | @@ -665,10 +665,12 @@ static unsigned long kfence_init_pool(void) reset_slab: for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab = page_slab(nth_page(pages, i)); + struct slab *slab; if (!i || (i % 2)) continue; + + slab = page_slab(pfn_to_page(start_pfn + i)); #ifdef CONFIG_MEMCG slab->obj_exts = 0; #endif -- 2.50.1