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Thu, 28 Aug 2025 01:43:52 -0700 (PDT) MIME-Version: 1.0 References: <20250827220141.262669-1-david@redhat.com> <20250827220141.262669-35-david@redhat.com> In-Reply-To: <20250827220141.262669-35-david@redhat.com> From: Marco Elver Date: Thu, 28 Aug 2025 10:43:16 +0200 X-Gm-Features: Ac12FXwMzUnIHp_v7uH0kV3Hu6ram9vqgPmCMZ3TyuNNAlhDfe6K8rTgx1FpO8k Message-ID: Subject: Re: [PATCH v1 34/36] kfence: drop nth_page() usage To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Alexander Potapenko , 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 Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 615DF120002 X-Stat-Signature: b8kykdzgtonyshe8izwq3ykqmn1ixd7z X-HE-Tag: 1756370634-34177 X-HE-Meta: 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 xC5XhZ9w AShkCY/yFiPVotB8q5AZrpA4Rtc+PZooj7AO6ji7dq/fw/hsyz9wYrNAmA/AYRVps3OFfc/NTh5WQpeaBHO7oLRyFw/gUS/DrTN9zprtQmn4yCNDU3TtHcCm98sqOUs0v0RxAzW3upYZyfbe6KqVZVS70xwZ5mfluOqMMOTzuA0CD8SizNgDF/eWrIyNA7Szs4n7cnNi7eo3qlQfoFwpBPJNwuHKuLEKZTW5xyl6czZ1DTL74FX9qPItH16t0wHWYnNi/JNqh/h8mDpCHGRVrDDdtXopVzNmP1Aqzp+q2xjltJ/r1fN/Z88EQFCevMHZ0n0Kmx0hlx88j/E4= 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 Thu, 28 Aug 2025 at 00:11, 'David Hildenbrand' via kasan-dev wrote: > > 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 Reviewed-by: Marco Elver Thanks. > --- > 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 > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com. > To view this discussion visit https://groups.google.com/d/msgid/kasan-dev/20250827220141.262669-35-david%40redhat.com.