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[2003:d8:2f31:700:3851:c66a:b6b9:3490]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3a568a54a36sm14542075f8f.15.2025.06.17.08.43.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Jun 2025 08:43:49 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, David Hildenbrand , Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Alistair Popple , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Zi Yan , Baolin Wang , Lorenzo Stoakes , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato Subject: [PATCH RFC 01/14] mm/memory: drop highest_memmap_pfn sanity check in vm_normal_page() Date: Tue, 17 Jun 2025 17:43:32 +0200 Message-ID: <20250617154345.2494405-2-david@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250617154345.2494405-1-david@redhat.com> References: <20250617154345.2494405-1-david@redhat.com> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: GoNmDajC02YpUbcws4RsxxuOsu5-rH6L8AGwopNjg0Y_1750175030 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true In 2009, we converted a VM_BUG_ON(!pfn_valid(pfn)) to the current highest_memmap_pfn sanity check in commit 22b31eec63e5 ("badpage: vm_normal_page use print_bad_pte"), because highest_memmap_pfn was readily available. Nowadays, this is the last remaining highest_memmap_pfn user, and this sanity check is not really triggering ... frequently. Let's convert it to VM_WARN_ON_ONCE(!pfn_valid(pfn)), so we can simplify and get rid of highest_memmap_pfn. Checking for pfn_to_online_page() might be even better, but it would not handle ZONE_DEVICE properly. Do the same in vm_normal_page_pmd(), where we don't even report a problem at all ... What might be better in the future is having a runtime option like page-table-check to enable such checks dynamically on-demand. Something for the future. Signed-off-by: David Hildenbrand --- mm/memory.c | 15 +++------------ 1 file changed, 3 insertions(+), 12 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 0163d127cece9..188b84ebf479a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -590,7 +590,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) { if (likely(!pte_special(pte))) - goto check_pfn; + goto out; if (vma->vm_ops && vma->vm_ops->find_special_page) return vma->vm_ops->find_special_page(vma, addr); if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)) @@ -608,9 +608,6 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, if (vma->vm_flags & VM_MIXEDMAP) { if (!pfn_valid(pfn)) return NULL; - if (is_zero_pfn(pfn)) - return NULL; - goto out; } else { unsigned long off; off = (addr - vma->vm_start) >> PAGE_SHIFT; @@ -624,17 +621,12 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, if (is_zero_pfn(pfn)) return NULL; -check_pfn: - if (unlikely(pfn > highest_memmap_pfn)) { - print_bad_pte(vma, addr, pte, NULL); - return NULL; - } - /* * NOTE! We still have PageReserved() pages in the page tables. * eg. VDSO mappings can cause them to exist. */ out: + VM_WARN_ON_ONCE(!pfn_valid(pfn)); VM_WARN_ON_ONCE(is_zero_pfn(pfn)); return pfn_to_page(pfn); } @@ -676,14 +668,13 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr, if (is_huge_zero_pmd(pmd)) return NULL; - if (unlikely(pfn > highest_memmap_pfn)) - return NULL; /* * NOTE! We still have PageReserved() pages in the page tables. * eg. VDSO mappings can cause them to exist. */ out: + VM_WARN_ON_ONCE(!pfn_valid(pfn)); return pfn_to_page(pfn); } -- 2.49.0