Let's reduce the code duplication and factor out the non-pte/pmd related magic into vm_normal_page_pfn().
To keep it simpler, check the pfn against both zero folios. We could optimize this, but as it's only for the !CONFIG_ARCH_HAS_PTE_SPECIAL case, it's not a compelling micro-optimization. With CONFIG_ARCH_HAS_PTE_SPECIAL we don't have to check anything else, really. It's a good question if we can even hit the !CONFIG_ARCH_HAS_PTE_SPECIAL scenario in the PMD case in practice: but doesn't really matter, as it's now all unified in vm_normal_page_pfn(). While at it, add a check that pmd_special() is really only set where we would expect it. No functional change intended. Signed-off-by: David Hildenbrand <[email protected]> --- mm/memory.c | 104 +++++++++++++++++++++++----------------------------- 1 file changed, 46 insertions(+), 58 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index b6c069f4ad11f..3d3fa01cd217e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -536,6 +536,46 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr, add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); } +/* Called only if the page table entry is not marked special. */ +static inline struct page *vm_normal_page_pfn(struct vm_area_struct *vma, + unsigned long addr, unsigned long pfn) +{ + /* + * With CONFIG_ARCH_HAS_PTE_SPECIAL, any special page table mappings + * (incl. shared zero folios) are marked accordingly. + */ + if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) + goto normal_page; + + if (unlikely(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))) { + if (vma->vm_flags & VM_MIXEDMAP) { + /* If it has a "struct page", it's "normal". */ + if (!pfn_valid(pfn)) + return NULL; + } else { + unsigned long off = (addr - vma->vm_start) >> PAGE_SHIFT; + + /* Only CoW'ed anon folios are "normal". */ + if (pfn == vma->vm_pgoff + off) + return NULL; + if (!is_cow_mapping(vma->vm_flags)) + return NULL; + } + } + + if (is_zero_pfn(pfn) || is_huge_zero_pfn(pfn)) + return NULL; + +normal_page: + /* + * NOTE! We still have PageReserved() pages in the page tables. + * For example, VDSO mappings can cause them to exist. + */ + VM_WARN_ON_ONCE(!pfn_valid(pfn)); + VM_WARN_ON_ONCE(is_zero_pfn(pfn) || is_huge_zero_pfn(pfn)); + return pfn_to_page(pfn); +} + /* * vm_normal_page -- This function gets the "struct page" associated with a pte. * @@ -591,9 +631,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, { unsigned long pfn = pte_pfn(pte); - if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) { - if (likely(!pte_special(pte))) - goto out; + if (unlikely(pte_special(pte))) { 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)) @@ -604,34 +642,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, print_bad_pte(vma, addr, pte, NULL); return NULL; } - - /* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */ - - if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) { - if (vma->vm_flags & VM_MIXEDMAP) { - if (!pfn_valid(pfn)) - return NULL; - } else { - unsigned long off; - off = (addr - vma->vm_start) >> PAGE_SHIFT; - if (pfn == vma->vm_pgoff + off) - return NULL; - if (!is_cow_mapping(vma->vm_flags)) - return NULL; - } - } - - if (is_zero_pfn(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)); - VM_WARN_ON_ONCE(is_zero_pfn(pfn)); - return pfn_to_page(pfn); + return vm_normal_page_pfn(vma, addr, pfn); } struct folio *vm_normal_folio(struct vm_area_struct *vma, unsigned long addr, @@ -650,35 +661,12 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr, { unsigned long pfn = pmd_pfn(pmd); - /* Currently it's only used for huge pfnmaps */ - if (unlikely(pmd_special(pmd))) + if (unlikely(pmd_special(pmd))) { + VM_WARN_ON_ONCE(!(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)) && + !is_huge_zero_pfn(pfn)); return NULL; - - if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) { - if (vma->vm_flags & VM_MIXEDMAP) { - if (!pfn_valid(pfn)) - return NULL; - goto out; - } else { - unsigned long off; - off = (addr - vma->vm_start) >> PAGE_SHIFT; - if (pfn == vma->vm_pgoff + off) - return NULL; - if (!is_cow_mapping(vma->vm_flags)) - return NULL; - } } - - if (is_huge_zero_pfn(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); + return vm_normal_page_pfn(vma, addr, pfn); } struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma, -- 2.49.0
