From f724392415b3e1ae844d2766669c0d955fe9a17b Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 18 Apr 2023 22:22:02 -0700 Subject: [PATCH] hugetlb: pte_alloc_huge() to replace huge pte_alloc_map() Some architectures can have their hugetlb pages down at the lowest PTE level: their huge_pte_alloc() using pte_alloc_map(), but without any following pte_unmap(). Since none of these arches uses CONFIG_HIGHPTE, this is not seen as a problem at present; but would become a problem if forthcoming changes were to add an rcu_read_lock() into pte_offset_map(), with the rcu_read_unlock() expected in pte_unmap(). Similarly in their huge_pte_offset(): pte_offset_kernel() is good enough for that, but it's probably less confusing if we define pte_offset_huge() along with pte_alloc_huge(). Only define them without CONFIG_HIGHPTE: so there would be a build error to signal if ever more work is needed. For ease of development, define these now for 6.4-rc1, ahead of any use: then architectures can integrate patches using them, independent from mm. Link: https://lkml.kernel.org/r/ae9e7d98-8a3a-cfd9-4762-bcddffdf96cf@google.com Signed-off-by: Hugh Dickins Reviewed-by: Mike Kravetz Cc: Muchun Song Signed-off-by: Andrew Morton --- include/linux/hugetlb.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 28703fe..cbe1e97 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -191,6 +191,23 @@ extern struct list_head huge_boot_pages; /* arch callbacks */ +#ifndef CONFIG_HIGHPTE +/* + * pte_offset_huge() and pte_alloc_huge() are helpers for those architectures + * which may go down to the lowest PTE level in their huge_pte_offset() and + * huge_pte_alloc(): to avoid reliance on pte_offset_map() without pte_unmap(). + */ +static inline pte_t *pte_offset_huge(pmd_t *pmd, unsigned long address) +{ + return pte_offset_kernel(pmd, address); +} +static inline pte_t *pte_alloc_huge(struct mm_struct *mm, pmd_t *pmd, + unsigned long address) +{ + return pte_alloc(mm, pmd) ? NULL : pte_offset_huge(pmd, address); +} +#endif + pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, unsigned long sz); /* -- 2.7.4