diff options
| author | Punit Agrawal <punit.agrawal@arm.com> | 2017-08-02 10:37:34 +1000 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2017-08-02 10:37:34 +1000 |
| commit | 33f50e4ad20324d9062c1ad303b3ec54c15d84d0 (patch) | |
| tree | 49571d829607cd8c5dbb478ce646627cc42bc885 /mm | |
| parent | 74affe9e243473a30f0aa1bb2e1a554c7bada3e8 (diff) | |
mm/hugetlb.c: make huge_pte_offset() consistent and document behaviour
When walking the page tables to resolve an address that points to
!p*d_present() entry, huge_pte_offset() returns inconsistent values
depending on the level of page table (PUD or PMD).
It returns NULL in the case of a PUD entry while in the case of a PMD
entry, it returns a pointer to the page table entry.
A similar inconsitency exists when handling swap entries - returns NULL
for a PUD entry while a pointer to the pte_t is retured for the PMD entry.
Update huge_pte_offset() to make the behaviour consistent - return NULL in
the case of p*d_none() and a pointer to the pte_t for hugepage or swap
entries.
Document the behaviour to clarify the expected behaviour of this function.
This is to set clear semantics for architecture specific implementations
of huge_pte_offset().
Link: http://lkml.kernel.org/r/20170725154114.24131-2-punit.agrawal@arm.com
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/hugetlb.c | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a1a0ac0ad6f6..3c97ea275332 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4600,6 +4600,13 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, return pte; } +/* + * huge_pte_offset() - Walk the page table to resolve the hugepage + * entry at address @addr + * + * Return: Pointer to page table or swap entry (PUD or PMD) for address @addr + * or NULL if the entry is p*d_none(). + */ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr, unsigned long sz) { @@ -4614,13 +4621,22 @@ pte_t *huge_pte_offset(struct mm_struct *mm, p4d = p4d_offset(pgd, addr); if (!p4d_present(*p4d)) return NULL; + pud = pud_offset(p4d, addr); - if (!pud_present(*pud)) + if (pud_none(*pud)) return NULL; - if (pud_huge(*pud)) + /* hugepage or swap? */ + if (pud_huge(*pud) || !pud_present(*pud)) return (pte_t *)pud; + pmd = pmd_offset(pud, addr); - return (pte_t *) pmd; + if (pmd_none(*pmd)) + return NULL; + /* hugepage or swap? */ + if (pmd_huge(*pmd) || !pmd_present(*pmd)) + return (pte_t *) pmd; + + return NULL; } #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */ |