walk_page_range_novma() can be used to walk page tables or the kernel or for firmware. These page tables may contain entries that are not backed by a struct page and so it isn't (in general) possible to take the PTE lock for the pte_entry() callback. So update walk_pte_range() to only take the lock when no_vma==false and add a comment explaining the difference to walk_page_range_novma(). Signed-off-by: Steven Price <steven.price@xxxxxxx> --- mm/pagewalk.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/mm/pagewalk.c b/mm/pagewalk.c index efa464cf079b..1b9a3ba24c51 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -10,9 +10,10 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, pte_t *pte; int err = 0; const struct mm_walk_ops *ops = walk->ops; - spinlock_t *ptl; + spinlock_t *uninitialized_var(ptl); - pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + pte = walk->no_vma ? pte_offset_map(pmd, addr) : + pte_offset_map_lock(walk->mm, pmd, addr, &ptl); for (;;) { err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk); if (err) @@ -23,7 +24,9 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, pte++; } - pte_unmap_unlock(pte, ptl); + if (!walk->no_vma) + spin_unlock(ptl); + pte_unmap(pte); return err; } @@ -383,6 +386,12 @@ int walk_page_range(struct mm_struct *mm, unsigned long start, return err; } +/* + * Similar to walk_page_range() but can walk any page tables even if they are + * not backed by VMAs. Because 'unusual' entries may be walked this function + * will also not lock the PTEs for the pte_entry() callback. This is useful for + * walking the kernel pages tables or page tables for firmware. + */ int walk_page_range_novma(struct mm_struct *mm, unsigned long start, unsigned long end, const struct mm_walk_ops *ops, void *private) -- 2.20.1