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pagewalk: improve vma handling

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Current implementation of page table walker has a fundamental problem in
vma handling, which started when we tried to handle vma(VM_HUGETLB).
Because it's done in pgd loop, considering vma boundary makes code
complicated and bug-prone.

From the users viewpoint, some user checks some vma-related condition to
determine whether the user really does page walk over the vma.

In order to solve these, this patch moves vma check outside pgd loop and
introduce a new callback ->test_walk().

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Naoya Horiguchi
2015-02-11 15:27:37 -08:00
committed by Linus Torvalds
parent 0b1fbfe500
commit fafaa4264e
2 changed files with 129 additions and 92 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
include/linux/mm.h
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@@ -1171,10 +1171,16 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
* @pte_entry: if set, called for each non-empty PTE (4th-level) entry
* @pte_hole: if set, called for each hole at all levels
* @hugetlb_entry: if set, called for each hugetlb entry
* *Caution*: The caller must hold mmap_sem() if @hugetlb_entry
* is used.
* @test_walk: caller specific callback function to determine whether
* we walk over the current vma or not. A positive returned
* value means "do page table walk over the current vma,"
* and a negative one means "abort current page table walk
* right now." 0 means "skip the current vma."
* @mm: mm_struct representing the target process of page table walk
* @vma: vma currently walked (NULL if walking outside vmas)
* @private: private data for callbacks' usage
*
* (see walk_page_range for more details)
* (see the comment on walk_page_range() for more details)
*/
struct mm_walk {
int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
@@ -1186,7 +1192,10 @@ struct mm_walk {
int (*hugetlb_entry)(pte_t *pte, unsigned long hmask,
unsigned long addr, unsigned long next,
struct mm_walk *walk);
int (*test_walk)(unsigned long addr, unsigned long next,
struct mm_walk *walk);
struct mm_struct *mm;
struct vm_area_struct *vma;
void *private;
};