The patch titled
Subject: mm: pagewalk: fix misbehavior of walk_page_range for vma(VM_PFNMAP)
has been added to the -mm tree. Its filename is
mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: mm: pagewalk: fix misbehavior of walk_page_range for vma(VM_PFNMAP)
walk_page_range() silently skips vma having VM_PFNMAP set, which leads to
undesirable behaviour at client end (who called walk_page_range). For
example for pagemap_read(), when no callbacks are called against VM_PFNMAP
vma, pagemap_read() may prepare pagemap data for next virtual address
range at wrong index. That could confuse and/or break userspace
applications.
This patch avoid this misbehavior caused by vma(VM_PFNMAP) like follows:
- for pagemap_read() which has its own ->pte_hole(), call the ->pte_hole()
over vma(VM_PFNMAP),
- for clear_refs and queue_pages which have their own ->tests_walk,
just return 1 and skip vma(VM_PFNMAP). This is no problem because
these are not interested in hole regions,
- for other callers, just skip the vma(VM_PFNMAP) as a default behavior.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Shiraz Hashim <shashim@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 3 +++
mm/mempolicy.c | 3 +++
mm/pagewalk.c | 21 +++++++++++++--------
3 files changed, 19 insertions(+), 8 deletions(-)
diff -puN fs/proc/task_mmu.c~mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling
+++ a/fs/proc/task_mmu.c
@@ -806,6 +806,9 @@ static int clear_refs_test_walk(unsigned
struct clear_refs_private *cp = walk->private;
struct vm_area_struct *vma = walk->vma;
+ if (vma->vm_flags & VM_PFNMAP)
+ return 1;
+
/*
* Writing 1 to /proc/pid/clear_refs affects all pages.
* Writing 2 to /proc/pid/clear_refs only affects anonymous pages.
diff -puN mm/mempolicy.c~mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling mm/mempolicy.c
--- a/mm/mempolicy.c~mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling
+++ a/mm/mempolicy.c
@@ -591,6 +591,9 @@ static int queue_pages_test_walk(unsigne
unsigned long endvma = vma->vm_end;
unsigned long flags = qp->flags;
+ if (vma->vm_flags & VM_PFNMAP)
+ return 1;
+
if (endvma > end)
endvma = end;
if (vma->vm_start > start)
diff -puN mm/pagewalk.c~mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling mm/pagewalk.c
--- a/mm/pagewalk.c~mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling
+++ a/mm/pagewalk.c
@@ -35,7 +35,7 @@ static int walk_pmd_range(pud_t *pud, un
do {
again:
next = pmd_addr_end(addr, end);
- if (pmd_none(*pmd)) {
+ if (pmd_none(*pmd) || !walk->vma) {
if (walk->pte_hole)
err = walk->pte_hole(addr, next, walk);
if (err)
@@ -165,9 +165,6 @@ static int walk_hugetlb_range(unsigned l
* or skip it via the returned value. Return 0 if we do walk over the
* current vma, and return 1 if we skip the vma. Negative values means
* error, where we abort the current walk.
- *
- * Default check (only VM_PFNMAP check for now) is used when the caller
- * doesn't define test_walk() callback.
*/
static int walk_page_test(unsigned long start, unsigned long end,
struct mm_walk *walk)
@@ -178,11 +175,19 @@ static int walk_page_test(unsigned long
return walk->test_walk(start, end, walk);
/*
- * Do not walk over vma(VM_PFNMAP), because we have no valid struct
- * page backing a VM_PFNMAP range. See also commit a9ff785e4437.
+ * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
+ * range, so we don't walk over it as we do for normal vmas. However,
+ * Some callers are interested in handling hole range and they don't
+ * want to just ignore any single address range. Such users certainly
+ * define their ->pte_hole() callbacks, so let's delegate them to handle
+ * vma(VM_PFNMAP).
*/
- if (vma->vm_flags & VM_PFNMAP)
- return 1;
+ if (vma->vm_flags & VM_PFNMAP) {
+ int err = 1;
+ if (walk->pte_hole)
+ err = walk->pte_hole(start, end, walk);
+ return err ? err : 1;
+ }
return 0;
}
_
Patches currently in -mm which might be from n-horiguchi@xxxxxxxxxxxxx are
mm-pagewalk-call-pte_hole-for-vm_pfnmap-during-walk_page_range.patch
mm-add-kpf_zero_page-flag-for-proc-kpageflags.patch
mm-hugetlb-reduce-arch-dependent-code-around-follow_huge_.patch
mm-hugetlb-pmd_huge-returns-true-for-non-present-hugepage.patch
mm-hugetlb-take-page-table-lock-in-follow_huge_pmd.patch
mm-hugetlb-fix-getting-refcount-0-page-in-hugetlb_fault.patch
mm-hugetlb-add-migration-hwpoisoned-entry-check-in-hugetlb_change_protection.patch
mm-hugetlb-add-migration-entry-check-in-__unmap_hugepage_range.patch
mm-hugetlb-fix-suboptimal-migration-hwpoisoned-entry-check.patch
mm-hugetlb-cleanup-and-rename-is_hugetlb_entry_migrationhwpoisoned.patch
mm-pagewalk-remove-pgd_entry-and-pud_entry.patch
pagewalk-improve-vma-handling.patch
pagewalk-add-walk_page_vma.patch
smaps-remove-mem_size_stats-vma-and-use-walk_page_vma.patch
clear_refs-remove-clear_refs_private-vma-and-introduce-clear_refs_test_walk.patch
pagemap-use-walk-vma-instead-of-calling-find_vma.patch
numa_maps-fix-typo-in-gather_hugetbl_stats.patch
numa_maps-remove-numa_maps-vma.patch
memcg-cleanup-preparation-for-page-table-walk.patch
arch-powerpc-mm-subpage-protc-use-walk-vma-and-walk_page_vma.patch
mempolicy-apply-page-table-walker-on-queue_pages_range.patch
mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling.patch
mm-proc-pid-clear_refs-avoid-split_huge_page.patch
mincore-apply-page-table-walker-on-do_mincore.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
