The patch titled
Subject: mm: pagewalk: fix misbehavior of walk_page_range for vma(VM_PFNMAP)
has been removed from the -mm tree. Its filename was
mm-pagewalk-fix-misbehavior-of-walk_page_range-for-vmavm_pfnmap-re-pagewalk-improve-vma-handling.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
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
origin.patch
mm-hwpoison-drop-lru_add_drain_all-in-__soft_offline_page.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
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