From: Li Xinhai <lixinhai.lxh@xxxxxxxxx>
Subject: mm/mempolicy.c: check range first in queue_pages_test_walk
Patch series "mm: Fix checking unmapped holes for mbind", v4.
This patchset fix checking unmapped holes for mbind().
First patch makes sure the vma been correctly tracked in .test_walk(),
so each time when .test_walk() is called, the neighborhood of two vma
is correct.
Current problem is that the !vma_migratable() check could cause return
immediately without update tracking to vma.
Second patch fix the inconsistent report of EFAULT when mbind() is
called for MPOL_DEFAULT and non MPOL_DEFAULT cases, so application do
not need to have workaround code to handle this special behavior.
Currently there are two problems, one is that the .test_walk() can not
know there is hole at tail side of range, because .test_walk() only
call for vma not for hole. The other one is that mbind_range() checks
for hole at head side of range but do not consider the
MPOL_MF_DISCONTIG_OK flag as done in .test_walk().
This patch (of 2):
Checking unmapped hole and updating the previous vma must be handled
first, otherwise the unmapped hole could be calculated from a wrong
previous vma.
Several commits were relevant to this error:
commit 6f4576e3687b
("mempolicy: apply page table walker on queue_pages_range()"),
This commit was correct, the VM_PFNMAP check was after updating previous
vma
commit 48684a65b4e3
(mm: pagewalk: fix misbehavior of walk_page_range for vma(VM_PFNMAP)),
This commit added VM_PFNMAP check before updating previous vma. Then,
there were two VM_PFNMAP check did same thing twice.
commit acda0c334028
(mm/mempolicy.c: get rid of duplicated check for vma(VM_PFNMAP) in queue_page
s_range()),
This commit tried to fix the duplicated VM_PFNMAP check, but it wrongly
removed the one which was after updating vma.
Link: http://lkml.kernel.org/r/1573218104-11021-2-git-send-email-lixinhai.lxh@xxxxxxxxx
Fixes: acda0c334028 (mm/mempolicy.c: get rid of duplicated check for vma(VM_PFNMAP) in queue_pages_range())
Signed-off-by: Li Xinhai <lixinhai.lxh@xxxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: linux-man <linux-man@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mempolicy.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
--- a/mm/mempolicy.c~mm-check-range-first-in-queue_pages_test_walk
+++ a/mm/mempolicy.c
@@ -618,6 +618,16 @@ static int queue_pages_test_walk(unsigne
unsigned long endvma = vma->vm_end;
unsigned long flags = qp->flags;
+ /* range check first */
+ if (!(flags & MPOL_MF_DISCONTIG_OK)) {
+ if (!vma->vm_next && vma->vm_end < end)
+ return -EFAULT;
+ if (qp->prev && qp->prev->vm_end < vma->vm_start)
+ return -EFAULT;
+ }
+
+ qp->prev = vma;
+
/*
* Need check MPOL_MF_STRICT to return -EIO if possible
* regardless of vma_migratable
@@ -631,15 +641,6 @@ static int queue_pages_test_walk(unsigne
if (vma->vm_start > start)
start = vma->vm_start;
- if (!(flags & MPOL_MF_DISCONTIG_OK)) {
- if (!vma->vm_next && vma->vm_end < end)
- return -EFAULT;
- if (qp->prev && qp->prev->vm_end < vma->vm_start)
- return -EFAULT;
- }
-
- qp->prev = vma;
-
if (flags & MPOL_MF_LAZY) {
/* Similar to task_numa_work, skip inaccessible VMAs */
if (!is_vm_hugetlb_page(vma) &&
_
