aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorPeter Xu <peterx@redhat.com>2020-08-06 23:26:11 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-08-26 10:31:06 +0200
commit734654ae7962be55c44ff3fb0bb0652b5149cc17 (patch)
tree28527644caa218406f0ae5931d35e4b1084c3c7c
parentdcb6e6efb3298e59d90ee05c6ed33de810314892 (diff)
downloadlinux-yocto-734654ae7962be55c44ff3fb0bb0652b5149cc17.tar.gz
linux-yocto-734654ae7962be55c44ff3fb0bb0652b5149cc17.tar.bz2
linux-yocto-734654ae7962be55c44ff3fb0bb0652b5149cc17.zip
mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible
commit 75802ca66354a39ab8e35822747cd08b3384a99a upstream. This is found by code observation only. Firstly, the worst case scenario should assume the whole range was covered by pmd sharing. The old algorithm might not work as expected for ranges like (1g-2m, 1g+2m), where the adjusted range should be (0, 1g+2m) but the expected range should be (0, 2g). Since at it, remove the loop since it should not be required. With that, the new code should be faster too when the invalidating range is huge. Mike said: : With range (1g-2m, 1g+2m) within a vma (0, 2g) the existing code will only : adjust to (0, 1g+2m) which is incorrect. : : We should cc stable. The original reason for adjusting the range was to : prevent data corruption (getting wrong page). Since the range is not : always adjusted correctly, the potential for corruption still exists. : : However, I am fairly confident that adjust_range_if_pmd_sharing_possible : is only gong to be called in two cases: : : 1) for a single page : 2) for range == entire vma : : In those cases, the current code should produce the correct results. : : To be safe, let's just cc stable. Fixes: 017b1660df89 ("mm: migration: fix migration of huge PMD shared pages") Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/20200730201636.74778-1-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/hugetlb.c24
1 files changed, 10 insertions, 14 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e068c7f75a84..8a5708f31aa0 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4650,25 +4650,21 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr)
void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
unsigned long *start, unsigned long *end)
{
- unsigned long check_addr = *start;
+ unsigned long a_start, a_end;
if (!(vma->vm_flags & VM_MAYSHARE))
return;
- for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
- unsigned long a_start = check_addr & PUD_MASK;
- unsigned long a_end = a_start + PUD_SIZE;
+ /* Extend the range to be PUD aligned for a worst case scenario */
+ a_start = ALIGN_DOWN(*start, PUD_SIZE);
+ a_end = ALIGN(*end, PUD_SIZE);
- /*
- * If sharing is possible, adjust start/end if necessary.
- */
- if (range_in_vma(vma, a_start, a_end)) {
- if (a_start < *start)
- *start = a_start;
- if (a_end > *end)
- *end = a_end;
- }
- }
+ /*
+ * Intersect the range with the vma range, since pmd sharing won't be
+ * across vma after all
+ */
+ *start = max(vma->vm_start, a_start);
+ *end = min(vma->vm_end, a_end);
}
/*