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-rw-r--r--mm/hugetlb.c66
1 files changed, 66 insertions, 0 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ec49d9ef1eef..418bf01a50ed 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1826,11 +1826,17 @@ static void return_unused_surplus_pages(struct hstate *h,
* is not the case is if a reserve map was changed between calls. It
* is the responsibility of the caller to notice the difference and
* take appropriate action.
+ *
+ * vma_add_reservation is used in error paths where a reservation must
+ * be restored when a newly allocated huge page must be freed. It is
+ * to be called after calling vma_needs_reservation to determine if a
+ * reservation exists.
*/
enum vma_resv_mode {
VMA_NEEDS_RESV,
VMA_COMMIT_RESV,
VMA_END_RESV,
+ VMA_ADD_RESV,
};
static long __vma_reservation_common(struct hstate *h,
struct vm_area_struct *vma, unsigned long addr,
@@ -1856,6 +1862,14 @@ static long __vma_reservation_common(struct hstate *h,
region_abort(resv, idx, idx + 1);
ret = 0;
break;
+ case VMA_ADD_RESV:
+ if (vma->vm_flags & VM_MAYSHARE)
+ ret = region_add(resv, idx, idx + 1);
+ else {
+ region_abort(resv, idx, idx + 1);
+ ret = region_del(resv, idx, idx + 1);
+ }
+ break;
default:
BUG();
}
@@ -1903,6 +1917,56 @@ static void vma_end_reservation(struct hstate *h,
(void)__vma_reservation_common(h, vma, addr, VMA_END_RESV);
}
+static long vma_add_reservation(struct hstate *h,
+ struct vm_area_struct *vma, unsigned long addr)
+{
+ return __vma_reservation_common(h, vma, addr, VMA_ADD_RESV);
+}
+
+/*
+ * This routine is called to restore a reservation on error paths. In the
+ * specific error paths, a huge page was allocated (via alloc_huge_page)
+ * and is about to be freed. If a reservation for the page existed,
+ * alloc_huge_page would have consumed the reservation and set PagePrivate
+ * in the newly allocated page. When the page is freed via free_huge_page,
+ * the global reservation count will be incremented if PagePrivate is set.
+ * However, free_huge_page can not adjust the reserve map. Adjust the
+ * reserve map here to be consistent with global reserve count adjustments
+ * to be made by free_huge_page.
+ */
+static void restore_reserve_on_error(struct hstate *h,
+ struct vm_area_struct *vma, unsigned long address,
+ struct page *page)
+{
+ if (unlikely(PagePrivate(page))) {
+ long rc = vma_needs_reservation(h, vma, address);
+
+ if (unlikely(rc < 0)) {
+ /*
+ * Rare out of memory condition in reserve map
+ * manipulation. Clear PagePrivate so that
+ * global reserve count will not be incremented
+ * by free_huge_page. This will make it appear
+ * as though the reservation for this page was
+ * consumed. This may prevent the task from
+ * faulting in the page at a later time. This
+ * is better than inconsistent global huge page
+ * accounting of reserve counts.
+ */
+ ClearPagePrivate(page);
+ } else if (rc) {
+ rc = vma_add_reservation(h, vma, address);
+ if (unlikely(rc < 0))
+ /*
+ * See above comment about rare out of
+ * memory condition.
+ */
+ ClearPagePrivate(page);
+ } else
+ vma_end_reservation(h, vma, address);
+ }
+}
+
struct page *alloc_huge_page(struct vm_area_struct *vma,
unsigned long addr, int avoid_reserve)
{
@@ -3498,6 +3562,7 @@ retry_avoidcopy:
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
out_release_all:
+ restore_reserve_on_error(h, vma, address, new_page);
put_page(new_page);
out_release_old:
put_page(old_page);
@@ -3680,6 +3745,7 @@ backout:
spin_unlock(ptl);
backout_unlocked:
unlock_page(page);
+ restore_reserve_on_error(h, vma, address, page);
put_page(page);
goto out;
}