summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--mm/memory.c24
1 files changed, 21 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c
index db6590c8cc11..df84668807ad 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,26 @@ no_page_table:
return page;
}
+/* Can we do the FOLL_ANON optimization? */
+static inline int use_zero_page(struct vm_area_struct *vma)
+{
+ /*
+ * We don't want to optimize FOLL_ANON for make_pages_present()
+ * when it tries to page in a VM_LOCKED region. As to VM_SHARED,
+ * we want to get the page from the page tables to make sure
+ * that we serialize and update with any other user of that
+ * mapping.
+ */
+ if (vma->vm_flags & (VM_LOCKED | VM_SHARED))
+ return 0;
+ /*
+ * And if we have a fault or a nopfn routine, it's not an
+ * anonymous region.
+ */
+ return !vma->vm_ops ||
+ (!vma->vm_ops->fault && !vma->vm_ops->nopfn);
+}
+
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, int len, int write, int force,
struct page **pages, struct vm_area_struct **vmas)
@@ -1063,9 +1083,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
foll_flags = FOLL_TOUCH;
if (pages)
foll_flags |= FOLL_GET;
- if (!write && !(vma->vm_flags & VM_LOCKED) &&
- (!vma->vm_ops || (!vma->vm_ops->nopage &&
- !vma->vm_ops->fault)))
+ if (!write && use_zero_page(vma))
foll_flags |= FOLL_ANON;
do {