Currently if copy_nonpresent_pte() returns a non-zero value it is
assumed to be a swap entry which requires further processing outside the
loop in copy_pte_range() after dropping locks. This prevents other
values being returned to signal conditions such as failure which a
subsequent change requires.
Instead make copy_nonpresent_pte() return an error code if further
processing is required and read the value for the swap entry in the main
loop under the ptl.
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
---
v9:
New for v9 to allow device exclusive handling to occur in
copy_nonpresent_pte().
---
mm/memory.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 2fb455c365c2..e061cfa18c11 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -718,7 +718,7 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
if (likely(!non_swap_entry(entry))) {
if (swap_duplicate(entry) < 0)
- return entry.val;
+ return -EAGAIN;
/* make sure dst_mm is on swapoff's mmlist. */
if (unlikely(list_empty(&dst_mm->mmlist))) {
@@ -974,11 +974,13 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
continue;
}
if (unlikely(!pte_present(*src_pte))) {
- entry.val = copy_nonpresent_pte(dst_mm, src_mm,
- dst_pte, src_pte,
- src_vma, addr, rss);
- if (entry.val)
+ ret = copy_nonpresent_pte(dst_mm, src_mm,
+ dst_pte, src_pte,
+ src_vma, addr, rss);
+ if (ret == -EAGAIN) {
+ entry = pte_to_swp_entry(*src_pte);
break;
+ }
progress += 8;
continue;
}
--
2.20.1
