collapse_shmem()'s xas_nomem() is very unlikely to fail, but it is
rightly given a failure path, so move the whole xas_create_range() block
up before __SetPageLocked(new_page): so that it does not need to remember
to unlock_page(new_page). Add the missing mem_cgroup_cancel_charge(),
and set (currently unused) result to SCAN_FAIL rather than SCAN_SUCCEED.
Fixes: 77da9389b9d5 ("mm: Convert collapse_shmem to XArray")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 2c5fe4f7a0c6..8e2ff195ecb3 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1329,6 +1329,20 @@ static void collapse_shmem(struct mm_struct *mm,
goto out;
}
+ /* This will be less messy when we use multi-index entries */
+ do {
+ xas_lock_irq(&xas);
+ xas_create_range(&xas);
+ if (!xas_error(&xas))
+ break;
+ xas_unlock_irq(&xas);
+ if (!xas_nomem(&xas, GFP_KERNEL)) {
+ mem_cgroup_cancel_charge(new_page, memcg, true);
+ result = SCAN_FAIL;
+ goto out;
+ }
+ } while (1);
+
__SetPageLocked(new_page);
__SetPageSwapBacked(new_page);
new_page->index = start;
@@ -1340,17 +1354,6 @@ static void collapse_shmem(struct mm_struct *mm,
* be able to map it or use it in another way until we unlock it.
*/
- /* This will be less messy when we use multi-index entries */
- do {
- xas_lock_irq(&xas);
- xas_create_range(&xas);
- if (!xas_error(&xas))
- break;
- xas_unlock_irq(&xas);
- if (!xas_nomem(&xas, GFP_KERNEL))
- goto out;
- } while (1);
-
xas_set(&xas, start);
for (index = start; index < end; index++) {
struct page *page = xas_next(&xas);
--
2.20.0.rc0.387.gc7a69e6b6c-goog
