[PATCH 3/7] khugepaged: Drain LRU add pagevec to get rid of extra pins

Kirill A. Shutemov
2020-03-27T17:06:08Z

__collapse_huge_page_isolate() may fail due to extra pin in the LRU add
pagevec. It's petty common for swapin case: we swap in pages just to
fail due to the extra pin.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/khugepaged.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 14d7afc90786..39e0994abeb8 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -585,11 +585,19 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
* The page must only be referenced by the scanned process
* and page swap cache.
*/
+ if (page_count(page) != 1 + PageSwapCache(page)) {
+ /*
+ * Drain pagevec and retry just in case we can get rid
+ * of the extra pin, like in swapin case.
+ */
+ lru_add_drain();
+ }
if (page_count(page) != 1 + PageSwapCache(page)) {
unlock_page(page);
result = SCAN_PAGE_COUNT;
goto out;
}
+
if (pte_write(pteval)) {
writable = true;
} else {
--
2.26.0