Huge tmpfs testing reminds us that there is no __GFP_ZERO in the gfp
flags khugepaged uses to allocate a huge page - in all common cases it
would just be a waste of effort - so collapse_shmem() must remember to
clear out any holes that it instantiates.
The obvious place to do so, where they are put into the page cache tree,
is not a good choice: because interrupts are disabled there. Leave it
until further down, once success is assured, where the other pages are
copied (before setting PageUptodate).
Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 4.8+
---
mm/khugepaged.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 65e82f665c7c..1c402d33547e 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1467,7 +1467,12 @@ static void collapse_shmem(struct mm_struct *mm,
* Replacing old pages with new one has succeeded, now we
* need to copy the content and free the old pages.
*/
+ index = start;
list_for_each_entry_safe(page, tmp, &pagelist, lru) {
+ while (index < page->index) {
+ clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ index++;
+ }
copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
page);
list_del(&page->lru);
@@ -1477,6 +1482,11 @@ static void collapse_shmem(struct mm_struct *mm,
ClearPageActive(page);
ClearPageUnevictable(page);
put_page(page);
+ index++;
+ }
+ while (index < end) {
+ clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ index++;
}
local_irq_disable();
--
2.20.0.rc0.387.gc7a69e6b6c-goog
