set_hwpoison_free_buddy_page() could fail, then the target page is
finally not isolated, so it's better to report -EBUSY for userspace
to know the failure and chance of retry.
And for consistency, this patch moves set_hwpoison_free_buddy_page()
in unmap_and_move() to __soft_offline_page().
Fixes: 6bc9b56433b7 ("mm: fix race on soft-offlining free huge pages")
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
mm/memory-failure.c | 15 ++++++++++++---
mm/migrate.c | 9 ---------
2 files changed, 12 insertions(+), 12 deletions(-)
diff --git v4.19-mmotm-2018-10-30-16-08/mm/memory-failure.c v4.19-mmotm-2018-10-30-16-08_patched/mm/memory-failure.c
index 9f09bf3..11e283e 100644
--- v4.19-mmotm-2018-10-30-16-08/mm/memory-failure.c
+++ v4.19-mmotm-2018-10-30-16-08_patched/mm/memory-failure.c
@@ -1719,14 +1719,18 @@ static int soft_offline_huge_page(struct page *page, int flags)
/*
* We set PG_hwpoison only when the migration source hugepage
* was successfully dissolved, because otherwise hwpoisoned
- * hugepage remains on free hugepage list, then userspace will
- * find it as SIGBUS by allocation failure. That's not expected
- * in soft-offlining.
+ * hugepage remains on free hugepage list. The allocator ignores
+ * such a hwpoisoned page so it's never allocated, but it could
+ * kill a process because of no-memory rather than hwpoison.
+ * Soft-offline never impacts the userspace, so this is
+ * undesired.
*/
ret = dissolve_free_huge_page(page);
if (!ret) {
if (set_hwpoison_free_buddy_page(page))
num_poisoned_pages_inc();
+ else
+ ret = -EBUSY;
}
}
return ret;
@@ -1804,6 +1808,11 @@ static int __soft_offline_page(struct page *page, int flags)
pfn, ret, page->flags, &page->flags);
if (ret > 0)
ret = -EIO;
+ } else {
+ if (set_hwpoison_free_buddy_page(page))
+ num_poisoned_pages_inc();
+ else
+ ret = -EBUSY;
}
} else {
pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx (%pGp)\n",
diff --git v4.19-mmotm-2018-10-30-16-08/mm/migrate.c v4.19-mmotm-2018-10-30-16-08_patched/mm/migrate.c
index f7e4bfd..1742372 100644
--- v4.19-mmotm-2018-10-30-16-08/mm/migrate.c
+++ v4.19-mmotm-2018-10-30-16-08_patched/mm/migrate.c
@@ -1199,15 +1199,6 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
*/
if (rc == MIGRATEPAGE_SUCCESS) {
put_page(page);
- if (reason == MR_MEMORY_FAILURE) {
- /*
- * Set PG_HWPoison on just freed page
- * intentionally. Although it's rather weird,
- * it's how HWPoison flag works at the moment.
- */
- if (set_hwpoison_free_buddy_page(page))
- num_poisoned_pages_inc();
- }
} else {
if (rc != -EAGAIN) {
if (likely(!__PageMovable(page))) {
--
2.7.0
