diff mbox series

[v7,13/14] mm,hwpoison: double-check page count in __get_any_page()

Message ID 20200922135650.1634-14-osalvador@suse.de (mailing list archive)
State New, archived
Headers show
Series HWPOISON: soft offline rework | expand

Commit Message

Oscar Salvador Sept. 22, 2020, 1:56 p.m. UTC 
From: Naoya Horiguchi <naoya.horiguchi@nec.com>

Soft offlining could fail with EIO due to the race condition with hugepage
migration.  This issuse became visible due to the change by previous patch
that makes soft offline handler take page refcount by its own.  We have no
way to directly pin zero refcount page, and the page considered as a zero
refcount page could be allocated just after the first check.

This patch adds the second check to find the race and gives us chance to
handle it more reliably.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reported-by: Qian Cai <cai@lca.pw>
---
 mm/memory-failure.c | 6 ++++++
 1 file changed, 6 insertions(+)
diff mbox series

Patch

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 963fd9af23ab..46b1821d2817 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1707,6 +1707,9 @@  static int __get_any_page(struct page *p, unsigned long pfn, int flags)
 		} else if (is_free_buddy_page(p)) {
 			pr_info("%s: %#lx free buddy page\n", __func__, pfn);
 			ret = 0;
+		} else if (page_count(p)) {
+			/* raced with allocation */
+			ret = -EBUSY;
 		} else {
 			pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
 				__func__, pfn, p->flags);
@@ -1723,6 +1726,9 @@  static int get_any_page(struct page *page, unsigned long pfn, int flags)
 {
 	int ret = __get_any_page(page, pfn, flags);
 
+	if (ret == -EBUSY)
+		ret = __get_any_page(page, pfn, flags);
+
 	if (ret == 1 && !PageHuge(page) &&
 	    !PageLRU(page) && !__PageMovable(page)) {
 		/*