The patch titled
Subject: mm,hwpoison: double-check page count in __get_any_page()
has been added to the -mm tree. Its filename is
mmhwpoison-double-check-page-count-in-__get_any_page.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mmhwpoison-double-check-page-count-in-__get_any_page.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mmhwpoison-double-check-page-count-in-__get_any_page.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Subject: mm,hwpoison: double-check page count in __get_any_page()
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.
Link: http://lkml.kernel.org/r/20200806184923.7007-13-nao.horiguchi@xxxxxxxxx
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Reported-by: Qian Cai <cai@xxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Dmitry Yakunin <zeil@xxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/mm/memory-failure.c~mmhwpoison-double-check-page-count-in-__get_any_page
+++ a/mm/memory-failure.c
@@ -1707,6 +1707,9 @@ static int __get_any_page(struct page *p
} 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 *pag
{
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)) {
/*
_
Patches currently in -mm which might be from naoya.horiguchi@xxxxxxx are
mmhwpoison-cleanup-unused-pagehuge-check.patch
mm-hwpoison-remove-recalculating-hpage.patch
mmhwpoison-inject-dont-pin-for-hwpoison_filter.patch
mmhwpoison-introduce-mf_msg_unsplit_thp.patch
mmhwpoison-double-check-page-count-in-__get_any_page.patch
