diff mbox series

[054/156] mm,hwpoison: try to narrow window race for free pages

Message ID 20201016024416.RNt5orXte%akpm@linux-foundation.org
State New
Headers show
Series [001/156] device-dax/kmem: fix resource release | expand

Commit Message

Andrew Morton Oct. 16, 2020, 2:44 a.m. UTC
From: Oscar Salvador <osalvador@suse.de>
Subject: mm,hwpoison: try to narrow window race for free pages

Aristeu Rozanski reported that a customer test case started to report
-EBUSY after the hwpoison rework patchset.

There is a race window between spotting a free page and taking it off its
buddy freelist, so it might be that by the time we try to take it off, the
page has been already allocated.

This patch tries to handle such race window by trying to handle the new
type of page again if the page was allocated under us.

Link: https://lkml.kernel.org/r/20200922135650.1634-15-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reported-by: Aristeu Rozanski <aris@ruivo.org>
Tested-by: Aristeu Rozanski <aris@ruivo.org>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dmitry Yakunin <zeil@yandex-team.ru>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory-failure.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
diff mbox series

Patch

--- a/mm/memory-failure.c~mmhwpoison-try-to-narrow-window-race-for-free-pages
+++ a/mm/memory-failure.c
@@ -1903,6 +1903,7 @@  int soft_offline_page(unsigned long pfn,
 {
 	int ret;
 	struct page *page;
+	bool try_again = true;
 
 	if (!pfn_valid(pfn))
 		return -ENXIO;
@@ -1918,6 +1919,7 @@  int soft_offline_page(unsigned long pfn,
 		return 0;
 	}
 
+retry:
 	get_online_mems();
 	ret = get_any_page(page, pfn, flags);
 	put_online_mems();
@@ -1925,7 +1927,10 @@  int soft_offline_page(unsigned long pfn,
 	if (ret > 0)
 		ret = soft_offline_in_use_page(page);
 	else if (ret == 0)
-		ret = soft_offline_free_page(page);
+		if (soft_offline_free_page(page) && try_again) {
+			try_again = false;
+			goto retry;
+		}
 
 	return ret;
 }