+ mmhwpoison-drain-pcplists-before-bailing-out-for-non-buddy-zero-refcount-page.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm,hwpoison: drain pcplists before bailing out for non-buddy zero-refcount page
has been added to the -mm tree.  Its filename is
     mmhwpoison-drain-pcplists-before-bailing-out-for-non-buddy-zero-refcount-page.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mmhwpoison-drain-pcplists-before-bailing-out-for-non-buddy-zero-refcount-page.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mmhwpoison-drain-pcplists-before-bailing-out-for-non-buddy-zero-refcount-page.patch

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------------------------------------------------------
From: Oscar Salvador <osalvador@suse.de>
Subject: mm,hwpoison: drain pcplists before bailing out for non-buddy zero-refcount page

A page with 0-refcount and !PageBuddy could perfectly be a pcppage. 
Currently, we bail out with an error if we encounter such a page, meaning
that we do not handle pcppages neither from hard-offline nor from
soft-offline path.

Fix this by draining pcplists whenever we find this kind of page and retry
the check again.  It might be that pcplists have been spilled into the
buddy allocator and so we can handle it.

Link: https://lkml.kernel.org/r/20200902094510.10727-4-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory-failure.c |   24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

--- a/mm/memory-failure.c~mmhwpoison-drain-pcplists-before-bailing-out-for-non-buddy-zero-refcount-page
+++ a/mm/memory-failure.c
@@ -950,13 +950,13 @@ static int page_action(struct page_state
 }
 
 /**
- * get_hwpoison_page() - Get refcount for memory error handling:
+ * __get_hwpoison_page() - Get refcount for memory error handling:
  * @page:	raw error page (hit by memory error)
  *
  * Return: return 0 if failed to grab the refcount, otherwise true (some
  * non-zero value.)
  */
-static int get_hwpoison_page(struct page *page)
+static int __get_hwpoison_page(struct page *page)
 {
 	struct page *head = compound_head(page);
 
@@ -986,6 +986,26 @@ static int get_hwpoison_page(struct page
 	return 0;
 }
 
+static int get_hwpoison_page(struct page *p)
+{
+	int ret;
+	bool drained = false;
+
+retry:
+	ret = __get_hwpoison_page(p);
+	if (!ret && !is_free_buddy_page(p) && !page_count(p) && !drained) {
+		/*
+		 * The page might be in a pcplist, so try to drain those
+		 * and see if we are lucky.
+		 */
+		drain_all_pages(page_zone(p));
+		drained = true;
+		goto retry;
+	}
+
+	return ret;
+}
+
 /*
  * Do all that is necessary to remove user space mappings. Unmap
  * the pages and send SIGBUS to the processes if the data was dirty.
_

Patches currently in -mm which might be from osalvador@suse.de are

mmhwpoison-un-export-get_hwpoison_page-and-make-it-static.patch
mmhwpoison-kill-put_hwpoison_page.patch
mmhwpoison-unify-thp-handling-for-hard-and-soft-offline.patch
mmhwpoison-rework-soft-offline-for-free-pages.patch
mmhwpoison-rework-soft-offline-for-in-use-pages.patch
mmhwpoison-refactor-soft_offline_huge_page-and-__soft_offline_page.patch
mmhwpoison-return-0-if-the-page-is-already-poisoned-in-soft-offline.patch
mmhwpoison-take-free-pages-off-the-buddy-freelists.patch
mmhwpoison-refactor-madvise_inject_error.patch
mmhwpoison-drain-pcplists-before-bailing-out-for-non-buddy-zero-refcount-page.patch
mmhwpoison-drop-unneeded-pcplist-draining.patch