Subject: + mm-memory-failurec-fix-memory-leak-in-successful-soft-offlining.patch added to -mm tree
To: n-horiguchi@xxxxxxxxxxxxx,andi@xxxxxxxxxxxxxx,mel@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 28 May 2013 13:34:12 -0700
The patch titled
Subject: mm/memory-failure.c: fix memory leak in successful soft offlining
has been added to the -mm tree. Its filename is
mm-memory-failurec-fix-memory-leak-in-successful-soft-offlining.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/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: mm/memory-failure.c: fix memory leak in successful soft offlining
After a successful page migration by soft offlining, the source page is
not properly freed and it's never reusable even if we unpoison it
afterward.
This is caused by the race between freeing page and setting PG_hwpoison.
In successful soft offlining, the source page is put (and the refcount
becomes 0) by putback_lru_page() in unmap_and_move(), where it's linked to
pagevec and actual freeing back to buddy is delayed. So if PG_hwpoison is
set for the page before freeing, the freeing does not functions as
expected (in such case freeing aborts in free_pages_prepare() check.)
This patch tries to make sure to free the source page before setting
PG_hwpoison on it. To avoid reallocating, the page keeps MIGRATE_ISOLATE
until after setting PG_hwpoison.
This patch also removes obsolete comments about "keeping elevated
refcount" because what they say is not true. Unlike memory_failure(),
soft_offline_page() uses no special page isolation code, and the
soft-offlined pages have no elevated.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)
diff -puN mm/memory-failure.c~mm-memory-failurec-fix-memory-leak-in-successful-soft-offlining mm/memory-failure.c
--- a/mm/memory-failure.c~mm-memory-failurec-fix-memory-leak-in-successful-soft-offlining
+++ a/mm/memory-failure.c
@@ -1410,7 +1410,8 @@ static int __get_any_page(struct page *p
/*
* Isolate the page, so that it doesn't get reallocated if it
- * was free.
+ * was free. This flag should be kept set until the source page
+ * is freed and PG_hwpoison on it is set.
*/
set_migratetype_isolate(p, true);
/*
@@ -1433,7 +1434,6 @@ static int __get_any_page(struct page *p
/* Not a free page */
ret = 1;
}
- unset_migratetype_isolate(p, MIGRATE_MOVABLE);
unlock_memory_hotplug();
return ret;
}
@@ -1494,7 +1494,6 @@ static int soft_offline_huge_page(struct
atomic_long_add(1 << compound_trans_order(hpage),
&num_poisoned_pages);
}
- /* keep elevated page count for bad page */
return ret;
}
@@ -1559,7 +1558,7 @@ int soft_offline_page(struct page *page,
atomic_long_inc(&num_poisoned_pages);
}
}
- /* keep elevated page count for bad page */
+ unset_migratetype_isolate(page, MIGRATE_MOVABLE);
return ret;
}
@@ -1625,7 +1624,22 @@ static int __soft_offline_page(struct pa
if (ret > 0)
ret = -EIO;
} else {
+ /*
+ * After page migration succeeds, the source page can
+ * be trapped in pagevec and actual freeing is delayed.
+ * Freeing code works differently based on PG_hwpoison,
+ * so there's a race. We need to make sure that the
+ * source page should be freed back to buddy before
+ * setting PG_hwpoison.
+ */
+ if (!is_free_buddy_page(page))
+ lru_add_drain_all();
+ if (!is_free_buddy_page(page))
+ drain_all_pages();
SetPageHWPoison(page);
+ if (!is_free_buddy_page(page))
+ pr_info("soft offline: %#lx: page leaked\n",
+ pfn);
atomic_long_inc(&num_poisoned_pages);
}
} else {
_
Patches currently in -mm which might be from n-horiguchi@xxxxxxxxxxxxx are
mm-memory-failurec-fix-memory-leak-in-successful-soft-offlining.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
