[PATCH] mm: hugetlb: fix non-atomic enqueue of huge page

[Hillf Danton <dhillf@gmail.com>]

From: Hillf Danton <dhillf@gmail.com>
Subject: [PATCH] mm: hugetlb: fix non-atomic enqueue of huge page

If huge page is enqueued under the protection of hugetlb_lock, then
the operation is atomic and safe.

Cc: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Hillf Danton <dhillf@gmail.com>
---

--- a/mm/hugetlb.c	Tue Dec 20 21:26:30 2011
+++ b/mm/hugetlb.c	Fri Dec 23 21:16:28 2011
@@ -901,7 +901,6 @@ retry:
 	h->resv_huge_pages += delta;
 	ret = 0;

-	spin_unlock(&hugetlb_lock);
 	/* Free the needed pages to the hugetlb pool */
 	list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
 		if ((--needed) < 0)
@@ -915,6 +914,7 @@ retry:
 		VM_BUG_ON(page_count(page));
 		enqueue_huge_page(h, page);
 	}
+	spin_unlock(&hugetlb_lock);

 	/* Free unnecessary surplus pages to the buddy allocator */
 free:

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