mm: hugetlb: fix non-atomic enqueue of huge page
Hillf Danton [Wed, 28 Dec 2011 23:57:16 +0000 (15:57 -0800)]
commit b0365c8d0cb6e79eb5f21418ae61ab511f31b575 upstream.

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

Signed-off-by: Hillf Danton <dhillf@gmail.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

mm/hugetlb.c

index 73f17c0..2316840 100644 (file)
@@ -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: