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-rw-r--r--include/linux/poison.h9
-rw-r--r--mm/hugetlb.c5
2 files changed, 13 insertions, 1 deletions
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 2110a81c5e2a..34066ffd893d 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -48,6 +48,15 @@
#define POISON_FREE 0x6b /* for use-after-free poisoning */
#define POISON_END 0xa5 /* end-byte of poisoning */
+/********** mm/hugetlb.c **********/
+/*
+ * Private mappings of hugetlb pages use this poisoned value for
+ * page->mapping. The core VM should not be doing anything with this mapping
+ * but futex requires the existence of some page->mapping value even though it
+ * is unused if PAGE_MAPPING_ANON is set.
+ */
+#define HUGETLB_POISON ((void *)(0x00300300 + POISON_POINTER_DELTA + PAGE_MAPPING_ANON))
+
/********** arch/$ARCH/mm/init.c **********/
#define POISON_FREE_INITMEM 0xcc
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6034dc9e9796..ffbdfc86aedf 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -546,6 +546,7 @@ static void free_huge_page(struct page *page)
mapping = (struct address_space *) page_private(page);
set_page_private(page, 0);
+ page->mapping = NULL;
BUG_ON(page_count(page));
INIT_LIST_HEAD(&page->lru);
@@ -2447,8 +2448,10 @@ retry:
spin_lock(&inode->i_lock);
inode->i_blocks += blocks_per_huge_page(h);
spin_unlock(&inode->i_lock);
- } else
+ } else {
lock_page(page);
+ page->mapping = HUGETLB_POISON;
+ }
}
/*