[patch 15/18] Ignore madvise(MADV_WILLNEED) for hugetlbfs-backed regions

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Mel Gorman <mel@xxxxxxxxx>

commit a425a638c858fd10370b573bde81df3ba500e271 upstream.

madvise(MADV_WILLNEED) forces page cache readahead on a range of memory
backed by a file.  The assumption is made that the page required is
order-0 and "normal" page cache.

On hugetlbfs, this assumption is not true and order-0 pages are
allocated and inserted into the hugetlbfs page cache.  This leaks
hugetlbfs page reservations and can cause BUGs to trigger related to
corrupted page tables.

This patch causes MADV_WILLNEED to be ignored for hugetlbfs-backed
regions.

Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
Cc: stable@xxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 mm/madvise.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -112,6 +112,14 @@ static long madvise_willneed(struct vm_a
 	if (!file)
 		return -EBADF;
 
+	/*
+	 * Page cache readahead assumes page cache pages are order-0 which
+	 * is not the case for hugetlbfs. Do not give a bad return value
+	 * but ignore the advice.
+	 */
+	if (vma->vm_flags & VM_HUGETLB)
+		return 0;
+
 	if (file->f_mapping->a_ops->get_xip_mem) {
 		/* no bad return value, but ignore advice */
 		return 0;


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