[patch 41/53] mm: fix error case in mlock downgrade reversion

[Greg KH]

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

From: Hugh Dickins <hugh@xxxxxxxxxxx>

commit d5b562330ec766292a3ac54ae5e0673610bd5b3d upstream.

Commit 27421e211a39784694b597dbf35848b88363c248, Manually revert
"mlock: downgrade mmap sem while populating mlocked regions", has
introduced its own regression: __mlock_vma_pages_range() may report
an error (for example, -EFAULT from trying to lock down pages from
beyond EOF), but mlock_vma_pages_range() must hide that from its
callers as before.

Reported-by: Sami Farin <safari-kernel@xxxxxxxxxxxxx>
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

---
 mm/mlock.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -310,7 +310,10 @@ long mlock_vma_pages_range(struct vm_are
 			is_vm_hugetlb_page(vma) ||
 			vma == get_gate_vma(current))) {
 
-		return __mlock_vma_pages_range(vma, start, end, 1);
+		__mlock_vma_pages_range(vma, start, end, 1);
+
+		/* Hide errors from mmap() and other callers */
+		return 0;
 	}
 
 	/*

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