mm: fix error case in mlock downgrade reversion

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@safari.iki.fi>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mlock.c b/mm/mlock.c
index 13e0f9af3bd17ac9f8dc5366e96f68c28a88ac12..64dca47c5cbef2558a7db958f4eaa17545eb8d24 100644 (file)
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -310,7 +310,10 @@ long mlock_vma_pages_range(struct vm_area_struct *vma,
                        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;
        }
 
        /*