madvise_free, thp: fix madvise_free_huge_pmd return value after splitting

madvise_free_huge_pmd should return 0 if the fallback PTE operations are
required.  In madvise_free_huge_pmd, if part pages of THP are discarded,
the THP will be split and fallback PTE operations should be used if
splitting succeeds.  But the original code will make fallback PTE
operations skipped, after splitting succeeds.  Fix that via make
madvise_free_huge_pmd return 0 after splitting successfully, so that the
fallback PTE operations will be done.

Link: http://lkml.kernel.org/r/1467135452-16688-1-git-send-email-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9ed58530f6957bef1e2e0fa166ed87085dcae523..55940d17331871b7de478796764d2ef62aef12a4 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1624,14 +1624,9 @@ int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
        if (next - addr != HPAGE_PMD_SIZE) {
                get_page(page);
                spin_unlock(ptl);
-               if (split_huge_page(page)) {
-                       put_page(page);
-                       unlock_page(page);
-                       goto out_unlocked;
-               }
+               split_huge_page(page);
                put_page(page);
                unlock_page(page);
-               ret = 1;
                goto out_unlocked;
        }