mm: thp: fix up pmd_trans_unstable() locations

pmd_trans_unstable() should be called before pmd_offset_map() in the
locations where the mmap_sem is held for reading.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mark Salter <msalter@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 9694cc283511..c283832d411d 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -781,9 +781,6 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
         int err = 0;
         pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);
 
-        if (pmd_trans_unstable(pmd))
-                return 0;
-
         /* find the first VMA at or above 'addr' */
         vma = find_vma(walk->mm, addr);
         spin_lock(&walk->mm->page_table_lock);
@@ -802,6 +799,8 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
                 return err;
         }
 
+        if (pmd_trans_unstable(pmd))
+                return 0;
         for (; addr != end; addr += PAGE_SIZE) {
 
                 /* check to see if we've left 'vma' behind