fs/proc/task_mmu.c: fix Locked field in /proc/pid/smaps*

Thomas reports:

: While looking around in /proc on my v4.14.52 system I noticed that
: all processes got a lot of "Locked" memory in /proc/*/smaps. A lot
: more memory than a regular user can usually lock with mlock().
:
: commit 493b0e9d945fa9dfe96be93ae41b4ca4b6fdb317 (v4.14-rc1) seems
: to have changed the behavior of "Locked".
:
: Before that commit the code was like this. Notice the VM_LOCKED
: check.
:
:          (vma->vm_flags & VM_LOCKED) ?
:               (unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);
:
: After that commit Locked is now the same as Pss. This looks like a
: mistake.
:
: (unsigned long)(mss->pss >> (10 + PSS_SHIFT)));

Indeed, the commit has added mss->pss_locked with the correct value that
depends on VM_LOCKED, but forgot to actually use it. Fix it.

Link: http://lkml.kernel.org/r/ebf6c7fb-fec3-6a26-544f-710ed193c154@suse.cz
Fixes: 493b0e9d945f ("mm: add /proc/pid/smaps_rollup")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Thomas Lindroth <thomas.lindroth@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e967901..dfd73a4 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -831,7 +831,8 @@
 		SEQ_PUT_DEC(" kB\nSwap:           ", mss->swap);
 		SEQ_PUT_DEC(" kB\nSwapPss:        ",
 						mss->swap_pss >> PSS_SHIFT);
-		SEQ_PUT_DEC(" kB\nLocked:         ", mss->pss >> PSS_SHIFT);
+		SEQ_PUT_DEC(" kB\nLocked:         ",
+						mss->pss_locked >> PSS_SHIFT);
 		seq_puts(m, " kB\n");
 	}
 	if (!rollup_mode) {