mm: smaps: export mlock information

Currently there is no way to find whether a process has locked its pages
in memory or not.  And which of the memory regions are locked in memory.

Add a new field "Locked" to export this information via the smaps file.
Signed-off-by: NNikanth Karthikesan <knikanth@suse.de>
Acked-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: NWu Fengguang <fengguang.wu@intel.com>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Documentation/filesystems/proc.txt

@@ -375,6 +375,7 @@ Anonymous:             0 kB
 Swap:                  0 kB
 KernelPageSize:        4 kB
 MMUPageSize:           4 kB
+Locked:              374 kB
 
 The first of these lines shows the same information as is displayed for the
 mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
@@ -670,6 +671,8 @@ varies by architecture and compile options.  The following is from a
 
 > cat /proc/meminfo
 
+The "Locked" indicates whether the mapping is locked in memory or not.
+
 
 MemTotal:     16344972 kB
 MemFree:      13634064 kB

fs/proc/task_mmu.c

@@ -418,7 +418,8 @@ static int show_smap(struct seq_file *m, void *v)
 		   "Anonymous:      %8lu kB\n"
 		   "Swap:           %8lu kB\n"
 		   "KernelPageSize: %8lu kB\n"
-		   "MMUPageSize:    %8lu kB\n",
+		   "MMUPageSize:    %8lu kB\n"
+		   "Locked:         %8lu kB\n",
 		   (vma->vm_end - vma->vm_start) >> 10,
 		   mss.resident >> 10,
 		   (unsigned long)(mss.pss >> (10 + PSS_SHIFT)),
@@ -430,7 +431,9 @@ static int show_smap(struct seq_file *m, void *v)
 		   mss.anonymous >> 10,
 		   mss.swap >> 10,
 		   vma_kernel_pagesize(vma) >> 10,
-		   vma_mmu_pagesize(vma) >> 10);
+		   vma_mmu_pagesize(vma) >> 10,
+		   (vma->vm_flags & VM_LOCKED) ?
+			(unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);
 
 	if (m->count < m->size)  /* vma is copied successfully */
 		m->version = (vma != get_gate_vma(task)) ? vma->vm_start : 0;