/proc/pid/pagemap: document in Documentation/filesystems/proc.txt

Document /proc/pid/pagemap in Documentation/filesystems/proc.txt
Signed-off-by: NNikanth Karthikesan <knikanth@suse.de>
Cc: Richard Guenther <rguenther@suse.de>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: NMatt 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

@@ -136,6 +136,7 @@ Table 1-1: Process specific entries in /proc
  statm		Process memory status information
  status		Process status in human readable form
  wchan		If CONFIG_KALLSYMS is set, a pre-decoded wchan
+ pagemap	Page table
  stack		Report full stack trace, enable via CONFIG_STACKTRACE
  smaps		a extension based on maps, showing the memory consumption of
 		each mapping
@@ -404,6 +405,9 @@ To clear the bits for the file mapped pages associated with the process
     > echo 3 > /proc/PID/clear_refs
 Any other value written to /proc/PID/clear_refs will have no effect.
 
+The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
+using /proc/kpageflags and number of times a page is mapped using
+/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
 
 1.2 Kernel data
 ---------------