Replace pid_t in autofs with struct pid reference

Make autofs container-friendly by caching struct pid reference rather than
pid_t and using pid_nr() to retreive a task's pid_t.

ChangeLog:
	- Fix Eric Biederman's comments - Use find_get_pid() to hold a
	  reference to oz_pgrp and release while unmounting; separate out
	  changes to autofs and autofs4.
	- Fix Cedric's comments: retain old prototype of parse_options()
	  and move necessary change to its caller.

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: containers@lists.osdl.org
Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/autofs/autofs_i.h b/fs/autofs/autofs_i.h
index 4ef5444..8b4cca3 100644
--- a/fs/autofs/autofs_i.h
+++ b/fs/autofs/autofs_i.h
@@ -101,7 +101,7 @@
 struct autofs_sb_info {
 	u32 magic;
 	struct file *pipe;
-	pid_t oz_pgrp;
+	struct pid *oz_pgrp;
 	int catatonic;
 	struct super_block *sb;
 	unsigned long exp_timeout;
@@ -122,7 +122,7 @@
    filesystem without "magic".) */
 
 static inline int autofs_oz_mode(struct autofs_sb_info *sbi) {
-	return sbi->catatonic || process_group(current) == sbi->oz_pgrp;
+	return sbi->catatonic || task_pgrp(current) == sbi->oz_pgrp;
 }
 
 /* Hash operations */