CRED: Wrap task credential accesses in the JFS filesystem

Wrap access to task credentials so that they can be separated more easily from
the task_struct during the introduction of COW creds.

Change most current->(|e|s|fs)[ug]id to current_(|e|s|fs)[ug]id().

Change some task->e?[ug]id to task_e?[ug]id().  In some places it makes more
sense to use RCU directly rather than a convenient wrapper; these will be
addressed by later patches.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Dave Kleikamp <shaggy@austin.ibm.com>
Cc: jfs-discussion@lists.sourceforge.net
Signed-off-by: James Morris <jmorris@namei.org>

fs/jfs/jfs_inode.c

@@ -93,13 +93,13 @@ struct inode *ialloc(struct inode *parent, umode_t mode)
 		return ERR_PTR(rc);
 	}
 
-	inode->i_uid = current->fsuid;
+	inode->i_uid = current_fsuid();
 	if (parent->i_mode & S_ISGID) {
 		inode->i_gid = parent->i_gid;
 		if (S_ISDIR(mode))
 			mode |= S_ISGID;
 	} else
-		inode->i_gid = current->fsgid;
+		inode->i_gid = current_fsgid();
 
 	/*
 	 * New inodes need to save sane values on disk when