CRED: Wrap task credential accesses in the BFS 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>
Cc: Tigran A. Aivazian <tigran@aivazian.fsnet.co.uk>
Signed-off-by: James Morris <jmorris@namei.org>

fs/bfs/dir.c

@@ -106,8 +106,8 @@ static int bfs_create(struct inode *dir, struct dentry *dentry, int mode,
 	}
 	set_bit(ino, info->si_imap);
 	info->si_freei--;
-	inode->i_uid = current->fsuid;
-	inode->i_gid = (dir->i_mode & S_ISGID) ? dir->i_gid : current->fsgid;
+	inode->i_uid = current_fsuid();
+	inode->i_gid = (dir->i_mode & S_ISGID) ? dir->i_gid : current_fsgid();
 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
 	inode->i_blocks = 0;
 	inode->i_op = &bfs_file_inops;