new helper: fixed_size_llseek()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1db01c1..803b7fa 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2428,6 +2428,8 @@
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence);
 extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
 		int whence, loff_t maxsize, loff_t eof);
+extern loff_t fixed_size_llseek(struct file *file, loff_t offset,
+		int whence, loff_t size);
 extern int generic_file_open(struct inode * inode, struct file * filp);
 extern int nonseekable_open(struct inode * inode, struct file * filp);