vfs: make no_llseek the default

All file operations now have an explicit .llseek
operation pointer, so we can change the default
action for future code.

This makes changes the default from default_llseek
to no_llseek, which always returns -ESPIPE if
a user tries to seek on a file without a .llseek
operation.

The name of the default_llseek function remains
unchanged, if anyone thinks we should change it,
please speak up.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org

fs/read_write.c

@@ -156,7 +156,6 @@ loff_t vfs_llseek(struct file *file, loff_t offset, int origin)
 
 	fn = no_llseek;
 	if (file->f_mode & FMODE_LSEEK) {
-		fn = default_llseek;
 		if (file->f_op && file->f_op->llseek)
 			fn = file->f_op->llseek;
 	}