Make ftruncate a 'struct file' operation rather than a vnode operation.

This makes it possible to support ftruncate() on non-vnode file types in
the future.
- 'struct fileops' grows a 'fo_truncate' method to handle an ftruncate() on
  a given file descriptor.
- ftruncate() moves to kern/sys_generic.c and now just fetches a file
  object and invokes fo_truncate().
- The vnode-specific portions of ftruncate() move to vn_truncate() in
  vfs_vnops.c which implements fo_truncate() for vnode file types.
- Non-vnode file types return EINVAL in their fo_truncate() method.

Submitted by:	rwatson

1 files changed, 14 insertions, 0 deletions

diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
index 27ecf80..457f30b 100644
--- a/sys/kern/sys_pipe.c
+++ b/sys/kern/sys_pipe.c
@@ -140,6 +140,7 @@ __FBSDID("$FreeBSD$");
  */
 static fo_rdwr_t	pipe_read;
 static fo_rdwr_t	pipe_write;
+static fo_truncate_t	pipe_truncate;
 static fo_ioctl_t	pipe_ioctl;
 static fo_poll_t	pipe_poll;
 static fo_kqfilter_t	pipe_kqfilter;
@@ -149,6 +150,7 @@ static fo_close_t	pipe_close;
 static struct fileops pipeops = {
 	.fo_read = pipe_read,
 	.fo_write = pipe_write,
+	.fo_truncate = pipe_truncate,
 	.fo_ioctl = pipe_ioctl,
 	.fo_poll = pipe_poll,
 	.fo_kqfilter = pipe_kqfilter,
@@ -1230,6 +1232,18 @@ pipe_write(fp, uio, active_cred, flags, td)
 	return (error);
 }
 
+/* ARGSUSED */
+static int
+pipe_truncate(fp, length, active_cred, td)
+	struct file *fp;
+	off_t length;
+	struct ucred *active_cred;
+	struct thread *td;
+{
+
+	return (EINVAL);
+}
+
 /*
  * we implement a very minimal set of ioctls for compatibility with sockets.
  */