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, 11 insertions, 0 deletions

diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index b5d01d07621c..171a150d862f 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -105,6 +105,7 @@ static void	kqueue_fo_release(int filt);
 
 static fo_rdwr_t	kqueue_read;
 static fo_rdwr_t	kqueue_write;
+static fo_truncate_t	kqueue_truncate;
 static fo_ioctl_t	kqueue_ioctl;
 static fo_poll_t	kqueue_poll;
 static fo_kqfilter_t	kqueue_kqfilter;
@@ -114,6 +115,7 @@ static fo_close_t	kqueue_close;
 static struct fileops kqueueops = {
 	.fo_read = kqueue_read,
 	.fo_write = kqueue_write,
+	.fo_truncate = kqueue_truncate,
 	.fo_ioctl = kqueue_ioctl,
 	.fo_poll = kqueue_poll,
 	.fo_kqfilter = kqueue_kqfilter,
@@ -1324,6 +1326,15 @@ kqueue_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
 
 /*ARGSUSED*/
 static int
+kqueue_truncate(struct file *fp, off_t length, struct ucred *active_cred,
+	struct thread *td)
+{
+
+	return (EINVAL);
+}
+
+/*ARGSUSED*/
+static int
 kqueue_ioctl(struct file *fp, u_long cmd, void *data,
 	struct ucred *active_cred, struct thread *td)
 {