- Implement a lockless file descriptor lookup algorithm in

   fget_unlocked().
 - Save old file descriptor tables created on expansion until
   the entire descriptor table is freed so that pointers may be
   followed without regard for expanders.
 - Mark the file zone as NOFREE so we may attempt to reference
   potentially freed files.
 - Convert several fget_locked() users to fget_unlocked().  This
   requires us to manage reference counts explicitly but reduces
   locking overhead in the common case.

1 files changed, 5 insertions, 14 deletions

diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 64ca316..ae3904d 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -4235,22 +4235,13 @@ getvnode(fdp, fd, fpp)
 	int error;
 	struct file *fp;
 
+	error = 0;
 	fp = NULL;
-	if (fdp == NULL)
+	if (fdp == NULL || (fp = fget_unlocked(fdp, fd)) == NULL)
 		error = EBADF;
-	else {
-		FILEDESC_SLOCK(fdp);
-		if ((u_int)fd >= fdp->fd_nfiles ||
-		    (fp = fdp->fd_ofiles[fd]) == NULL)
-			error = EBADF;
-		else if (fp->f_vnode == NULL) {
-			fp = NULL;
-			error = EINVAL;
-		} else {
-			fhold(fp);
-			error = 0;
-		}
-		FILEDESC_SUNLOCK(fdp);
+	else if (fp->f_vnode == NULL) {
+		error = EINVAL;
+		fdrop(fp, curthread);
 	}
 	*fpp = fp;
 	return (error);