kern/68459: Patches to mknod(2) behave more like Linux

[Joao Carlos Mendes Luis]

>Number:         68459
>Category:       kern
>Synopsis:       Patches to mknod(2) behave more like Linux
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jun 28 23:00:30 GMT 2004
>Closed-Date:
>Last-Modified:
>Originator:     Joao Carlos Mendes Luis
>Release:        FreeBSD 4.10-BETA i386
>Organization:
Barradev Tecnologia Ltda.
>Environment:
System: FreeBSD roma.coe.ufrj.br 4.10-BETA FreeBSD 4.10-BETA #4: Fri Apr 16 03:25:06 BRT 2004 jonny at roma.coe.ufrj.br:/usr/cvsup/RELENG_4/src/sys/compile/ROMA i386


FreeBSD 4-stable VFS subsystem

>Description:

Here a copy of an email sent to -hackers:

    I´ve done some changes to the kernel mknod(2) handling to make it more compatible to the Linux behaviour, allowing one to create files of type VREG, VSOCK and VFIFO with mknod(2).  I already know that BSD way is that one should use creat(2), bind(2) and mkfifo(2) functions for these, but, if all these are indeed vnodes, why bother if one use mkfifo(2) or mknod(2) to create fifos?? The only vnode type I think I left out is VDIR, because it needs to be initialized with "." and "..".

    I first came with this idea using rsync for a full backup, noticing it could not copy fifos or sockets.  I could simply fix rsync, but I thought "fixing" FreeBSD would be a little bit funnier!  

    To allow your appreciation, here are my patches.  I am not an expert in VFS coding, so it should probably be checked by an expert before commiting.  All I can say is that it worked for me.

>How-To-Repeat:

Here's a small test program:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

main()
{
  mknod( "test1", S_IFSOCK|0777, 0 );
  perror( "mknod" );
  errno=0;
  mknod( "test2", S_IFIFO|0777, 0 );
  perror( "mknod" );
  errno=0;
  mknod( "test3", S_IFREG|0777, 0 );
  perror( "mknod" );
  errno=0;
  mknod( "test4", S_IFBLK|0777, 0 );
  perror( "mknod" );
  errno=0;
  mknod( "test5", S_IFCHR|0777, 0 );
  perror( "mknod" );
  errno=0;
}

>Fix:

The following patches should be verified by a VFS expert.

A merge to -current should follow, of course.

--- RELENG_4/src/sys/kern/vfs_syscalls.c.orig	Mon Jun 28 18:11:58 2004
+++ RELENG_4/src/sys/kern/vfs_syscalls.c	Mon Jun 28 19:26:31 2004
@@ -1187,14 +1187,20 @@
 	register struct vnode *vp;
 	struct vattr vattr;
 	int error;
-	int whiteout = 0;
+	int vtype;
 	struct nameidata nd;
 
-	switch (SCARG(uap, mode) & S_IFMT) {
+	vtype = SCARG(uap, mode) & S_IFMT;
+	switch ( vtype ) {
 	case S_IFCHR:
 	case S_IFBLK:
 		error = suser(p);
 		break;
+	case S_IFREG:
+	case S_IFIFO:
+	case S_IFSOCK:
+		error = 0;
+		break;
 	default:
 		error = suser_xxx(0, p, PRISON_ROOT);
 		break;
@@ -1202,7 +1208,7 @@
 	if (error)
 		return (error);
 	bwillwrite();
-	NDINIT(&nd, CREATE, LOCKPARENT, UIO_USERSPACE, SCARG(uap, path), p);
+	NDINIT(&nd, CREATE, LOCKPARENT, (vtype==S_IFSOCK)?UIO_SYSSPACE:UIO_USERSPACE, SCARG(uap, path), p);
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	vp = nd.ni_vp;
@@ -1212,9 +1218,8 @@
 		VATTR_NULL(&vattr);
 		vattr.va_mode = (SCARG(uap, mode) & ALLPERMS) &~ p->p_fd->fd_cmask;
 		vattr.va_rdev = SCARG(uap, dev);
-		whiteout = 0;
 
-		switch (SCARG(uap, mode) & S_IFMT) {
+		switch ( vtype ) {
 		case S_IFMT:	/* used by badsect to flag bad sectors */
 			vattr.va_type = VBAD;
 			break;
@@ -1224,8 +1229,17 @@
 		case S_IFBLK:
 			vattr.va_type = VBLK;
 			break;
+		case S_IFREG:
+			vattr.va_type = VREG;
+			break;
+		case S_IFSOCK:
+			vattr.va_type = VSOCK;
+			break;
+		case S_IFIFO:
+			vattr.va_type = VFIFO;
+			break;
 		case S_IFWHT:
-			whiteout = 1;
+			/* NOTHING */
 			break;
 		default:
 			error = EINVAL;
@@ -1234,9 +1248,18 @@
 	}
 	if (!error) {
 		VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
-		if (whiteout)
+		switch ( vtype ) {
+		    case S_IFWHT:
 			error = VOP_WHITEOUT(nd.ni_dvp, &nd.ni_cnd, CREATE);
-		else {
+			break;
+		    case S_IFREG:
+		    case S_IFSOCK:
+			error = VOP_CREATE(nd.ni_dvp, &nd.ni_vp,
+						&nd.ni_cnd, &vattr);
+			if (error == 0)
+				vput(nd.ni_vp);
+		        break;
+		    default:
 			error = VOP_MKNOD(nd.ni_dvp, &nd.ni_vp,
 						&nd.ni_cnd, &vattr);
 			if (error == 0)


>Release-Note:
>Audit-Trail:
>Unformatted: