There is an optimization in chmod(1), that makes it not to call chmod(2)

if the new file mode is the same as it was before; however, this
optimization must be disabled for filesystems that support NFSv4 ACLs.
Chmod uses pathconf(2) to determine whether this is the case - however,
pathconf(2) always follows symbolic links, while the 'chmod -h' doesn't.

This change adds lpathconf(3) to make it possible to solve that problem
in a clean way.

Reviewed by:	rwatson (earlier version)
Approved by:	re (kib)

2 files changed, 24 insertions, 4 deletions

diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
index 940f13d..4e2e99c 100644
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -910,5 +910,6 @@
 				    struct msqid_ds *buf); }
 512	AUE_SHMCTL	NOSTD	{ int shmctl(int shmid, int cmd, \
 				    struct shmid_ds *buf); }
+513	AUE_LPATHCONF	STD	{ int lpathconf(char *path, int name); }
 ; Please copy any additions and changes to the following compatability tables:
 ; sys/compat/freebsd32/syscalls.master
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 7252c47..28d95e2e 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -2506,17 +2506,36 @@ pathconf(td, uap)
 	} */ *uap;
 {
 
-	return (kern_pathconf(td, uap->path, UIO_USERSPACE, uap->name));
+	return (kern_pathconf(td, uap->path, UIO_USERSPACE, uap->name, FOLLOW));
+}
+
+#ifndef _SYS_SYSPROTO_H_
+struct lpathconf_args {
+	char	*path;
+	int	name;
+};
+#endif
+int
+lpathconf(td, uap)
+	struct thread *td;
+	register struct lpathconf_args /* {
+		char *path;
+		int name;
+	} */ *uap;
+{
+
+	return (kern_pathconf(td, uap->path, UIO_USERSPACE, uap->name, NOFOLLOW));
 }
 
 int
-kern_pathconf(struct thread *td, char *path, enum uio_seg pathseg, int name)
+kern_pathconf(struct thread *td, char *path, enum uio_seg pathseg, int name,
+    u_long flags)
 {
 	struct nameidata nd;
 	int error, vfslocked;
 
-	NDINIT(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF | MPSAFE |
-	    AUDITVNODE1, pathseg, path, td);
+	NDINIT(&nd, LOOKUP, LOCKSHARED | LOCKLEAF | MPSAFE | AUDITVNODE1 |
+	    flags, pathseg, path, td);
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	vfslocked = NDHASGIANT(&nd);