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From: Ivan Voras <ivoras@freebsd.org>
Subject: lockf(1) and NFS
Date: Fri, 29 Aug 2014 15:04:22 +0200
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Hi,

I had some fun troubleshooting NFS locking and among other things, found
that lockf(1) doesn't really work on NFSv4 mounts. Googling around (so
correct me if I'm wrong), it looks like this is because NFS quietly
translates the old-style locks into POSIX range locks, and those cannot
be acquired exclusively if the file is opened read-only.

I've tested the following patch and it works.
Any objections to committing it?

--- a/lockf.c	Fri Aug 29 14:58:10 2014 +0200
+++ b/lockf.c	Fri Aug 29 14:59:12 2014 +0200
@@ -169,7 +169,7 @@
 {
 	int fd;

-	if ((fd =3D open(name, flags|O_RDONLY|O_EXLOCK|flags, 0666)) =3D=3D -1)=
 {
+	if ((fd =3D open(name, flags|O_RDWR|O_EXLOCK|flags, 0666)) =3D=3D -1) {=

 		if (errno =3D=3D EAGAIN || errno =3D=3D EINTR)
 			return (-1);
 		err(EX_CANTCREAT, "cannot open %s", name);


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