Re: flock in 2.20.1 can no longer lock the file it will execute

[Karel Zak <kzak@redhat.com>]

On Mon, Nov 14, 2011 at 01:23:38AM -0500, Mike Frysinger wrote:
> i've been using a trick with flock to add locking to all of my shell scripts.  
> basically, i take a lock on the shell script itself:
> 	flock -eon ./test.sh ./test.sh
> 
> with <=util-linux-2.20, this has worked fine.  but starting with 2.20.1, i now 
> get -ETXTBSY (on ext4, but i doubt that matters):
> 	$ echo '#!/bin/sh' > test.sh
> 	$ chmod a+rx test.sh 
> 	$ ./flock -eon ./test.sh ./test.sh 
> 	./flock: ./test.sh: Text file busy
> 
> the only commit made to flock.c between 2.20 and 2.20.1 is this:
> 	commit 75aaee08f06b92d119ed827c53d1af5474eb16ff
> 	flock: make flock(1) work on NFSv4
> 
> and indeed, reverting that made my life happy again.  reading the small patch 
> shows the obvious flaw: you can't open a file for O_RDWR and attempt to execute 
> it at the same time.

 Hmm... maybe we can add a new --read-write command line option for
 NFS guys rather than be smart with access(). The regression is
 unacceptable.

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com