[Linux-cluster] Types of file locking support in GFS

[gordan at bobich.net]

What even remotely similar alternatives to GFS are there, though?

On Wed, 12 Dec 2007, Matthew B. Brookover wrote:

> Test carefully, and look at your code.  If your program needs to promote
> a shared lock to an exclusive lock, GFS will allow another program to
> steal the lock.  flock frees the program's shared lock and then tries to
> get an exclusive lock, another thread can sneak in and get a lock.  This
> can cause data corruption if your program expects flock to promote or
> demote a lock without allowing another process to modify the file.
>
> This is not a problem on EXT3.  EXT3 will allow a lock to be promoted
> from shared to exclusive and not allow a second program to sneak in.
>
> See https://bugzilla.redhat.com/show_bug.cgi?id=252000 for more details.
>
> Red Hat said that I should modify my code to use fcntl.  Unfortunately,
> we may end up dropping GFS, and the cluster suite instead.
>
> Matt
>
>
> On Sat, 2007-12-08 at 10:09 +0000, Elliot Moore wrote:
>
>> On 6 Dec 2007, at 13:45, Elliot Moore wrote:
>>> Hi,
>>>
>>> I'm trying to setup activemq with master and slave.
>>> According to http://activemq.apache.org/shared-file-system-master-slave.html
>>> , you can use a SAN to hold a lockfile for multiple brokers to watch.
>>> But the SAN filesystem must support exclusive file locks.
>>>
>>> OCFS2 only supports locking with 'fcntl' and not 'lockf and flock',
>>> therefore mutex file locking from Java isn't supported. (both
>>> brokers think they have
>>> an exclusive lock on the lockfile!)
>>>
>>> Does Redhat GFS support 'lockf and flock' as well as fcntl ?
>>
>>
>> FYI
>> got a response from redhat, yes
>> more information @ http://sources.redhat.com/cluster/faq.html#gfs_vs_ocfs2
>>
>>
>>
>>
>> --
>> Linux-cluster mailing list
>> Linux-cluster at redhat.com
>> https://www.redhat.com/mailman/listinfo/linux-cluster
>