[Cluster-devel] Re: [NFS] [PATCH 1/4 Revised] NLM failover - nlm_unlock

[Wendy Cheng <wcheng@redhat.com>]

Neil Brown wrote:
> On Thursday September 14, wcheng at redhat.com wrote:
>   
>> By writing exported filesytem id into /proc/fs/nfsd/nlm_unlock, this 
>> patch walks thru lockd's global nlm_files list to release all the locks 
>> associated with the particular id. It is used to enable NFS lock 
>> failover with active-active clustered servers.
>>
>> Relevant steps:
>> 1) Exports filesystem with "fsid" option as:
>>    /etc/exports entry> /mnt/ext3/exports *(fsid=1234,sync,rw)
>> 2) Drops locks based on fsid by:
>>    shell> echo 1234 > /proc/fs/nfsd/nlm_unlock
>>     
>
> I actually felt a bit more comfortable with the server-ip based
> approach, how I cannot really fault the fsid based approach, and it
> does seem to have some advantages, so I guess we go with it.
>   
Neil,

I replaced the checking inside nlm_traverse_files with nlm_file_inuse() 
as we discussed in:
http://sourceforge.net/mailarchive/forum.php?thread_id=31885384&forum_id=4930

If a separate patch is a better idea, feel free to yank it out. The code 
is based on 2.6.21.rc4 kernel and can be used independently (without 
other NLM failover patches). We submit it earlier (others still being 
worked on) to avoid the tedious rebase efforts. There are also  customer 
requests from our distribution to ask for this function in a single 
server (no cluster) environment.

-- Wendy

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