Re: [PATCH 2/2] nfsd: only set file_lock.fl_lmops in nfsd4_lockt if a stateowner is found

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Jan 21, 2009 at 11:34:51AM -0500, Jeff Layton wrote:
> nfsd4_lockt does a search for a lockstateowner when building the lock
> struct to test. If one is found, it'll set fl_owner to it. Regardless of
> whether that happens, it'll also set fl_lmops.
> 
> If a lockstateowner is not found, then we'll have fl_owner set to NULL
> and fl_lmops set pointing to nfsd_posix_mng_ops. Other parts of the
> NFSv4 server code assume that fl_owner will point to a valid
> nfs4_stateowner if fl_lmops is set this way.
> 
> This behavior exposed a bug in DLM's GETLK implementation where it
> wasn't clearing out the fields in the file_lock before filling in
> conflicting lock info. While we were able to fix this in DLM, it
> still seems pointless and dangerous to set the fl_lmops this way
> when we have a NULL lockstateowner.
> 
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> ---
>  fs/nfsd/nfs4state.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 88db7d3..07d196a 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -2867,11 +2867,13 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  
>  	lockt->lt_stateowner = find_lockstateowner_str(inode,
>  			&lockt->lt_clientid, &lockt->lt_owner);
> -	if (lockt->lt_stateowner)
> +	if (lockt->lt_stateowner) {
>  		file_lock.fl_owner = (fl_owner_t)lockt->lt_stateowner;
> +		file_lock.fl_lmops = &nfsd_posix_mng_ops;

So I think we just shouldn't need this second assignment at all.

--b.

> +	}
> +
>  	file_lock.fl_pid = current->tgid;
>  	file_lock.fl_flags = FL_POSIX;
> -	file_lock.fl_lmops = &nfsd_posix_mng_ops;
>  
>  	file_lock.fl_start = lockt->lt_offset;
>  	file_lock.fl_end = last_byte_offset(lockt->lt_offset, lockt->lt_length);
> -- 
> 1.5.5.6
> 
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