Re: [PATCH v2 1/2] NFSD: handle GETATTR conflict with write delegation

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2023-05-30 at 15:04 -0700, dai.ngo@oracle.com wrote:
> On 5/30/23 3:29 AM, Jeff Layton wrote:
> > On Mon, 2023-05-29 at 23:52 -0700, Dai Ngo wrote:
> > > If the GETATTR request on a file that has write delegation in effect
> > > and the request attributes include the change info and size attribute
> > > then the write delegation is recalled. If the delegation is returned
> > > within 30ms then the GETATTR is serviced as normal otherwise the
> > > NFS4ERR_DELAY error is returned for the GETATTR.
> > > 
> > > Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> > > ---
> > >   fs/nfsd/nfs4state.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> > >   fs/nfsd/nfs4xdr.c   |  5 +++++
> > >   fs/nfsd/state.h     |  3 +++
> > >   3 files changed, 58 insertions(+)
> > > 
> > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > > index b90b74a5e66e..7826483e8421 100644
> > > --- a/fs/nfsd/nfs4state.c
> > > +++ b/fs/nfsd/nfs4state.c
> > > @@ -8353,3 +8353,53 @@ nfsd4_get_writestateid(struct nfsd4_compound_state *cstate,
> > >   {
> > >   	get_stateid(cstate, &u->write.wr_stateid);
> > >   }
> > > +
> > > +/**
> > > + * nfsd4_deleg_getattr_conflict - Trigger recall if GETATTR causes conflict
> > > + * @rqstp: RPC transaction context
> > > + * @inode: file to be checked for a conflict
> > > + *
> > > + * This function is called when there is a conflict between a write
> > > + * delegation and a change/size GETATR from another client. The server
> > > + * must either use the CB_GETATTR to get the current values of the
> > > + * attributes from the client that hold the delegation or recall the
> > > + * delegation before replying to the GETATTR. See RFC 8881 section
> > > + * 18.7.4.
> > > + *
> > > + * Returns 0 if there is no conflict; otherwise an nfs_stat
> > > + * code is returned.
> > > + */
> > > +__be32
> > > +nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct inode *inode)
> > > +{
> > > +	__be32 status;
> > > +	struct file_lock_context *ctx;
> > > +	struct file_lock *fl;
> > > +	struct nfs4_delegation *dp;
> > > +
> > > +	ctx = locks_inode_context(inode);
> > > +	if (!ctx)
> > > +		return 0;
> > > +	spin_lock(&ctx->flc_lock);
> > > +	list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
> > > +		if (fl->fl_flags == FL_LAYOUT ||
> > > +				fl->fl_lmops != &nfsd_lease_mng_ops)
> > > +			continue;
> > > +		if (fl->fl_type == F_WRLCK) {
> > > +			dp = fl->fl_owner;
> > > +			if (dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker)) {
> > > +				spin_unlock(&ctx->flc_lock);
> > > +				return 0;
> > > +			}
> > > +			spin_unlock(&ctx->flc_lock);
> > > +			status = nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
> > > +			if (status != nfserr_jukebox ||
> > > +					!nfsd_wait_for_delegreturn(rqstp, inode))
> > > +				return status;
> > > +			return 0;
> > > +		}
> > > +		break;
> > > +	}
> > > +	spin_unlock(&ctx->flc_lock);
> > > +	return 0;
> > > +}
> > 
> > If there is a lease held by a userland program (e.g. Samba), why don't
> > you want to break it here? Shouldn't it also be broken in this case?
> 
> okay, I will make the change to also break non-nfs lease with F_WRLCK.
> 

Sounds good.

> > 
> > I think this logic may be wrong. ISTM that you want to basically always
> > call nfsd_open_break_lease, unless it's a delegation held by the same
> > client.
> 
> I don't think we need to break any lease with F_RDLCK.
> 

Correct. To be clear: break any write lease unless it's a write
delegation held by the same client.

> 
> > 
> > 
> > > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > > index b83954fc57e3..4590b893dbc8 100644
> > > --- a/fs/nfsd/nfs4xdr.c
> > > +++ b/fs/nfsd/nfs4xdr.c
> > > @@ -2970,6 +2970,11 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
> > >   		if (status)
> > >   			goto out;
> > >   	}
> > > +	if (bmval0 & (FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE)) {
> > > +		status = nfsd4_deleg_getattr_conflict(rqstp, d_inode(dentry));
> > > +		if (status)
> > > +			goto out;
> > > +	}
> > >   
> > >   	err = vfs_getattr(&path, &stat,
> > >   			  STATX_BASIC_STATS | STATX_BTIME | STATX_CHANGE_COOKIE,
> > > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> > > index d49d3060ed4f..cbddcf484dba 100644
> > > --- a/fs/nfsd/state.h
> > > +++ b/fs/nfsd/state.h
> > > @@ -732,4 +732,7 @@ static inline bool try_to_expire_client(struct nfs4_client *clp)
> > >   	cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);
> > >   	return clp->cl_state == NFSD4_EXPIRABLE;
> > >   }
> > > +
> > > +extern __be32 nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp,
> > > +				struct inode *inode);
> > >   #endif   /* NFSD4_STATE_H */

-- 
Jeff Layton <jlayton@kernel.org>