Re: [PATCH v6 07/10] NFSD create new stateid for async copy

[bfields@fieldses.org (J. Bruce Fields)]

On Tue, Oct 24, 2017 at 01:47:49PM -0400, Olga Kornievskaia wrote:
> Generate a new stateid to be used for reply to the asynchronous
> COPY (this would also be used later by COPY_NOTIFY as well).
> Associate the stateid with the parent OPEN/LOCK/DELEG stateid
> that can be freed during the free of the parent stateid. However,
> right now deciding to bind the lifetime to when the vfs copy
> is done. This way don't need to keep the nfsd_net structure for
> the callback. The drawback is that time copy state information
> is available for query by OFFLOAD_STATUS is slightly less.
> 
> Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
> ---
>  fs/nfsd/netns.h     |  8 +++++++
>  fs/nfsd/nfs4proc.c  | 32 +++++++++++++++++++-------
>  fs/nfsd/nfs4state.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/nfsd/nfsctl.c    |  1 +
>  fs/nfsd/state.h     | 14 ++++++++++++
>  fs/nfsd/xdr4.h      |  2 ++
>  6 files changed, 115 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
> index 3714231..2c88a95 100644
> --- a/fs/nfsd/netns.h
> +++ b/fs/nfsd/netns.h
> @@ -119,6 +119,14 @@ struct nfsd_net {
>  	u32 clverifier_counter;
>  
>  	struct svc_serv *nfsd_serv;
> +
> +	/*
> +	 * clientid and stateid data for construction of net unique COPY
> +	 * stateids.
> +	 */
> +	u32		s2s_cp_cl_id;
> +	struct idr	s2s_cp_stateids;
> +	spinlock_t	s2s_cp_lock;
>  };
>  
>  /* Simple check to find out if a given net was properly initialized */
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index a020533..6876080 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -1039,7 +1039,8 @@ static int fill_in_write_vector(struct kvec *vec, struct nfsd4_write *write)
>  static __be32
>  nfsd4_verify_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  		  stateid_t *src_stateid, struct file **src,
> -		  stateid_t *dst_stateid, struct file **dst)
> +		  stateid_t *dst_stateid, struct file **dst,
> +		  struct nfs4_stid **stid)
>  {
>  	__be32 status;
>  
> @@ -1053,7 +1054,7 @@ static int fill_in_write_vector(struct kvec *vec, struct nfsd4_write *write)
>  
>  	status = nfs4_preprocess_stateid_op(rqstp, cstate, &cstate->current_fh,
>  					    dst_stateid, WR_STATE, dst, NULL,
> -					    NULL);
> +					    stid);
>  	if (status) {
>  		dprintk("NFSD: %s: couldn't process dst stateid!\n", __func__);
>  		goto out_put_src;
> @@ -1084,7 +1085,7 @@ static int fill_in_write_vector(struct kvec *vec, struct nfsd4_write *write)
>  	__be32 status;
>  
>  	status = nfsd4_verify_copy(rqstp, cstate, &clone->cl_src_stateid, &src,
> -				   &clone->cl_dst_stateid, &dst);
> +				   &clone->cl_dst_stateid, &dst, NULL);
>  	if (status)
>  		goto out;
>  
> @@ -1117,8 +1118,6 @@ static int nfsd4_cb_offload_done(struct nfsd4_callback *cb,
>  
>  static int nfsd4_init_copy_res(struct nfsd4_copy *copy, bool sync)
>  {
> -	memcpy(&copy->cp_res.cb_stateid, &copy->cp_dst_stateid,
> -		sizeof(copy->cp_dst_stateid));
>  	copy->cp_res.wr_stable_how = NFS_UNSTABLE;
>  	copy->cp_consecutive = 1;
>  	copy->cp_synchronous = sync;
> @@ -1180,10 +1179,15 @@ static void dup_copy_fields(struct nfsd4_copy *src, struct nfsd4_copy *dst)
>  	atomic_inc(&dst->cp_clp->cl_refcount);
>  	dst->fh_dst = get_file(src->fh_dst);
>  	dst->fh_src = get_file(src->fh_src);
> +	dst->stid = src->stid;
> +	dst->cps = src->cps;
>  }
>  
>  static void cleanup_async_copy(struct nfsd4_copy *copy)
>  {
> +	list_del(&copy->cps->cp_list);
> +	nfs4_free_cp_state(copy->cps);
> +	nfs4_put_stid(copy->stid);
>  	fput(copy->fh_dst);
>  	fput(copy->fh_src);
>  	spin_lock(&copy->cp_clp->async_lock);
> @@ -1225,7 +1229,7 @@ static int nfsd4_do_async_copy(void *data)
>  
>  	status = nfsd4_verify_copy(rqstp, cstate, &copy->cp_src_stateid,
>  				   &copy->fh_src, &copy->cp_dst_stateid,
> -				   &copy->fh_dst);
> +				   &copy->fh_dst, &copy->stid);
>  	if (status)
>  		goto out;
>  
> @@ -1234,15 +1238,27 @@ static int nfsd4_do_async_copy(void *data)
>  		sizeof(struct knfsd_fh));
>  	copy->net = SVC_NET(rqstp);
>  	if (!copy->cp_synchronous) {
> +		struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
> +
>  		status = nfsd4_init_copy_res(copy, 0);
>  		async_copy = kzalloc(sizeof(struct nfsd4_copy), GFP_KERNEL);
>  		if (!async_copy) {
>  			status = nfserrno(-ENOMEM);
>  			goto out;
>  		}
> +		copy->cps = nfs4_alloc_init_cp_state(nn, copy->stid);
> +		if (!copy->cps) {
> +			status = nfserrno(-ENOMEM);
> +			kfree(async_copy);
> +			goto out;
> +		}
> +		/* take a reference on the parent stateid so it's not
> +		 * not freed by the copy compound
> +		 */
> +		atomic_inc(&copy->stid->sc_count);
> +		memcpy(&copy->cp_res.cb_stateid, &copy->cps->cp_stateid,
> +			sizeof(copy->cps->cp_stateid));
>  		dup_copy_fields(copy, async_copy);
> -		memcpy(&copy->cp_res.cb_stateid, &copy->cp_dst_stateid,
> -			sizeof(copy->cp_dst_stateid));
>  		spin_lock(&async_copy->cp_clp->async_lock);
>  		list_add(&async_copy->copies,
>  				&async_copy->cp_clp->async_copies);
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index af40762..f9151f2 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -658,6 +658,7 @@ struct nfs4_stid *nfs4_alloc_stid(struct nfs4_client *cl, struct kmem_cache *sla
>  	/* Will be incremented before return to client: */
>  	atomic_set(&stid->sc_count, 1);
>  	spin_lock_init(&stid->sc_lock);
> +	INIT_LIST_HEAD(&stid->sc_cp_list);
>  
>  	/*
>  	 * It shouldn't be a problem to reuse an opaque stateid value.
> @@ -674,6 +675,66 @@ struct nfs4_stid *nfs4_alloc_stid(struct nfs4_client *cl, struct kmem_cache *sla
>  	return NULL;
>  }
>  
> +/*
> + * Create a unique stateid_t to represent each COPY. Hang the copy
> + * stateids off the OPEN/LOCK/DELEG stateid from the client open
> + * the source file.
> + */
> +struct nfs4_cp_state *nfs4_alloc_init_cp_state(struct nfsd_net *nn,
> +					       struct nfs4_stid *p_stid)
> +{
> +	struct nfs4_cp_state *cps;
> +	int new_id;
> +
> +	cps = kzalloc(sizeof(struct nfs4_cp_state), GFP_KERNEL);
> +	if (!cps)
> +		return NULL;
> +	idr_preload(GFP_KERNEL);
> +	spin_lock(&nn->s2s_cp_lock);
> +	new_id = idr_alloc_cyclic(&nn->s2s_cp_stateids, cps, 0, 0, GFP_NOWAIT);
> +	spin_unlock(&nn->s2s_cp_lock);
> +	idr_preload_end();
> +	if (new_id < 0)
> +		goto out_free;
> +	cps->cp_stateid.si_opaque.so_id = new_id;
> +	cps->cp_stateid.si_opaque.so_clid.cl_boot = nn->boot_time;
> +	cps->cp_stateid.si_opaque.so_clid.cl_id = nn->s2s_cp_cl_id;
> +	cps->cp_p_stid = p_stid;
> +	INIT_LIST_HEAD(&cps->cp_list);
> +	list_add(&cps->cp_list, &p_stid->sc_cp_list);
> +
> +	return cps;
> +out_free:
> +	kfree(cps);
> +	return NULL;
> +}
> +
> +void nfs4_free_cp_state(struct nfs4_cp_state *cps)
> +{
> +	struct nfsd_net *nn;
> +
> +	nn = net_generic(cps->cp_p_stid->sc_client->net, nfsd_net_id);
> +	spin_lock(&nn->s2s_cp_lock);
> +	idr_remove(&nn->s2s_cp_stateids, cps->cp_stateid.si_opaque.so_id);
> +	spin_unlock(&nn->s2s_cp_lock);
> +
> +	kfree(cps);
> +}
> +
> +static void nfs4_free_cp_statelist(struct nfs4_stid *stid)
> +{
> +	struct nfs4_cp_state *cps;
> +
> +	might_sleep();
> +
> +	while (!list_empty(&stid->sc_cp_list)) {
> +		cps = list_first_entry(&stid->sc_cp_list, struct nfs4_cp_state,
> +				       cp_list);
> +		list_del(&cps->cp_list);
> +		nfs4_free_cp_state(cps);
> +	}
> +}
> +
>  static struct nfs4_ol_stateid * nfs4_alloc_open_stateid(struct nfs4_client *clp)
>  {
>  	struct nfs4_stid *stid;
> @@ -819,6 +880,9 @@ static void block_delegations(struct knfsd_fh *fh)
>  	}
>  	idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
>  	spin_unlock(&clp->cl_lock);
> +
> +	nfs4_free_cp_statelist(s);

Is this really safe if there are still ongoing copies?

I think the copies take a reference count on the parent stateid, so I
think we should never actually get here: perhaps this could just be a
WARN_ON(!list_empty(&s->s_cp_list)).  Though nfsd4_copy puts things on
this list before bumping the sc_count, so there may be a race there.

What is supposed to happen, by the way, if a close arrives for a stateid
with a copy in progress?  Do we cancel the copy before returning from
the close, or do we fail the close?  (Same question for unlock and
delegation return, I guess.)

--b.