Re: [PATCH v5 2/3] NFSD: handle GETATTR conflict with write delegation

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2023-05-22 at 16:52 -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 and NFS4ERR_DELAY is returned
> for the GETATTR.
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4state.c | 37 +++++++++++++++++++++++++++++++++++++
>  fs/nfsd/nfs4xdr.c   |  5 +++++
>  fs/nfsd/state.h     |  3 +++
>  3 files changed, 45 insertions(+)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index b90b74a5e66e..ea9cd781db5f 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -8353,3 +8353,40 @@ nfsd4_get_writestateid(struct nfsd4_compound_state *cstate,
>  {
>  	get_stateid(cstate, &u->write.wr_stateid);
>  }
> +
> +__be32
> +nfs4_handle_wrdeleg_conflict(struct svc_rqst *rqstp, struct inode *inode)
> +{
> +	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;
> +			/*
> +			 * increment the sc_count to prevent the delegation to
> +			 * be freed while sending the CB_RECALL. The refcount is
> +			 * decremented by nfs4_put_stid in nfsd4_cb_recall_release
> +			 * after the request was sent.
> +			 */
> +			if (dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker) ||
> +					!refcount_inc_not_zero(&dp->dl_stid.sc_count)) {

I still don't get why you're incrementing the refcount of this stateid.
At this point, you know that this stateid is owned by a different client
altogether,  and breaking its lease doesn't require a reference to the
stateid.

I think this will cause a refcount leak.

> +				spin_unlock(&ctx->flc_lock);
> +				return 0;
> +			}
> +			spin_unlock(&ctx->flc_lock);
> +			return nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
> +		}
> +		break;
> +	}
> +	spin_unlock(&ctx->flc_lock);
> +	return 0;
> +}
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 76db2fe29624..ed09b575afac 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2966,6 +2966,11 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>  		if (status)
>  			goto out;
>  	}
> +	if (bmval0 & (FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE)) {
> +		status = nfs4_handle_wrdeleg_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..64727a39f0db 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 nfs4_handle_wrdeleg_conflict(struct svc_rqst *rqstp,
> +				struct inode *inode);
>  #endif   /* NFSD4_STATE_H */

-- 
Jeff Layton <jlayton@kernel.org>