On Wed, Jul 24, 2024 at 10:01:38AM -0700, Sagi Grimberg wrote:
> Based on a patch fom Dai Ngo, allow NFSv4 client to use write delegation
> stateid for READ operation. Per RFC 8881 section 9.1.2. Use of the
> Stateid and Locking.
>
> In addition, for anonymous stateids, check for pending delegations by
> the filehandle and client_id, and if a conflict found, recall the delegation
> before allowing the read to take place.
>
> Suggested-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
> Signed-off-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
> ---
> fs/nfsd/nfs4proc.c | 22 +++++++++++++++++++--
> fs/nfsd/nfs4state.c | 47 +++++++++++++++++++++++++++++++++++++++++++++
> fs/nfsd/nfs4xdr.c | 9 +++++++++
> fs/nfsd/state.h | 2 ++
> fs/nfsd/xdr4.h | 2 ++
> 5 files changed, 80 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 7b70309ad8fb..324984ec70c6 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -979,8 +979,24 @@ nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> /* check stateid */
> status = nfs4_preprocess_stateid_op(rqstp, cstate, &cstate->current_fh,
> &read->rd_stateid, RD_STATE,
> - &read->rd_nf, NULL);
> -
> + &read->rd_nf, &read->rd_wd_stid);
> + /*
> + * rd_wd_stid is needed for nfsd4_encode_read to allow write
> + * delegation stateid used for read. Its refcount is decremented
> + * by nfsd4_read_release when read is done.
> + */
> + if (!status) {
> + if (!read->rd_wd_stid) {
> + /* special stateid? */
> + status = nfsd4_deleg_read_conflict(rqstp, cstate->clp,
> + &cstate->current_fh);
> + } else if (read->rd_wd_stid->sc_type != SC_TYPE_DELEG ||
> + delegstateid(read->rd_wd_stid)->dl_type !=
> + NFS4_OPEN_DELEGATE_WRITE) {
> + nfs4_put_stid(read->rd_wd_stid);
> + read->rd_wd_stid = NULL;
> + }
> + }
> read->rd_rqstp = rqstp;
> read->rd_fhp = &cstate->current_fh;
> return status;
> @@ -990,6 +1006,8 @@ nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> static void
> nfsd4_read_release(union nfsd4_op_u *u)
> {
> + if (u->read.rd_wd_stid)
> + nfs4_put_stid(u->read.rd_wd_stid);
> if (u->read.rd_nf)
> nfsd_file_put(u->read.rd_nf);
> trace_nfsd_read_done(u->read.rd_rqstp, u->read.rd_fhp,
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index dc61a8adfcd4..7e6b9fb31a4c 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -8805,6 +8805,53 @@ nfsd4_get_writestateid(struct nfsd4_compound_state *cstate,
> get_stateid(cstate, &u->write.wr_stateid);
> }
>
> +/**
> + * nfsd4_deleg_read_conflict - Recall if read causes conflict
> + * @rqstp: RPC transaction context
> + * @clp: nfs client
> + * @fhp: nfs file handle
> + * @inode: file to be checked for a conflict
> + * @modified: return true if file was modified
> + * @size: new size of file if modified is true
> + *
> + * This function is called when there is a conflict between a write
> + * delegation and a read that is using a special stateid where the
> + * we cannot derive the client stateid exsistence. The server
> + * must recall a conflicting delegation before allowing the read
> + * to continue.
> + *
> + * Returns 0 if there is no conflict; otherwise an nfs_stat
> + * code is returned.
> + */
> +__be32 nfsd4_deleg_read_conflict(struct svc_rqst *rqstp,
> + struct nfs4_client *clp, struct svc_fh *fhp)
> +{
> + struct nfs4_file *fp;
> + __be32 status = 0;
> +
> + fp = nfsd4_file_hash_lookup(fhp);
> + if (!fp)
> + return nfs_ok;
> +
> + spin_lock(&state_lock);
> + spin_lock(&fp->fi_lock);
> + if (!list_empty(&fp->fi_delegations) &&
> + !nfs4_delegation_exists(clp, fp)) {
> + /* conflict, recall deleg */
> + status = nfserrno(nfsd_open_break_lease(fp->fi_inode,
> + NFSD_MAY_READ));
> + if (status)
> + goto out;
> + if (!nfsd_wait_for_delegreturn(rqstp, fp->fi_inode))
> + status = nfserr_jukebox;
> + }
> +out:
> + spin_unlock(&fp->fi_lock);
> + spin_unlock(&state_lock);
> + return status;
> +}
> +
> +
> /**
> * nfsd4_deleg_getattr_conflict - Recall if GETATTR causes conflict
> * @rqstp: RPC transaction context
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index c7bfd2180e3f..f0fe526fac3c 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -4418,6 +4418,7 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
> unsigned long maxcount;
> struct file *file;
> __be32 *p;
> + fmode_t o_fmode = 0;
>
> if (nfserr)
> return nfserr;
> @@ -4437,10 +4438,18 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
> maxcount = min_t(unsigned long, read->rd_length,
> (xdr->buf->buflen - xdr->buf->len));
>
> + if (read->rd_wd_stid) {
> + /* allow READ using write delegation stateid */
> + o_fmode = file->f_mode;
> + file->f_mode |= FMODE_READ;
> + }
nfsd4_encode_read_plus() needs to handle write delegation stateids
as well.
I'm not too sure about modifying the f_mode on an nfsd_file you
just got from a cache of shared nfsd_files.
I think I'd prefer if preprocess_stateid returned an nfsd_file that
was already open for read. IIUC that would mean that no changes
would be needed here or in nfsd4_encode_read_plus().
Would that be difficult?
> if (file->f_op->splice_read && splice_ok)
> nfserr = nfsd4_encode_splice_read(resp, read, file, maxcount);
> else
> nfserr = nfsd4_encode_readv(resp, read, file, maxcount);
> + if (o_fmode)
> + file->f_mode = o_fmode;
> +
> if (nfserr) {
> xdr_truncate_encode(xdr, starting_len);
> return nfserr;
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index ffc217099d19..c1f13b5877c6 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -780,6 +780,8 @@ static inline bool try_to_expire_client(struct nfs4_client *clp)
> return clp->cl_state == NFSD4_EXPIRABLE;
> }
>
> +extern __be32 nfsd4_deleg_read_conflict(struct svc_rqst *rqstp,
> + struct nfs4_client *clp, struct svc_fh *fhp);
> extern __be32 nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp,
> struct inode *inode, bool *file_modified, u64 *size);
> #endif /* NFSD4_STATE_H */
> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
> index fbdd42cde1fa..434973a6a8b1 100644
> --- a/fs/nfsd/xdr4.h
> +++ b/fs/nfsd/xdr4.h
> @@ -426,6 +426,8 @@ struct nfsd4_read {
> struct svc_rqst *rd_rqstp; /* response */
> struct svc_fh *rd_fhp; /* response */
> u32 rd_eof; /* response */
> +
> + struct nfs4_stid *rd_wd_stid; /* internal */
> };
>
> struct nfsd4_readdir {
> --
> 2.43.0
>
--
Chuck Lever
