On Fri, 2024-07-26 at 09:54 -0400, Jeff Layton wrote:
> On Wed, 2024-07-24 at 10:01 -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);
>
> In the case where we have multiple stateids for this client, are we
> guaranteed to get back the delegation stateid here? What if we get
> back
> the open stateid for the O_WRONLY open instead?
>
Oh, duh -- disregard this. We're looking for a specific stateid here,
so if the client sends a delegation stateid, that's what we'll find.
>
> > + /*
> > + * 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;
> > + }
^^^
I do agree with Chuck that this looks sketchy.
> > 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 {
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
