Re: [PATCH 1/6] nfsd: prepare for supporting admin-revocation of state

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2023-11-03 at 07:03 +1100, NeilBrown wrote:
> On Thu, 02 Nov 2023, Jeff Layton wrote:
> > On Wed, 2023-11-01 at 11:57 +1100, NeilBrown wrote:
> > > The NFSv4 protocol allows state to be revoked by the admin and has error
> > > codes which allow this to be communicated to the client.
> > > 
> > > This patch
> > >  - introduces 3 new state-id types for revoked open, lock, and
> > >    delegation state.  This requires the bitmask to be 'short',
> > >    not 'char'
> > >  - reports NFS4ERR_ADMIN_REVOKED when these are accessed
> > >  - introduces a per-client counter of these states and returns
> > >    SEQ4_STATUS_ADMIN_STATE_REVOKED when the counter is not zero.
> > >    Decrement this when freeing any admin-revoked state.
> > >  - introduces stub code to find all interesting states for a given
> > >    superblock so they can be revoked via the 'unlock_filesystem'
> > >    file in /proc/fs/nfsd/
> > >    No actual states are handled yet.
> > > 
> > > Signed-off-by: NeilBrown <neilb@suse.de>
> > > ---
> > >  fs/nfsd/nfs4layouts.c |  2 +-
> > >  fs/nfsd/nfs4state.c   | 93 +++++++++++++++++++++++++++++++++++++++----
> > >  fs/nfsd/nfsctl.c      |  1 +
> > >  fs/nfsd/nfsd.h        |  1 +
> > >  fs/nfsd/state.h       | 35 +++++++++++-----
> > >  fs/nfsd/trace.h       |  8 +++-
> > >  6 files changed, 120 insertions(+), 20 deletions(-)
> > > 
> > > diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
> > > index 5e8096bc5eaa..09d0363bfbc4 100644
> > > --- a/fs/nfsd/nfs4layouts.c
> > > +++ b/fs/nfsd/nfs4layouts.c
> > > @@ -269,7 +269,7 @@ nfsd4_preprocess_layout_stateid(struct svc_rqst *rqstp,
> > >  {
> > >  	struct nfs4_layout_stateid *ls;
> > >  	struct nfs4_stid *stid;
> > > -	unsigned char typemask = NFS4_LAYOUT_STID;
> > > +	unsigned short typemask = NFS4_LAYOUT_STID;
> > >  	__be32 status;
> > >  
> > >  	if (create)
> > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > > index 65fd5510323a..f3ba53a16105 100644
> > > --- a/fs/nfsd/nfs4state.c
> > > +++ b/fs/nfsd/nfs4state.c
> > > @@ -1202,6 +1202,13 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
> > >  	return NULL;
> > >  }
> > >  
> > > +void nfs4_unhash_stid(struct nfs4_stid *s)
> > > +{
> > > +	if (s->sc_type & NFS4_ALL_ADMIN_REVOKED_STIDS)
> > > +		atomic_dec(&s->sc_client->cl_admin_revoked);
> > > +	s->sc_type = 0;
> > > +}
> > > +
> > >  void
> > >  nfs4_put_stid(struct nfs4_stid *s)
> > >  {
> > > @@ -1215,6 +1222,7 @@ nfs4_put_stid(struct nfs4_stid *s)
> > >  		return;
> > >  	}
> > >  	idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
> > > +	nfs4_unhash_stid(s);
> > >  	nfs4_free_cpntf_statelist(clp->net, s);
> > >  	spin_unlock(&clp->cl_lock);
> > >  	s->sc_free(s);
> > > @@ -1265,11 +1273,6 @@ static void destroy_unhashed_deleg(struct nfs4_delegation *dp)
> > >  	nfs4_put_stid(&dp->dl_stid);
> > >  }
> > >  
> > > -void nfs4_unhash_stid(struct nfs4_stid *s)
> > > -{
> > > -	s->sc_type = 0;
> > > -}
> > > -
> > >  /**
> > >   * nfs4_delegation_exists - Discover if this delegation already exists
> > >   * @clp:     a pointer to the nfs4_client we're granting a delegation to
> > > @@ -1536,6 +1539,7 @@ static void put_ol_stateid_locked(struct nfs4_ol_stateid *stp,
> > >  	}
> > >  
> > >  	idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
> > > +	nfs4_unhash_stid(s);
> > >  	list_add(&stp->st_locks, reaplist);
> > >  }
> > >  
> > > @@ -1680,6 +1684,53 @@ static void release_openowner(struct nfs4_openowner *oo)
> > >  	nfs4_put_stateowner(&oo->oo_owner);
> > >  }
> > >  
> > > +static struct nfs4_stid *find_one_sb_stid(struct nfs4_client *clp,
> > > +					  struct super_block *sb,
> > > +					  unsigned short sc_types)
> > > +{
> > > +	unsigned long id, tmp;
> > > +	struct nfs4_stid *stid;
> > > +
> > > +	spin_lock(&clp->cl_lock);
> > > +	idr_for_each_entry_ul(&clp->cl_stateids, stid, tmp, id)
> > > +		if ((stid->sc_type & sc_types) &&
> > > +		    stid->sc_file->fi_inode->i_sb == sb) {
> > > +			refcount_inc(&stid->sc_count);
> > > +			break;
> > > +		}
> > > +	spin_unlock(&clp->cl_lock);
> > > +	return stid;
> > > +}
> > > +
> > > +void nfsd4_revoke_states(struct net *net, struct super_block *sb)
> > > +{
> > > +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > > +	unsigned int idhashval;
> > > +	unsigned short sc_types;
> > > +
> > > +	sc_types = 0;
> > > +
> > > +	spin_lock(&nn->client_lock);
> > > +	for (idhashval = 0; idhashval < CLIENT_HASH_MASK; idhashval++) {
> > > +		struct list_head *head = &nn->conf_id_hashtbl[idhashval];
> > > +		struct nfs4_client *clp;
> > > +	retry:
> > > +		list_for_each_entry(clp, head, cl_idhash) {
> > > +			struct nfs4_stid *stid = find_one_sb_stid(clp, sb,
> > > +								  sc_types);
> > > +			if (stid) {
> > > +				spin_unlock(&nn->client_lock);
> > > +				switch (stid->sc_type) {
> > > +				}
> > > +				nfs4_put_stid(stid);
> > > +				spin_lock(&nn->client_lock);
> > > +				goto retry;
> > > +			}
> > > +		}
> > > +	}
> > > +	spin_unlock(&nn->client_lock);
> > > +}
> > > +
> > >  static inline int
> > >  hash_sessionid(struct nfs4_sessionid *sessionid)
> > >  {
> > > @@ -2465,7 +2516,8 @@ find_stateid_locked(struct nfs4_client *cl, stateid_t *t)
> > >  }
> > >  
> > >  static struct nfs4_stid *
> > > -find_stateid_by_type(struct nfs4_client *cl, stateid_t *t, char typemask)
> > > +find_stateid_by_type(struct nfs4_client *cl, stateid_t *t,
> > > +		     unsigned short typemask)
> > >  {
> > >  	struct nfs4_stid *s;
> > >  
> > > @@ -2549,6 +2601,8 @@ static int client_info_show(struct seq_file *m, void *v)
> > >  	}
> > >  	seq_printf(m, "callback state: %s\n", cb_state2str(clp->cl_cb_state));
> > >  	seq_printf(m, "callback address: %pISpc\n", &clp->cl_cb_conn.cb_addr);
> > > +	seq_printf(m, "admin-revoked states: %d\n",
> > > +		   atomic_read(&clp->cl_admin_revoked));
> > >  	drop_client(clp);
> > >  
> > >  	return 0;
> > > @@ -4108,6 +4162,8 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> > >  	}
> > >  	if (!list_empty(&clp->cl_revoked))
> > >  		seq->status_flags |= SEQ4_STATUS_RECALLABLE_STATE_REVOKED;
> > > +	if (atomic_read(&clp->cl_admin_revoked))
> > > +		seq->status_flags |= SEQ4_STATUS_ADMIN_STATE_REVOKED;
> > >  out_no_session:
> > >  	if (conn)
> > >  		free_conn(conn);
> > > @@ -5200,6 +5256,11 @@ nfs4_check_deleg(struct nfs4_client *cl, struct nfsd4_open *open,
> > >  			status = nfserr_deleg_revoked;
> > >  		goto out;
> > >  	}
> > > +	if (deleg->dl_stid.sc_type == NFS4_ADMIN_REVOKED_DELEG_STID) {
> > > +		nfs4_put_stid(&deleg->dl_stid);
> > > +		status = nfserr_admin_revoked;
> > > +		goto out;
> > > +	}
> > >  	flags = share_access_to_flags(open->op_share_access);
> > >  	status = nfs4_check_delegmode(deleg, flags);
> > >  	if (status) {
> > > @@ -6478,6 +6539,11 @@ static __be32 nfsd4_validate_stateid(struct nfs4_client *cl, stateid_t *stateid)
> > >  	case NFS4_REVOKED_DELEG_STID:
> > >  		status = nfserr_deleg_revoked;
> > >  		break;
> > > +	case NFS4_ADMIN_REVOKED_STID:
> > > +	case NFS4_ADMIN_REVOKED_LOCK_STID:
> > > +	case NFS4_ADMIN_REVOKED_DELEG_STID:
> > > +		status = nfserr_admin_revoked;
> > > +		break;
> > >  	case NFS4_OPEN_STID:
> > >  	case NFS4_LOCK_STID:
> > >  		status = nfsd4_check_openowner_confirmed(openlockstateid(s));
> > > @@ -6496,7 +6562,7 @@ static __be32 nfsd4_validate_stateid(struct nfs4_client *cl, stateid_t *stateid)
> > >  
> > >  __be32
> > >  nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
> > > -		     stateid_t *stateid, unsigned char typemask,
> > > +		     stateid_t *stateid, unsigned short typemask,
> > >  		     struct nfs4_stid **s, struct nfsd_net *nn)
> > >  {
> > >  	__be32 status;
> > > @@ -6512,6 +6578,13 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
> > >  	else if (typemask & NFS4_DELEG_STID)
> > >  		typemask |= NFS4_REVOKED_DELEG_STID;
> > >  
> > > +	if (typemask & NFS4_OPEN_STID)
> > > +		typemask |= NFS4_ADMIN_REVOKED_STID;
> > > +	if (typemask & NFS4_LOCK_STID)
> > > +		typemask |= NFS4_ADMIN_REVOKED_LOCK_STID;
> > > +	if (typemask & NFS4_DELEG_STID)
> > > +		typemask |= NFS4_ADMIN_REVOKED_DELEG_STID;
> > > +
> > >  	if (ZERO_STATEID(stateid) || ONE_STATEID(stateid) ||
> > >  		CLOSE_STATEID(stateid))
> > >  		return nfserr_bad_stateid;
> > > @@ -6532,6 +6605,10 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
> > >  			return nfserr_deleg_revoked;
> > >  		return nfserr_bad_stateid;
> > >  	}
> > > +	if (stid->sc_type & NFS4_ALL_ADMIN_REVOKED_STIDS) {
> > > +		nfs4_put_stid(stid);
> > > +		return nfserr_admin_revoked;
> > > +	}
> > >  	*s = stid;
> > >  	return nfs_ok;
> > >  }
> > > @@ -6899,7 +6976,7 @@ static __be32 nfs4_seqid_op_checks(struct nfsd4_compound_state *cstate, stateid_
> > >   */
> > >  static __be32
> > >  nfs4_preprocess_seqid_op(struct nfsd4_compound_state *cstate, u32 seqid,
> > > -			 stateid_t *stateid, char typemask,
> > > +			 stateid_t *stateid, unsigned short typemask,
> > >  			 struct nfs4_ol_stateid **stpp,
> > >  			 struct nfsd_net *nn)
> > >  {
> > > diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> > > index 739ed5bf71cd..50368eec86b0 100644
> > > --- a/fs/nfsd/nfsctl.c
> > > +++ b/fs/nfsd/nfsctl.c
> > > @@ -281,6 +281,7 @@ static ssize_t write_unlock_fs(struct file *file, char *buf, size_t size)
> > >  	 * 3.  Is that directory the root of an exported file system?
> > >  	 */
> > >  	error = nlmsvc_unlock_all_by_sb(path.dentry->d_sb);
> > > +	nfsd4_revoke_states(netns(file), path.dentry->d_sb);
> > >  
> > >  	path_put(&path);
> > >  	return error;
> > > diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> > > index f5ff42f41ee7..d46203eac3c8 100644
> > > --- a/fs/nfsd/nfsd.h
> > > +++ b/fs/nfsd/nfsd.h
> > > @@ -280,6 +280,7 @@ void		nfsd_lockd_shutdown(void);
> > >  #define	nfserr_no_grace		cpu_to_be32(NFSERR_NO_GRACE)
> > >  #define	nfserr_reclaim_bad	cpu_to_be32(NFSERR_RECLAIM_BAD)
> > >  #define	nfserr_badname		cpu_to_be32(NFSERR_BADNAME)
> > > +#define	nfserr_admin_revoked	cpu_to_be32(NFS4ERR_ADMIN_REVOKED)
> > >  #define	nfserr_cb_path_down	cpu_to_be32(NFSERR_CB_PATH_DOWN)
> > >  #define	nfserr_locked		cpu_to_be32(NFSERR_LOCKED)
> > >  #define	nfserr_wrongsec		cpu_to_be32(NFSERR_WRONGSEC)
> > > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> > > index f96eaa8e9413..3af5ab55c978 100644
> > > --- a/fs/nfsd/state.h
> > > +++ b/fs/nfsd/state.h
> > > @@ -88,17 +88,23 @@ struct nfsd4_callback_ops {
> > >   */
> > >  struct nfs4_stid {
> > >  	refcount_t		sc_count;
> > > -#define NFS4_OPEN_STID 1
> > > -#define NFS4_LOCK_STID 2
> > > -#define NFS4_DELEG_STID 4
> > > +	struct list_head	sc_cp_list;
> > > +	unsigned short		sc_type;
> > 
> > Should we just go ahead and make this a full 32-bit word? We seem to
> > keep adding flags to this field, and I doubt we're saving anything by
> > making this a short.
> > 
> > > +#define NFS4_OPEN_STID			BIT(0)
> > > +#define NFS4_LOCK_STID			BIT(1)
> > > +#define NFS4_DELEG_STID			BIT(2)
> > >  /* For an open stateid kept around *only* to process close replays: */
> > > -#define NFS4_CLOSED_STID 8
> > > +#define NFS4_CLOSED_STID		BIT(3)
> > >  /* For a deleg stateid kept around only to process free_stateid's: */
> > > -#define NFS4_REVOKED_DELEG_STID 16
> > > -#define NFS4_CLOSED_DELEG_STID 32
> > > -#define NFS4_LAYOUT_STID 64
> > > -	struct list_head	sc_cp_list;
> > > -	unsigned char		sc_type;
> > > +#define NFS4_REVOKED_DELEG_STID		BIT(4)
> > > +#define NFS4_CLOSED_DELEG_STID		BIT(5)
> > > +#define NFS4_LAYOUT_STID		BIT(6)
> > > +#define NFS4_ADMIN_REVOKED_STID		BIT(7)
> > > +#define NFS4_ADMIN_REVOKED_LOCK_STID	BIT(8)
> > > +#define NFS4_ADMIN_REVOKED_DELEG_STID	BIT(9)
> > > +#define NFS4_ALL_ADMIN_REVOKED_STIDS (NFS4_ADMIN_REVOKED_STID |		\
> > > +				     NFS4_ADMIN_REVOKED_LOCK_STID |	\
> > > +				     NFS4_ADMIN_REVOKED_DELEG_STID)
> > 
> > Not a specific criticism of these patches, since this problem preexists
> > them, but I really dislike the way that sc_type is used as a bitmask,
> > but also sort of like an enum. In some cases, we test for specific flags
> > in the mask, and in other cases (e.g. states_show), we treat them as
> > discrete values to feed it to a switch().
> > 
> > Personally, I'd find this less confusing if we just treat this as a set
> > of flags full-stop. We could leave the low-order bits to show the real
> > type (open, lock, deleg, etc.) and just mask off the high-order bits
> > when we need to feed it to a switch statement.
> > 
> > For instance above, we're adding 3 new NFS4_ADMIN_REVOKED values, but we
> > could (in theory) just have a flag in there that says NFS4_ADMIN_REVOKED
> > and leave the old type bit in place instead of changing it to a new
> > discrete sc_type value.
> 
> I agree.
> Bits might be:
>     OPEN
>     LOCK
>     DELEG
>     LAYOUT
>     CLOSED (combines with OPEN or DELEG)
>     REVOKED (combines with DELEG)
>     ADMIN_REVOKED (combined with OPEN, LOCK, DELEG.  Sets REVOKED when
>                    with DELEG)
> 
> so we could go back to a char :-)  Probably sensible to use unsigned int
> though.
> 

Yeah, a u32 would be best I think. It'll just fill an existing hole on
my box (x86_64), according to pahole:

	unsigned char              sc_type;              /*    24     1 */

	/* XXX 3 bytes hole, try to pack */

> For updates the rule would be that bits can be set but never cleared so
> you don't need locking to read unless you care about a bit that can be
> changed.
> 

Probably for the low order OPEN/LOCK/DELEG bits, the rule should be that
they never change. We can never convert from one to another since they
come out of different slabcaches. It's probably worthwhile to leave a
few low order bits carved out for new types in the future too. e.g.
directory delegations...

Maybe we should rename the field too? How about "sc_mode" since this is
starting to resemble the i_mode field in some ways (type and permissions
squashed together).

> cl_lock is held most often for updates, but not always.  We should see
> if we can make that more consistent.  Maybe we could use sc_lock
> instead.
> I'll have a look.
> 

Awesome.

> Thanks,
> NeilBrown
> 
> 
> > 
> > >  	stateid_t		sc_stateid;
> > >  	spinlock_t		sc_lock;
> > >  	struct nfs4_client	*sc_client;
> > > @@ -372,6 +378,7 @@ struct nfs4_client {
> > >  	clientid_t		cl_clientid;	/* generated by server */
> > >  	nfs4_verifier		cl_confirm;	/* generated by server */
> > >  	u32			cl_minorversion;
> > > +	atomic_t		cl_admin_revoked; /* count of admin-revoked states */
> > >  	/* NFSv4.1 client implementation id: */
> > >  	struct xdr_netobj	cl_nii_domain;
> > >  	struct xdr_netobj	cl_nii_name;
> > > @@ -694,7 +701,7 @@ extern __be32 nfs4_preprocess_stateid_op(struct svc_rqst *rqstp,
> > >  		stateid_t *stateid, int flags, struct nfsd_file **filp,
> > >  		struct nfs4_stid **cstid);
> > >  __be32 nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
> > > -		     stateid_t *stateid, unsigned char typemask,
> > > +		     stateid_t *stateid, unsigned short typemask,
> > >  		     struct nfs4_stid **s, struct nfsd_net *nn);
> > >  struct nfs4_stid *nfs4_alloc_stid(struct nfs4_client *cl, struct kmem_cache *slab,
> > >  				  void (*sc_free)(struct nfs4_stid *));
> > > @@ -736,6 +743,14 @@ static inline void get_nfs4_file(struct nfs4_file *fi)
> > >  }
> > >  struct nfsd_file *find_any_file(struct nfs4_file *f);
> > >  
> > > +#ifdef CONFIG_NFSD_V4
> > > +void nfsd4_revoke_states(struct net *net, struct super_block *sb);
> > > +#else
> > > +static inline void nfsd4_revoke_states(struct net *net, struct super_block *sb)
> > > +{
> > > +}
> > > +#endif
> > > +
> > >  /* grace period management */
> > >  void nfsd4_end_grace(struct nfsd_net *nn);
> > >  
> > > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> > > index fbc0ccb40424..e359d531402c 100644
> > > --- a/fs/nfsd/trace.h
> > > +++ b/fs/nfsd/trace.h
> > > @@ -648,6 +648,9 @@ TRACE_DEFINE_ENUM(NFS4_CLOSED_STID);
> > >  TRACE_DEFINE_ENUM(NFS4_REVOKED_DELEG_STID);
> > >  TRACE_DEFINE_ENUM(NFS4_CLOSED_DELEG_STID);
> > >  TRACE_DEFINE_ENUM(NFS4_LAYOUT_STID);
> > > +TRACE_DEFINE_ENUM(NFS4_ADMIN_REVOKED_STID);
> > > +TRACE_DEFINE_ENUM(NFS4_ADMIN_REVOKED_LOCK_STID);
> > > +TRACE_DEFINE_ENUM(NFS4_ADMIN_REVOKED_DELEG_STID);
> > >  
> > >  #define show_stid_type(x)						\
> > >  	__print_flags(x, "|",						\
> > > @@ -657,7 +660,10 @@ TRACE_DEFINE_ENUM(NFS4_LAYOUT_STID);
> > >  		{ NFS4_CLOSED_STID,		"CLOSED" },		\
> > >  		{ NFS4_REVOKED_DELEG_STID,	"REVOKED" },		\
> > >  		{ NFS4_CLOSED_DELEG_STID,	"CLOSED_DELEG" },	\
> > > -		{ NFS4_LAYOUT_STID,		"LAYOUT" })
> > > +		{ NFS4_LAYOUT_STID,		"LAYOUT" },		\
> > > +		{ NFS4_ADMIN_REVOKED_STID,	"ADMIN_REVOKED" },	\
> > > +		{ NFS4_ADMIN_REVOKED_LOCK_STID,	"ADMIN_REVOKED_LOCK" },	\
> > > +		{ NFS4_ADMIN_REVOKED_DELEG_STID,"ADMIN_REVOKED_DELEG" })
> > >  
> > >  DECLARE_EVENT_CLASS(nfsd_stid_class,
> > >  	TP_PROTO(
> > 
> > -- 
> > Jeff Layton <jlayton@kernel.org>
> > 
> 

-- 
Jeff Layton <jlayton@kernel.org>