Re: [PATCH 06/13] nfsd: prepare for supporting admin-revocation of state

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2024-01-29 at 14:29 +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 a new state-id status SC_STATUS_ADMIN_REVOKED
>    which can be set on open, lock, or delegation state.
>  - 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.
>    Decrements 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/nfs4state.c | 85 ++++++++++++++++++++++++++++++++++++++++++++-
>  fs/nfsd/nfsctl.c    |  1 +
>  fs/nfsd/nfsd.h      |  1 +
>  fs/nfsd/state.h     | 10 ++++++
>  fs/nfsd/trace.h     |  3 +-
>  5 files changed, 98 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 6bccdd0af814..8db224906864 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -1210,6 +1210,8 @@ nfs4_put_stid(struct nfs4_stid *s)
>  		return;
>  	}
>  	idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
> +	if (s->sc_status & SC_STATUS_ADMIN_REVOKED)
> +		atomic_dec(&s->sc_client->cl_admin_revoked);
>  	nfs4_free_cpntf_statelist(clp->net, s);
>  	spin_unlock(&clp->cl_lock);
>  	s->sc_free(s);
> @@ -1529,6 +1531,8 @@ static void put_ol_stateid_locked(struct nfs4_ol_stateid *stp,
>  	}
>  
>  	idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
> +	if (s->sc_status & SC_STATUS_ADMIN_REVOKED)
> +		atomic_dec(&s->sc_client->cl_admin_revoked);
>  	list_add(&stp->st_locks, reaplist);
>  }
>  
> @@ -1674,6 +1678,68 @@ 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 int 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_status == 0 &&
> +		    stid->sc_file->fi_inode->i_sb == sb) {
> +			refcount_inc(&stid->sc_count);
> +			break;
> +		}
> +	spin_unlock(&clp->cl_lock);
> +	return stid;
> +}
> +
> +/**
> + * nfsd4_revoke_states - revoke all nfsv4 states associated with given filesystem
> + * @net - used to identify instance of nfsd (there is one per net namespace)
> + * @sb - super_block used to identify target filesystem
> + *
> + * All nfs4 states (open, lock, delegation, layout) held by the server instance
> + * and associated with a file on the given filesystem will be revoked resulting
> + * in any files being closed and so all references from nfsd to the filesystem
> + * being released.  Thus nfsd will no longer prevent the filesystem from being
> + * unmounted.
> + *
> + * The clients which own the states will subsequently being notified that the
> + * states have been "admin-revoked".
> + */
> +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 int 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)
>  {
> @@ -2545,6 +2611,8 @@ 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;
> @@ -4058,6 +4126,8 @@ 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);
> @@ -4546,7 +4616,9 @@ nfsd4_verify_open_stid(struct nfs4_stid *s)
>  {
>  	__be32 ret = nfs_ok;
>  
> -	if (s->sc_status & SC_STATUS_REVOKED)
> +	if (s->sc_status & SC_STATUS_ADMIN_REVOKED)
> +		ret = nfserr_admin_revoked;
> +	else if (s->sc_status & SC_STATUS_REVOKED)
>  		ret = nfserr_deleg_revoked;
>  	else if (s->sc_status & SC_STATUS_CLOSED)
>  		ret = nfserr_bad_stateid;
> @@ -5137,6 +5209,11 @@ nfs4_check_deleg(struct nfs4_client *cl, struct nfsd4_open *open,
>  	deleg = find_deleg_stateid(cl, &open->op_delegate_stateid);
>  	if (deleg == NULL)
>  		goto out;
> +	if (deleg->dl_stid.sc_status & SC_STATUS_ADMIN_REVOKED) {
> +		nfs4_put_stid(&deleg->dl_stid);
> +		status = nfserr_admin_revoked;
> +		goto out;
> +	}
>  	if (deleg->dl_stid.sc_status & SC_STATUS_REVOKED) {
>  		nfs4_put_stid(&deleg->dl_stid);
>  		status = nfserr_deleg_revoked;
> @@ -6443,6 +6520,8 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
>  		 */
>  		statusmask |= SC_STATUS_REVOKED;
>  
> +	statusmask |= SC_STATUS_ADMIN_REVOKED;
> +
>  	if (ZERO_STATEID(stateid) || ONE_STATEID(stateid) ||
>  		CLOSE_STATEID(stateid))
>  		return nfserr_bad_stateid;
> @@ -6461,6 +6540,10 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
>  		nfs4_put_stid(stid);
>  		return nfserr_deleg_revoked;
>  	}
> +	if (stid->sc_status & SC_STATUS_ADMIN_REVOKED) {
> +		nfs4_put_stid(stid);
> +		return nfserr_admin_revoked;
> +	}
>  	*s = stid;
>  	return nfs_ok;
>  }
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index f206ca32e7f5..4bae65e8d28a 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 304e9728b929..9a86fe8a39ef 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -274,6 +274,7 @@ 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 ffc8920d0558..7fa83265ad9a 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -112,6 +112,7 @@ struct nfs4_stid {
>  #define SC_STATUS_CLOSED	BIT(0)
>  /* For a deleg stateid kept around only to process free_stateid's: */
>  #define SC_STATUS_REVOKED	BIT(1)
> +#define SC_STATUS_ADMIN_REVOKED	BIT(2)
>  	unsigned short		sc_status;
>  
>  	struct list_head	sc_cp_list;
> @@ -367,6 +368,7 @@ 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;
> @@ -730,6 +732,14 @@ 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 fe08ca18b647..5c58da9f86b7 100644
> --- a/fs/nfsd/trace.h
> +++ b/fs/nfsd/trace.h
> @@ -651,7 +651,8 @@ DEFINE_STATESEQID_EVENT(open_confirm);
>  #define show_stid_status(x)						\
>  	__print_flags(x, "|",						\
>  		{ SC_STATUS_CLOSED,		"CLOSED" },		\
> -		{ SC_STATUS_REVOKED,		"REVOKED" })		\
> +		{ SC_STATUS_REVOKED,		"REVOKED" },		\
> +		{ SC_STATUS_ADMIN_REVOKED,	"ADMIN_REVOKED" })
>  
>  DECLARE_EVENT_CLASS(nfsd_stid_class,
>  	TP_PROTO(

Reviewed-by: Jeff Layton <jlayton@kernel.org>