NFSD: add rpc_status netlink support

Introduce rpc_status netlink support for NFSD in order to dump pending
RPC requests debugging information from userspace.

Closes: https://bugzilla.linux-nfs.org/show_bug.cgi?id=366
Tested-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsctl.c

@@ -1496,19 +1496,200 @@ static int create_proc_exports_entry(void)
 
 unsigned int nfsd_net_id;
 
+/**
+ * nfsd_nl_rpc_status_get_start - Prepare rpc_status_get dumpit
+ * @cb: netlink metadata and command arguments
+ *
+ * Return values:
+ *   %0: The rpc_status_get command may proceed
+ *   %-ENODEV: There is no NFSD running in this namespace
+ */
 int nfsd_nl_rpc_status_get_start(struct netlink_callback *cb)
 {
+	struct nfsd_net *nn = net_generic(sock_net(cb->skb->sk), nfsd_net_id);
+	int ret = -ENODEV;
+
+	mutex_lock(&nfsd_mutex);
+	if (nn->nfsd_serv) {
+		svc_get(nn->nfsd_serv);
+		ret = 0;
+	}
+	mutex_unlock(&nfsd_mutex);
+
+	return ret;
+}
+
+static int nfsd_genl_rpc_status_compose_msg(struct sk_buff *skb,
+					    struct netlink_callback *cb,
+					    struct nfsd_genl_rqstp *rqstp)
+{
+	void *hdr;
+	u32 i;
+
+	hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
+			  &nfsd_nl_family, 0, NFSD_CMD_RPC_STATUS_GET);
+	if (!hdr)
+		return -ENOBUFS;
+
+	if (nla_put_be32(skb, NFSD_A_RPC_STATUS_XID, rqstp->rq_xid) ||
+	    nla_put_u32(skb, NFSD_A_RPC_STATUS_FLAGS, rqstp->rq_flags) ||
+	    nla_put_u32(skb, NFSD_A_RPC_STATUS_PROG, rqstp->rq_prog) ||
+	    nla_put_u32(skb, NFSD_A_RPC_STATUS_PROC, rqstp->rq_proc) ||
+	    nla_put_u8(skb, NFSD_A_RPC_STATUS_VERSION, rqstp->rq_vers) ||
+	    nla_put_s64(skb, NFSD_A_RPC_STATUS_SERVICE_TIME,
+			ktime_to_us(rqstp->rq_stime),
+			NFSD_A_RPC_STATUS_PAD))
+		return -ENOBUFS;
+
+	switch (rqstp->rq_saddr.sa_family) {
+	case AF_INET: {
+		const struct sockaddr_in *s_in, *d_in;
+
+		s_in = (const struct sockaddr_in *)&rqstp->rq_saddr;
+		d_in = (const struct sockaddr_in *)&rqstp->rq_daddr;
+		if (nla_put_in_addr(skb, NFSD_A_RPC_STATUS_SADDR4,
+				    s_in->sin_addr.s_addr) ||
+		    nla_put_in_addr(skb, NFSD_A_RPC_STATUS_DADDR4,
+				    d_in->sin_addr.s_addr) ||
+		    nla_put_be16(skb, NFSD_A_RPC_STATUS_SPORT,
+				 s_in->sin_port) ||
+		    nla_put_be16(skb, NFSD_A_RPC_STATUS_DPORT,
+				 d_in->sin_port))
+			return -ENOBUFS;
+		break;
+	}
+	case AF_INET6: {
+		const struct sockaddr_in6 *s_in, *d_in;
+
+		s_in = (const struct sockaddr_in6 *)&rqstp->rq_saddr;
+		d_in = (const struct sockaddr_in6 *)&rqstp->rq_daddr;
+		if (nla_put_in6_addr(skb, NFSD_A_RPC_STATUS_SADDR6,
+				     &s_in->sin6_addr) ||
+		    nla_put_in6_addr(skb, NFSD_A_RPC_STATUS_DADDR6,
+				     &d_in->sin6_addr) ||
+		    nla_put_be16(skb, NFSD_A_RPC_STATUS_SPORT,
+				 s_in->sin6_port) ||
+		    nla_put_be16(skb, NFSD_A_RPC_STATUS_DPORT,
+				 d_in->sin6_port))
+			return -ENOBUFS;
+		break;
+	}
+	}
+
+	for (i = 0; i < rqstp->rq_opcnt; i++)
+		if (nla_put_u32(skb, NFSD_A_RPC_STATUS_COMPOUND_OPS,
+				rqstp->rq_opnum[i]))
+			return -ENOBUFS;
+
+	genlmsg_end(skb, hdr);
 	return 0;
 }
 
+/**
+ * nfsd_nl_rpc_status_get_dumpit - Handle rpc_status_get dumpit
+ * @skb: reply buffer
+ * @cb: netlink metadata and command arguments
+ *
+ * Returns the size of the reply or a negative errno.
+ */
 int nfsd_nl_rpc_status_get_dumpit(struct sk_buff *skb,
 				  struct netlink_callback *cb)
 {
-	return 0;
+	struct nfsd_net *nn = net_generic(sock_net(skb->sk), nfsd_net_id);
+	int i, ret, rqstp_index = 0;
+
+	rcu_read_lock();
+
+	for (i = 0; i < nn->nfsd_serv->sv_nrpools; i++) {
+		struct svc_rqst *rqstp;
+
+		if (i < cb->args[0]) /* already consumed */
+			continue;
+
+		rqstp_index = 0;
+		list_for_each_entry_rcu(rqstp,
+				&nn->nfsd_serv->sv_pools[i].sp_all_threads,
+				rq_all) {
+			struct nfsd_genl_rqstp genl_rqstp;
+			unsigned int status_counter;
+
+			if (rqstp_index++ < cb->args[1]) /* already consumed */
+				continue;
+			/*
+			 * Acquire rq_status_counter before parsing the rqst
+			 * fields. rq_status_counter is set to an odd value in
+			 * order to notify the consumers the rqstp fields are
+			 * meaningful.
+			 */
+			status_counter =
+				smp_load_acquire(&rqstp->rq_status_counter);
+			if (!(status_counter & 1))
+				continue;
+
+			genl_rqstp.rq_xid = rqstp->rq_xid;
+			genl_rqstp.rq_flags = rqstp->rq_flags;
+			genl_rqstp.rq_vers = rqstp->rq_vers;
+			genl_rqstp.rq_prog = rqstp->rq_prog;
+			genl_rqstp.rq_proc = rqstp->rq_proc;
+			genl_rqstp.rq_stime = rqstp->rq_stime;
+			genl_rqstp.rq_opcnt = 0;
+			memcpy(&genl_rqstp.rq_daddr, svc_daddr(rqstp),
+			       sizeof(struct sockaddr));
+			memcpy(&genl_rqstp.rq_saddr, svc_addr(rqstp),
+			       sizeof(struct sockaddr));
+
+#ifdef CONFIG_NFSD_V4
+			if (rqstp->rq_vers == NFS4_VERSION &&
+			    rqstp->rq_proc == NFSPROC4_COMPOUND) {
+				/* NFSv4 compound */
+				struct nfsd4_compoundargs *args;
+				int j;
+
+				args = rqstp->rq_argp;
+				genl_rqstp.rq_opcnt = args->opcnt;
+				for (j = 0; j < genl_rqstp.rq_opcnt; j++)
+					genl_rqstp.rq_opnum[j] =
+						args->ops[j].opnum;
+			}
+#endif /* CONFIG_NFSD_V4 */
+
+			/*
+			 * Acquire rq_status_counter before reporting the rqst
+			 * fields to the user.
+			 */
+			if (smp_load_acquire(&rqstp->rq_status_counter) !=
+			    status_counter)
+				continue;
+
+			ret = nfsd_genl_rpc_status_compose_msg(skb, cb,
+							       &genl_rqstp);
+			if (ret)
+				goto out;
+		}
+	}
+
+	cb->args[0] = i;
+	cb->args[1] = rqstp_index;
+	ret = skb->len;
+out:
+	rcu_read_unlock();
+
+	return ret;
 }
 
+/**
+ * nfsd_nl_rpc_status_get_done - rpc_status_get dumpit post-processing
+ * @cb: netlink metadata and command arguments
+ *
+ * Return values:
+ *   %0: Success
+ */
 int nfsd_nl_rpc_status_get_done(struct netlink_callback *cb)
 {
+	mutex_lock(&nfsd_mutex);
+	nfsd_put(sock_net(cb->skb->sk));
+	mutex_unlock(&nfsd_mutex);
+
 	return 0;
 }
 
@@ -1606,6 +1787,10 @@ static int __init init_nfsd(void)
 	retval = register_filesystem(&nfsd_fs_type);
 	if (retval)
 		goto out_free_all;
+	retval = genl_register_family(&nfsd_nl_family);
+	if (retval)
+		goto out_free_all;
+
 	return 0;
 out_free_all:
 	nfsd4_destroy_laundry_wq();
@@ -1630,6 +1815,7 @@ static int __init init_nfsd(void)
 
 static void __exit exit_nfsd(void)
 {
+	genl_unregister_family(&nfsd_nl_family);
 	unregister_filesystem(&nfsd_fs_type);
 	nfsd4_destroy_laundry_wq();
 	unregister_cld_notifier();

fs/nfsd/nfsd.h

@@ -62,6 +62,23 @@ struct readdir_cd {
 	__be32			err;	/* 0, nfserr, or nfserr_eof */
 };
 
+/* Maximum number of operations per session compound */
+#define NFSD_MAX_OPS_PER_COMPOUND	50
+
+struct nfsd_genl_rqstp {
+	struct sockaddr		rq_daddr;
+	struct sockaddr		rq_saddr;
+	unsigned long		rq_flags;
+	ktime_t			rq_stime;
+	__be32			rq_xid;
+	u32			rq_vers;
+	u32			rq_prog;
+	u32			rq_proc;
+
+	/* NFSv4 compound */
+	u32			rq_opcnt;
+	u32			rq_opnum[NFSD_MAX_OPS_PER_COMPOUND];
+};
 
 extern struct svc_program	nfsd_program;
 extern const struct svc_version	nfsd_version2, nfsd_version3, nfsd_version4;

fs/nfsd/nfssvc.c

@@ -997,6 +997,15 @@ int nfsd_dispatch(struct svc_rqst *rqstp)
 	if (!proc->pc_decode(rqstp, &rqstp->rq_arg_stream))
 		goto out_decode_err;
 
+	/*
+	 * Release rq_status_counter setting it to an odd value after the rpc
+	 * request has been properly parsed. rq_status_counter is used to
+	 * notify the consumers if the rqstp fields are stable
+	 * (rq_status_counter is odd) or not meaningful (rq_status_counter
+	 * is even).
+	 */
+	smp_store_release(&rqstp->rq_status_counter, rqstp->rq_status_counter | 1);
+
 	rp = NULL;
 	switch (nfsd_cache_lookup(rqstp, &rp)) {
 	case RC_DOIT:
@@ -1014,6 +1023,12 @@ int nfsd_dispatch(struct svc_rqst *rqstp)
 	if (!proc->pc_encode(rqstp, &rqstp->rq_res_stream))
 		goto out_encode_err;
 
+	/*
+	 * Release rq_status_counter setting it to an even value after the rpc
+	 * request has been properly processed.
+	 */
+	smp_store_release(&rqstp->rq_status_counter, rqstp->rq_status_counter + 1);
+
 	nfsd_cache_update(rqstp, rp, rqstp->rq_cachetype, statp + 1);
 out_cached_reply:
 	return 1;

fs/nfsd/state.h

@@ -195,8 +195,6 @@ static inline struct nfs4_delegation *delegstateid(struct nfs4_stid *s)
 
 /* Maximum number of slots per session. 160 is useful for long haul TCP */
 #define NFSD_MAX_SLOTS_PER_SESSION     160
-/* Maximum number of operations per session compound */
-#define NFSD_MAX_OPS_PER_COMPOUND	50
 /* Maximum  session per slot cache size */
 #define NFSD_SLOT_CACHE_SIZE		2048
 /* Maximum number of NFSD_SLOT_CACHE_SIZE slots per session */

include/linux/sunrpc/svc.h

@@ -251,6 +251,7 @@ struct svc_rqst {
 						 * net namespace
 						 */
 	void **			rq_lease_breaker; /* The v4 client breaking a lease */
+	unsigned int		rq_status_counter; /* RPC processing counter */
 };
 
 /* bits for rq_flags */