[PATCH v6 3/3] NFSD: add rpc_status entry in nfsd debug filesystem

[Lorenzo Bianconi <lorenzo@kernel.org>]

Introduce rpc_status entry in nfsd debug filesystem in order to dump
pending RPC requests debugging information.

Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=366
Reviewed-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 fs/nfsd/nfs4proc.c         |   4 +-
 fs/nfsd/nfsctl.c           |   9 +++
 fs/nfsd/nfsd.h             |   7 ++
 fs/nfsd/nfssvc.c           | 140 +++++++++++++++++++++++++++++++++++++
 include/linux/sunrpc/svc.h |   1 +
 net/sunrpc/svc.c           |   2 +-
 6 files changed, 159 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index aa4f21f92deb..ff5a1dddc0ed 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2496,8 +2496,6 @@ static inline void nfsd4_increment_op_stats(u32 opnum)
 
 static const struct nfsd4_operation nfsd4_ops[];
 
-static const char *nfsd4_op_name(unsigned opnum);
-
 /*
  * Enforce NFSv4.1 COMPOUND ordering rules:
  *
@@ -3627,7 +3625,7 @@ void warn_on_nonidempotent_op(struct nfsd4_op *op)
 	}
 }
 
-static const char *nfsd4_op_name(unsigned opnum)
+const char *nfsd4_op_name(unsigned int opnum)
 {
 	if (opnum < ARRAY_SIZE(nfsd4_ops))
 		return nfsd4_ops[opnum].op_name;
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index dad88bff3b9e..83eb5c6d894e 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -47,6 +47,7 @@ enum {
 	NFSD_MaxBlkSize,
 	NFSD_MaxConnections,
 	NFSD_Filecache,
+	NFSD_Rpc_Status,
 	/*
 	 * The below MUST come last.  Otherwise we leave a hole in nfsd_files[]
 	 * with !CONFIG_NFSD_V4 and simple_fill_super() goes oops
@@ -195,6 +196,13 @@ static inline struct net *netns(struct file *file)
 	return file_inode(file)->i_sb->s_fs_info;
 }
 
+static const struct file_operations nfsd_rpc_status_operations = {
+	.open		= nfsd_rpc_status_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= nfsd_stats_release,
+};
+
 /*
  * write_unlock_ip - Release all locks used by a client
  *
@@ -1394,6 +1402,7 @@ static int nfsd_fill_super(struct super_block *sb, struct fs_context *fc)
 		[NFSD_MaxBlkSize] = {"max_block_size", &transaction_ops, S_IWUSR|S_IRUGO},
 		[NFSD_MaxConnections] = {"max_connections", &transaction_ops, S_IWUSR|S_IRUGO},
 		[NFSD_Filecache] = {"filecache", &nfsd_file_cache_stats_fops, S_IRUGO},
+		[NFSD_Rpc_Status] = {"rpc_status", &nfsd_rpc_status_operations, S_IRUGO},
 #ifdef CONFIG_NFSD_V4
 		[NFSD_Leasetime] = {"nfsv4leasetime", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Gracetime] = {"nfsv4gracetime", &transaction_ops, S_IWUSR|S_IRUSR},
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index 55b9d85ed71b..3e8a47b93fd4 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -94,6 +94,7 @@ int		nfsd_get_nrthreads(int n, int *, struct net *);
 int		nfsd_set_nrthreads(int n, int *, struct net *);
 int		nfsd_pool_stats_open(struct inode *, struct file *);
 int		nfsd_stats_release(struct inode *, struct file *);
+int		nfsd_rpc_status_open(struct inode *inode, struct file *file);
 void		nfsd_shutdown_threads(struct net *net);
 
 static inline void nfsd_put(struct net *net)
@@ -511,12 +512,18 @@ extern void nfsd4_ssc_init_umount_work(struct nfsd_net *nn);
 
 extern void nfsd4_init_leases_net(struct nfsd_net *nn);
 
+const char *nfsd4_op_name(unsigned int opnum);
 #else /* CONFIG_NFSD_V4 */
 static inline int nfsd4_is_junction(struct dentry *dentry)
 {
 	return 0;
 }
 
+static inline const char *nfsd4_op_name(unsigned int opnum)
+{
+	return "unknown_operation";
+}
+
 static inline void nfsd4_init_leases_net(struct nfsd_net *nn) { };
 
 #define register_cld_notifier() 0
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 460219030ce1..237be14d3a11 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -998,6 +998,15 @@ 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:
@@ -1015,6 +1024,12 @@ 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;
@@ -1101,3 +1116,128 @@ int nfsd_stats_release(struct inode *inode, struct file *file)
 	mutex_unlock(&nfsd_mutex);
 	return ret;
 }
+
+static int nfsd_rpc_status_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = file_inode(m->file);
+	struct nfsd_net *nn = net_generic(inode->i_sb->s_fs_info, nfsd_net_id);
+	int i;
+
+	seq_puts(m, "# XID FLAGS VERS PROC TIMESTAMP SADDR SPORT DADDR DPORT COMPOUND_OPS\n");
+
+	rcu_read_lock();
+
+	for (i = 0; i < nn->nfsd_serv->sv_nrpools; i++) {
+		struct svc_rqst *rqstp;
+
+		list_for_each_entry_rcu(rqstp,
+				&nn->nfsd_serv->sv_pools[i].sp_all_threads,
+				rq_all) {
+			struct {
+				struct sockaddr daddr;
+				struct sockaddr saddr;
+				unsigned long rq_flags;
+				const char *pc_name;
+				ktime_t rq_stime;
+				__be32 rq_xid;
+				u32 rq_vers;
+				/* NFSv4 compund */
+				u32 opnum[NFSD_MAX_OPS_PER_COMPOUND];
+			} rqstp_info;
+			unsigned int status_counter;
+			char buf[RPC_MAX_ADDRBUFLEN];
+			int opcnt = 0;
+
+			/*
+			 * 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;
+
+			rqstp_info.rq_xid = rqstp->rq_xid;
+			rqstp_info.rq_flags = rqstp->rq_flags;
+			rqstp_info.rq_vers = rqstp->rq_vers;
+			rqstp_info.pc_name = svc_proc_name(rqstp);
+			rqstp_info.rq_stime = rqstp->rq_stime;
+			memcpy(&rqstp_info.daddr, svc_daddr(rqstp),
+			       sizeof(struct sockaddr));
+			memcpy(&rqstp_info.saddr, svc_addr(rqstp),
+			       sizeof(struct sockaddr));
+
+#ifdef CONFIG_NFSD_V4
+			if (rqstp->rq_vers == NFS4_VERSION &&
+			    rqstp->rq_proc == NFSPROC4_COMPOUND) {
+				/* NFSv4 compund */
+				struct nfsd4_compoundargs *args = rqstp->rq_argp;
+				int j;
+
+				opcnt = args->opcnt;
+				for (j = 0; j < opcnt; j++) {
+					struct nfsd4_op *op = &args->ops[j];
+
+					rqstp_info.opnum[j] = op->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;
+
+			seq_printf(m,
+				   "%04u %04ld NFSv%d %s %016lld",
+				   be32_to_cpu(rqstp_info.rq_xid),
+				   rqstp_info.rq_flags,
+				   rqstp_info.rq_vers,
+				   rqstp_info.pc_name,
+				   ktime_to_us(rqstp_info.rq_stime));
+			seq_printf(m, " %s",
+				   __svc_print_addr(&rqstp_info.saddr, buf,
+						    sizeof(buf), false));
+			seq_printf(m, " %s",
+				   __svc_print_addr(&rqstp_info.daddr, buf,
+						    sizeof(buf), false));
+			if (opcnt) {
+				int j;
+
+				seq_puts(m, " ");
+				for (j = 0; j < opcnt; j++)
+					seq_printf(m, "%s%s",
+						   nfsd4_op_name(rqstp_info.opnum[j]),
+						   j == opcnt - 1 ? "" : ":");
+			} else {
+				seq_puts(m, " -");
+			}
+			seq_puts(m, "\n");
+		}
+	}
+
+	rcu_read_unlock();
+
+	return 0;
+}
+
+/**
+ * nfsd_rpc_status_open - open routine for nfsd_rpc_status handler
+ * @inode: entry inode pointer.
+ * @file: entry file pointer.
+ *
+ * nfsd_rpc_status_open is the open routine for nfsd_rpc_status procfs handler.
+ * nfsd_rpc_status dumps pending RPC requests info queued into nfs server.
+ */
+int nfsd_rpc_status_open(struct inode *inode, struct file *file)
+{
+	int ret = nfsd_stats_open(inode);
+
+	if (ret)
+		return ret;
+
+	return single_open(file, nfsd_rpc_status_show, inode->i_private);
+}
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 7838b37bcfa8..b49c0470b4fe 100644
--- a/include/linux/sunrpc/svc.h
+++ b/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 */
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index af692bff44ab..83bee19df104 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1656,7 +1656,7 @@ const char *svc_proc_name(const struct svc_rqst *rqstp)
 		return rqstp->rq_procinfo->pc_name;
 	return "unknown";
 }
-
+EXPORT_SYMBOL_GPL(svc_proc_name);
 
 /**
  * svc_encode_result_payload - mark a range of bytes as a result payload
-- 
2.41.0