sunrpc: add debugfs file for displaying client rpc_task queue

It's possible to get a dump of the RPC task queue by writing a value to
/proc/sys/sunrpc/rpc_debug. If you write any value to that file, you get
a dump of the RPC client task list into the log buffer. This is a rather
inconvenient interface however, and makes it hard to get immediate info
about the task queue.

Add a new directory hierarchy under debugfs:

    sunrpc/
        rpc_clnt/
            <clientid>/

Within each clientid directory we create a new "tasks" file that will
dump info similar to what shows up in the log buffer, but with a few
small differences -- we avoid printing raw kernel addresses in favor of
symbolic names and the XID is also displayed.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

2 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index 70736b98c721..d86acc63b25f 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -63,6 +63,9 @@ struct rpc_clnt {
         struct rpc_rtt          cl_rtt_default;
         struct rpc_timeout      cl_timeout_default;
         const struct rpc_program *cl_program;
+#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
+        struct dentry           *cl_debugfs;    /* debugfs directory */
+#endif
 };
 
 /*
@@ -176,5 +179,6 @@ size_t		rpc_peeraddr(struct rpc_clnt *, struct sockaddr *, size_t);
 const char      *rpc_peeraddr2str(struct rpc_clnt *, enum rpc_display_format_t);
 int             rpc_localaddr(struct rpc_clnt *, struct sockaddr *, size_t);
 
+const char *rpc_proc_name(const struct rpc_task *task);
 #endif /* __KERNEL__ */
 #endif /* _LINUX_SUNRPC_CLNT_H */
diff --git a/include/linux/sunrpc/debug.h b/include/linux/sunrpc/debug.h
index 43f38ee9668c..835339707094 100644
--- a/include/linux/sunrpc/debug.h
+++ b/include/linux/sunrpc/debug.h
@@ -53,9 +53,40 @@ extern unsigned int		nlm_debug;
 /*
  * Sysctl interface for RPC debugging
  */
+
+struct rpc_clnt;
+
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 void            rpc_register_sysctl(void);
 void            rpc_unregister_sysctl(void);
+int             sunrpc_debugfs_init(void);
+void            sunrpc_debugfs_exit(void);
+int             rpc_clnt_debugfs_register(struct rpc_clnt *);
+void            rpc_clnt_debugfs_unregister(struct rpc_clnt *);
+#else
+static inline int
+sunrpc_debugfs_init(void)
+{
+        return 0;
+}
+
+static inline void
+sunrpc_debugfs_exit(void)
+{
+        return;
+}
+
+static inline int
+rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
+{
+        return 0;
+}
+
+static inline void
+rpc_clnt_debugfs_unregister(struct rpc_clnt *clnt)
+{
+        return;
+}
 #endif
 
 #endif /* _LINUX_SUNRPC_DEBUG_H_ */