Add dtnfsclient, a first cut at an NFSv2/v3 client reuest DTrace

provider.  The NFS client exposes 'start' and 'done' probes for NFSv2
and NFSv3 RPCs when using the new RPC implementation, passing in the
vnode, mbuf chain, credential, and NFSv2 or NFSv3 procedure number.
For 'done' probes, the error number is also available.

Probes are named in the following way:

  ...
  nfsclient:nfs2:write:start
  nfsclient:nfs2:write:done
  ...
  nfsclient:nfs3:access:start
  nfsclient:nfs3:access:done
  ...

Access to the unmarshalled arguments is not easily available at this
point in the stack, but the passed probe arguments are sufficient to
to a lot of interesting things in practice.  Technically, these probes
may cover multiple RPC retransmits, and even transactions if the
transaction ID change as a result of authentication failure or a
jukebox error from the server, but usefully capture the intent of a
single NFS request, such as access, getattr, write, etc.

Typical use might involve profiling RPC latency by system call, number
of RPCs, how often a getattr leads to a call to access, when failed
access control checks occur, etc.  More detailed RPC information might
best be provided by adding a krpc provider.  It would also be useful
to add NFS client probes for events such as the access cache or
attribute cache satisfying requests without an RPC.

Sponsored by:	Google, Inc.
MFC after:	1 month

1 files changed, 75 insertions, 0 deletions

diff --git a/sys/nfsclient/nfs_krpc.c b/sys/nfsclient/nfs_krpc.c
index ce6a87b..8f3f124 100644
--- a/sys/nfsclient/nfs_krpc.c
+++ b/sys/nfsclient/nfs_krpc.c
@@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
  */
 
 #include "opt_inet6.h"
+#include "opt_kdtrace.h"
 #include "opt_kgssapi.h"
 
 #include <sys/param.h>
@@ -73,6 +74,25 @@ __FBSDID("$FreeBSD$");
 
 #ifndef NFS_LEGACYRPC
 
+#ifdef KDTRACE_HOOKS
+#include <sys/dtrace_bsd.h>
+
+dtrace_nfsclient_nfs23_start_probe_func_t
+    dtrace_nfsclient_nfs23_start_probe;
+
+dtrace_nfsclient_nfs23_done_probe_func_t
+    dtrace_nfsclient_nfs23_done_probe;
+
+/*
+ * Registered probes by RPC type.
+ */
+uint32_t	nfsclient_nfs2_start_probes[NFS_NPROCS];
+uint32_t	nfsclient_nfs2_done_probes[NFS_NPROCS];
+
+uint32_t	nfsclient_nfs3_start_probes[NFS_NPROCS];
+uint32_t	nfsclient_nfs3_done_probes[NFS_NPROCS];
+#endif
+
 static int	nfs_realign_test;
 static int	nfs_realign_count;
 static int	nfs_bufpackets = 4;
@@ -468,6 +488,25 @@ nfs_request(struct vnode *vp, struct mbuf *mreq, int procnum,
 		ext.rc_timers = NULL;
 	}
 
+#ifdef KDTRACE_HOOKS
+	if (dtrace_nfsclient_nfs23_start_probe != NULL) {
+		uint32_t probe_id;
+		int probe_procnum;
+
+		if (nmp->nm_flag & NFSMNT_NFSV3) {
+			probe_id = nfsclient_nfs3_start_probes[procnum];
+			probe_procnum = procnum;
+		} else {
+			probe_id = nfsclient_nfs2_start_probes[procnum];
+			probe_procnum = (nmp->nm_flag & NFSMNT_NFSV3) ?
+			    procnum : nfsv2_procid[procnum];
+		}
+		if (probe_id != 0)
+			(dtrace_nfsclient_nfs23_start_probe)(probe_id, vp,
+			    mreq, cred, probe_procnum);
+	}
+#endif
+
 	nfsstats.rpcrequests++;
 tryagain:
 	timo.tv_sec = nmp->nm_timeo / NFS_HZ;
@@ -535,6 +574,24 @@ tryagain:
 		goto nfsmout;
 	}
 
+#ifdef KDTRACE_HOOKS
+	if (dtrace_nfsclient_nfs23_done_probe != NULL) {
+		uint32_t probe_id;
+		int probe_procnum;
+
+		if (nmp->nm_flag & NFSMNT_NFSV3) {
+			probe_id = nfsclient_nfs3_done_probes[procnum];
+			probe_procnum = procnum;
+		} else {
+			probe_id = nfsclient_nfs2_done_probes[procnum];
+			probe_procnum = (nmp->nm_flag & NFSMNT_NFSV3) ?
+			    procnum : nfsv2_procid[procnum];
+		}
+		if (probe_id != 0)
+			(dtrace_nfsclient_nfs23_done_probe)(probe_id, vp,
+			    mreq, cred, probe_procnum, 0);
+	}
+#endif
 	m_freem(mreq);
 	*mrp = mrep;
 	*mdp = md;
@@ -543,6 +600,24 @@ tryagain:
 	return (0);
 
 nfsmout:
+#ifdef KDTRACE_HOOKS
+	if (dtrace_nfsclient_nfs23_done_probe != NULL) {
+		uint32_t probe_id;
+		int probe_procnum;
+
+		if (nmp->nm_flag & NFSMNT_NFSV3) {
+			probe_id = nfsclient_nfs3_done_probes[procnum];
+			probe_procnum = procnum;
+		} else {
+			probe_id = nfsclient_nfs2_done_probes[procnum];
+			probe_procnum = (nmp->nm_flag & NFSMNT_NFSV3) ?
+			    procnum : nfsv2_procid[procnum];
+		}
+		if (probe_id != 0)
+			(dtrace_nfsclient_nfs23_done_probe)(probe_id, vp,
+			    mreq, cred, probe_procnum, error);
+	}
+#endif
 	m_freem(mreq);
 	if (auth)
 		AUTH_DESTROY(auth);