linux-kernel - [PATCH v4 04/18] nfsd: add a tracepoint to nfsd_lookup

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Message-ID: <20250503195936.5083-5-cel@kernel.org>
Date: Sat,  3 May 2025 15:59:22 -0400
From: cel@...nel.org
To: NeilBrown <neil@...wn.name>,
	Jeff Layton <jlayton@...nel.org>,
	Olga Kornievskaia <okorniev@...hat.com>,
	Dai Ngo <dai.ngo@...cle.com>,
	Tom Talpey <tom@...pey.com>,
	Trond Myklebust <trond.myklebust@...merspace.com>,
	Anna Schumaker <anna@...nel.org>
Cc: sargun@...gun.me,
	<linux-nfs@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH v4 04/18] nfsd: add a tracepoint to nfsd_lookup_dentry

From: Jeff Layton <jlayton@...nel.org>

Replace the dprintk in nfsd_lookup_dentry() with a trace point.
nfsd_lookup_dentry() is called frequently enough that enabling this
dprintk call site would result in log floods and performance issues.

Signed-off-by: Jeff Layton <jlayton@...nel.org>
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
---
 fs/nfsd/trace.h | 23 +++++++++++++++++++++++
 fs/nfsd/vfs.c   |  2 +-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
index b435276a1aaa..661a870d62f5 100644
--- a/fs/nfsd/trace.h
+++ b/fs/nfsd/trace.h
@@ -2394,6 +2394,29 @@ TRACE_EVENT(nfsd_vfs_setattr,
 	)
 )
 
+TRACE_EVENT(nfsd_vfs_lookup,
+	TP_PROTO(
+		const struct svc_rqst *rqstp,
+		const struct svc_fh *fhp,
+		const char *name,
+		unsigned int len
+	),
+	TP_ARGS(rqstp, fhp, name, len),
+	TP_STRUCT__entry(
+		NFSD_TRACE_PROC_CALL_FIELDS(rqstp)
+		__field(u32, fh_hash)
+		__string_len(name, name, len)
+	),
+	TP_fast_assign(
+		NFSD_TRACE_PROC_CALL_ASSIGNMENTS(rqstp);
+		__entry->fh_hash = knfsd_fh_hash(&fhp->fh_handle);
+		__assign_str(name);
+	),
+	TP_printk("xid=0x%08x fh_hash=0x%08x name=%s",
+		__entry->xid, __entry->fh_hash, __get_str(name)
+	)
+);
+
 #endif /* _NFSD_TRACE_H */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 9e0a858d2129..657ba0c2da14 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -246,7 +246,7 @@ nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	struct dentry		*dentry;
 	int			host_err;
 
-	dprintk("nfsd: nfsd_lookup(fh %s, %.*s)\n", SVCFH_fmt(fhp), len,name);
+	trace_nfsd_vfs_lookup(rqstp, fhp, name, len);
 
 	dparent = fhp->fh_dentry;
 	exp = exp_get(fhp->fh_export);
-- 
2.49.0