nfsd: add tracepoint to nfsd_readdir

Observe the start of NFS READDIR operations.

The NFS READDIR's count argument can be interesting when tuning a
client's readdir behavior.

However, the count argument is not passed to nfsd_readdir(). To
properly capture the count argument, this tracepoint must appear in
each proc function before the nfsd_readdir() call.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: jtlayton

fs/nfsd/nfs3proc.c

@@ -625,6 +625,7 @@ nfsd3_proc_readdir(struct svc_rqst *rqstp)
 	dprintk("nfsd: READDIR(3)  %s %d bytes at %d\n",
 				SVCFH_fmt(&argp->fh),
 				argp->count, (u32) argp->cookie);
+	trace_nfsd_vfs_readdir(rqstp, &argp->fh, argp->count, argp->cookie);
 
 	nfsd3_init_dirlist_pages(rqstp, resp, argp->count);
 
@@ -659,6 +660,7 @@ nfsd3_proc_readdirplus(struct svc_rqst *rqstp)
 	dprintk("nfsd: READDIR+(3) %s %d bytes at %d\n",
 				SVCFH_fmt(&argp->fh),
 				argp->count, (u32) argp->cookie);
+	trace_nfsd_vfs_readdir(rqstp, &argp->fh, argp->count, argp->cookie);
 
 	nfsd3_init_dirlist_pages(rqstp, resp, argp->count);
 

fs/nfsd/nfs4proc.c

@@ -998,6 +998,9 @@ nfsd4_readdir(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	u64 cookie = readdir->rd_cookie;
 	static const nfs4_verifier zeroverf;
 
+	trace_nfsd_vfs_readdir(rqstp, &cstate->current_fh,
+			       readdir->rd_maxcount, readdir->rd_cookie);
+
 	/* no need to check permission - this will be done in nfsd_readdir() */
 
 	if (readdir->rd_bmval[1] & NFSD_WRITEONLY_ATTRS_WORD1)

fs/nfsd/nfsproc.c

@@ -10,6 +10,7 @@
 #include "cache.h"
 #include "xdr.h"
 #include "vfs.h"
+#include "trace.h"
 
 #define NFSDDBG_FACILITY		NFSDDBG_PROC
 
@@ -618,6 +619,7 @@ nfsd_proc_readdir(struct svc_rqst *rqstp)
 	dprintk("nfsd: READDIR  %s %d bytes at %d\n",
 		SVCFH_fmt(&argp->fh),		
 		argp->count, argp->cookie);
+	trace_nfsd_vfs_readdir(rqstp, &argp->fh, argp->count, argp->cookie);
 
 	nfsd_init_dirlist_pages(rqstp, resp, argp->count);
 

fs/nfsd/trace.h

@@ -2553,6 +2553,32 @@ TRACE_EVENT(nfsd_vfs_rename,
 	)
 );
 
+TRACE_EVENT(nfsd_vfs_readdir,
+	TP_PROTO(
+		const struct svc_rqst *rqstp,
+		const struct svc_fh *fhp,
+		u32 count,
+		u64 offset
+	),
+	TP_ARGS(rqstp, fhp, count, offset),
+	TP_STRUCT__entry(
+		NFSD_TRACE_PROC_CALL_FIELDS(rqstp)
+		__field(u32, fh_hash)
+		__field(u32, count)
+		__field(u64, offset)
+	),
+	TP_fast_assign(
+		NFSD_TRACE_PROC_CALL_ASSIGNMENTS(rqstp);
+		__entry->fh_hash = knfsd_fh_hash(&fhp->fh_handle);
+		__entry->count = count;
+		__entry->offset = offset;
+	),
+	TP_printk("xid=0x%08x fh_hash=0x%08x offset=%llu count=%u",
+		__entry->xid, __entry->fh_hash,
+		__entry->offset, __entry->count
+	)
+);
+
 #endif /* _NFSD_TRACE_H */
 
 #undef TRACE_INCLUDE_PATH