nfsd: Add I/O trace points in the NFSv4 read proc

NFSv4 read compound processing invokes nfsd_splice_read and
nfs_readv directly, so the trace points currently in nfsd_read are
not invoked for NFSv4 reads.

Move the NFSD READ trace points to common helpers so that NFSv4
reads are captured.

Also, record any local I/O error that occurs, the total count of
bytes that were actually returned, and whether splice or vectored
read was used.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4proc.c

@@ -751,6 +751,9 @@ nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	if (read->rd_offset >= OFFSET_MAX)
 		return nfserr_inval;
 
+	trace_nfsd_read_start(rqstp, &cstate->current_fh,
+			      read->rd_offset, read->rd_length);
+
 	/*
 	 * If we do a zero copy read, then a client will see read data
 	 * that reflects the state of the file *after* performing the
@@ -783,6 +786,8 @@ nfsd4_read_release(union nfsd4_op_u *u)
 {
 	if (u->read.rd_filp)
 		fput(u->read.rd_filp);
+	trace_nfsd_read_done(u->read.rd_rqstp, u->read.rd_fhp,
+			     u->read.rd_offset, u->read.rd_length);
 }
 
 static __be32

fs/nfsd/nfs4xdr.c

@@ -3427,8 +3427,9 @@ static __be32 nfsd4_encode_splice_read(
 		return nfserr_resource;
 
 	len = maxcount;
-	nfserr = nfsd_splice_read(read->rd_rqstp, file,
-				  read->rd_offset, &maxcount);
+	nfserr = nfsd_splice_read(read->rd_rqstp, read->rd_fhp,
+				  file, read->rd_offset, &maxcount);
+	read->rd_length = maxcount;
 	if (nfserr) {
 		/*
 		 * nfsd_splice_actor may have already messed with the
@@ -3511,8 +3512,9 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 	read->rd_vlen = v;
 
 	len = maxcount;
-	nfserr = nfsd_readv(file, read->rd_offset, resp->rqstp->rq_vec,
-			read->rd_vlen, &maxcount);
+	nfserr = nfsd_readv(resp->rqstp, read->rd_fhp, file, read->rd_offset,
+			    resp->rqstp->rq_vec, read->rd_vlen, &maxcount);
+	read->rd_length = maxcount;
 	if (nfserr)
 		return nfserr;
 	xdr_truncate_encode(xdr, starting_len + 8 + ((maxcount+3)&~3));

fs/nfsd/trace.h

@@ -43,7 +43,8 @@ DEFINE_EVENT(nfsd_io_class, nfsd_##name,	\
 	TP_ARGS(rqstp, fhp, offset, len))
 
 DEFINE_NFSD_IO_EVENT(read_start);
-DEFINE_NFSD_IO_EVENT(read_opened);
+DEFINE_NFSD_IO_EVENT(read_splice);
+DEFINE_NFSD_IO_EVENT(read_vector);
 DEFINE_NFSD_IO_EVENT(read_io_done);
 DEFINE_NFSD_IO_EVENT(read_done);
 DEFINE_NFSD_IO_EVENT(write_start);
@@ -82,6 +83,7 @@ DEFINE_EVENT(nfsd_err_class, nfsd_##name,	\
 		 int		len),		\
 	TP_ARGS(rqstp, fhp, offset, len))
 
+DEFINE_NFSD_ERR_EVENT(read_err);
 DEFINE_NFSD_ERR_EVENT(write_err);
 
 #include "state.h"

fs/nfsd/vfs.c

@@ -881,20 +881,24 @@ static int nfsd_direct_splice_actor(struct pipe_inode_info *pipe,
 	return __splice_from_pipe(pipe, sd, nfsd_splice_actor);
 }
 
-static __be32
-nfsd_finish_read(struct file *file, unsigned long *count, int host_err)
+static __be32 nfsd_finish_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
+			       struct file *file, loff_t offset,
+			       unsigned long *count, int host_err)
 {
 	if (host_err >= 0) {
 		nfsdstats.io_read += host_err;
 		*count = host_err;
 		fsnotify_access(file);
+		trace_nfsd_read_io_done(rqstp, fhp, offset, *count);
 		return 0;
-	} else 
+	} else {
+		trace_nfsd_read_err(rqstp, fhp, offset, host_err);
 		return nfserrno(host_err);
+	}
 }
 
-__be32 nfsd_splice_read(struct svc_rqst *rqstp,
-		     struct file *file, loff_t offset, unsigned long *count)
+__be32 nfsd_splice_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
+			struct file *file, loff_t offset, unsigned long *count)
 {
 	struct splice_desc sd = {
 		.len		= 0,
@@ -904,21 +908,23 @@ __be32 nfsd_splice_read(struct svc_rqst *rqstp,
 	};
 	int host_err;
 
+	trace_nfsd_read_splice(rqstp, fhp, offset, *count);
 	rqstp->rq_next_page = rqstp->rq_respages + 1;
 	host_err = splice_direct_to_actor(file, &sd, nfsd_direct_splice_actor);
-	return nfsd_finish_read(file, count, host_err);
+	return nfsd_finish_read(rqstp, fhp, file, offset, count, host_err);
 }
 
-__be32 nfsd_readv(struct file *file, loff_t offset, struct kvec *vec, int vlen,
-		unsigned long *count)
+__be32 nfsd_readv(struct svc_rqst *rqstp, struct svc_fh *fhp,
+		  struct file *file, loff_t offset,
+		  struct kvec *vec, int vlen, unsigned long *count)
 {
 	struct iov_iter iter;
 	int host_err;
 
+	trace_nfsd_read_vector(rqstp, fhp, offset, *count);
 	iov_iter_kvec(&iter, READ | ITER_KVEC, vec, vlen, *count);
 	host_err = vfs_iter_read(file, &iter, &offset, 0);
-
-	return nfsd_finish_read(file, count, host_err);
+	return nfsd_finish_read(rqstp, fhp, file, offset, count, host_err);
 }
 
 /*
@@ -1034,14 +1040,10 @@ __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
 
 	ra = nfsd_init_raparms(file);
 
-	trace_nfsd_read_opened(rqstp, fhp, offset, *count);
-
 	if (file->f_op->splice_read && test_bit(RQ_SPLICE_OK, &rqstp->rq_flags))
-		err = nfsd_splice_read(rqstp, file, offset, count);
+		err = nfsd_splice_read(rqstp, fhp, file, offset, count);
 	else
-		err = nfsd_readv(file, offset, vec, vlen, count);
-
-	trace_nfsd_read_io_done(rqstp, fhp, offset, *count);
+		err = nfsd_readv(rqstp, fhp, file, offset, vec, vlen, count);
 
 	if (ra)
 		nfsd_put_raparams(file, ra);

fs/nfsd/vfs.h

@@ -78,10 +78,13 @@ __be32		nfsd_commit(struct svc_rqst *, struct svc_fh *,
 __be32		nfsd_open(struct svc_rqst *, struct svc_fh *, umode_t,
 				int, struct file **);
 struct raparms;
-__be32		nfsd_splice_read(struct svc_rqst *,
-				struct file *, loff_t, unsigned long *);
-__be32		nfsd_readv(struct file *, loff_t, struct kvec *, int,
-				unsigned long *);
+__be32		nfsd_splice_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
+				struct file *file, loff_t offset,
+				unsigned long *count);
+__be32		nfsd_readv(struct svc_rqst *rqstp, struct svc_fh *fhp,
+				struct file *file, loff_t offset,
+				struct kvec *vec, int vlen,
+				unsigned long *count);
 __be32 		nfsd_read(struct svc_rqst *, struct svc_fh *,
 				loff_t, struct kvec *, int, unsigned long *);
 __be32 		nfsd_write(struct svc_rqst *, struct svc_fh *, loff_t,