NFSD: Modify NFSv4 to use nfsd_read_splice_ok()

Avoid the use of an atomic bitop, and prepare for adding a run-time
switch for using splice reads.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4proc.c

@@ -970,8 +970,11 @@ nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	 * To ensure proper ordering, we therefore turn off zero copy if
 	 * the client wants us to do more in this compound:
 	 */
-	if (!nfsd4_last_compound_op(rqstp))
-		clear_bit(RQ_SPLICE_OK, &rqstp->rq_flags);
+	if (!nfsd4_last_compound_op(rqstp)) {
+		struct nfsd4_compoundargs *argp = rqstp->rq_argp;
+
+		argp->splice_ok = false;
+	}
 
 	/* check stateid */
 	status = nfs4_preprocess_stateid_op(rqstp, cstate, &cstate->current_fh,

fs/nfsd/nfs4xdr.c

@@ -2524,8 +2524,9 @@ nfsd4_decode_compound(struct nfsd4_compoundargs *argp)
 	svc_reserve(argp->rqstp, max_reply + readbytes);
 	argp->rqstp->rq_cachetype = cachethis ? RC_REPLBUFF : RC_NOCACHE;
 
+	argp->splice_ok = nfsd_read_splice_ok(argp->rqstp);
 	if (readcount > 1 || max_reply > PAGE_SIZE - auth_slack)
-		clear_bit(RQ_SPLICE_OK, &argp->rqstp->rq_flags);
+		argp->splice_ok = false;
 
 	return true;
 }
@@ -4375,12 +4376,13 @@ static __be32
 nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 		  union nfsd4_op_u *u)
 {
+	struct nfsd4_compoundargs *argp = resp->rqstp->rq_argp;
 	struct nfsd4_read *read = &u->read;
-	bool splice_ok = test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags);
-	unsigned long maxcount;
 	struct xdr_stream *xdr = resp->xdr;
-	struct file *file;
 	int starting_len = xdr->buf->len;
+	bool splice_ok = argp->splice_ok;
+	unsigned long maxcount;
+	struct file *file;
 	__be32 *p;
 
 	if (nfserr)
@@ -5201,9 +5203,10 @@ static __be32
 nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
 			    struct nfsd4_read *read)
 {
-	bool splice_ok = test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags);
+	struct nfsd4_compoundargs *argp = resp->rqstp->rq_argp;
 	struct file *file = read->rd_nf->nf_file;
 	struct xdr_stream *xdr = resp->xdr;
+	bool splice_ok = argp->splice_ok;
 	unsigned long maxcount;
 	__be32 nfserr, *p;
 

fs/nfsd/xdr4.h

@@ -840,6 +840,7 @@ struct nfsd4_compoundargs {
 	u32				minorversion;
 	u32				client_opcnt;
 	u32				opcnt;
+	bool				splice_ok;
 	struct nfsd4_op			*ops;
 	struct nfsd4_op			iops[8];
 };