NFSD: Clean up SPLICE_OK in nfsd4_encode_read()

Do the test_bit() once -- this reduces the number of locked-bus
operations and makes the function a little easier to read.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4xdr.c

@@ -3980,6 +3980,7 @@ static __be32
 nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 		  struct nfsd4_read *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;
@@ -3992,11 +3993,10 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 
 	p = xdr_reserve_space(xdr, 8); /* eof flag and byte count */
 	if (!p) {
-		WARN_ON_ONCE(test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags));
+		WARN_ON_ONCE(splice_ok);
 		return nfserr_resource;
 	}
-	if (resp->xdr->buf->page_len &&
-	    test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags)) {
+	if (resp->xdr->buf->page_len && splice_ok) {
 		WARN_ON_ONCE(1);
 		return nfserr_resource;
 	}
@@ -4005,8 +4005,7 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 	maxcount = min_t(unsigned long, read->rd_length,
 			 (xdr->buf->buflen - xdr->buf->len));
 
-	if (file->f_op->splice_read &&
-	    test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags))
+	if (file->f_op->splice_read && splice_ok)
 		nfserr = nfsd4_encode_splice_read(resp, read, file, maxcount);
 	else
 		nfserr = nfsd4_encode_readv(resp, read, file, maxcount);