Merge: Revert "SUNRPC: Revert e0a912e"

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6919

This reverts commit d1711eb, which
reverted the original SUNRPC/TCP corking/uncorking after work to make the
RPC layer use bio_vecs allowing single sock_sendmesg().  The inadvertent
inclusion of this upstream commit causes a major regression where the RPC
header and payload are flushed in separate TCP packets.

JIRA: https://issues.redhat.com/browse/RHEL-92060
Upstream-status: RHEL Only
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>

Approved-by: Scott Mayhew <smayhew@redhat.com>
Approved-by: Olga Kornievskaia <okorniev@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Jan Stancek <jstancek@redhat.com>

Author: jstancek

include/linux/sunrpc/svcsock.h

@@ -35,6 +35,8 @@ struct svc_sock {
 	/* Total length of the data (not including fragment headers)
 	 * received so far in the fragments making up this rpc: */
 	u32			sk_datalen;
+	/* Number of queued send requests */
+	atomic_t		sk_sendqlen;
 
 	struct completion	sk_handshake_done;
 

net/sunrpc/svcsock.c

@@ -1296,18 +1296,23 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
 	svc_tcp_release_ctxt(xprt, rqstp->rq_xprt_ctxt);
 	rqstp->rq_xprt_ctxt = NULL;
 
+	atomic_inc(&svsk->sk_sendqlen);
 	mutex_lock(&xprt->xpt_mutex);
 	if (svc_xprt_is_dead(xprt))
 		goto out_notconn;
+	tcp_sock_set_cork(svsk->sk_sk, true);
 	err = svc_tcp_sendmsg(svsk->sk_sock, xdr, marker, &sent);
 	xdr_free_bvec(xdr);
 	trace_svcsock_tcp_send(xprt, err < 0 ? (long)err : sent);
 	if (err < 0 || sent != (xdr->len + sizeof(marker)))
 		goto out_close;
+	if (atomic_dec_and_test(&svsk->sk_sendqlen))
+		tcp_sock_set_cork(svsk->sk_sk, false);
 	mutex_unlock(&xprt->xpt_mutex);
 	return sent;
 
 out_notconn:
+	atomic_dec(&svsk->sk_sendqlen);
 	mutex_unlock(&xprt->xpt_mutex);
 	return -ENOTCONN;
 out_close:
@@ -1316,6 +1321,7 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
 		  (err < 0) ? "got error" : "sent",
 		  (err < 0) ? err : sent, xdr->len);
 	svc_xprt_deferred_close(xprt);
+	atomic_dec(&svsk->sk_sendqlen);
 	mutex_unlock(&xprt->xpt_mutex);
 	return -EAGAIN;
 }