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Subject: [PATCH 04/14] SUNRPC: change svc_recv() to return void.
From:   NeilBrown <neilb@suse.de>
To:     Chuck Lever <chuck.lever@oracle.com>,
        Jeff Layton <jlayton@kernel.org>
Cc:     linux-nfs@vger.kernel.org
Date:   Tue, 18 Jul 2023 16:38:08 +1000
Message-ID: <168966228862.11075.10086063375287695723.stgit@noble.brown>
In-Reply-To: <168966227838.11075.2974227708495338626.stgit@noble.brown>
References: <168966227838.11075.2974227708495338626.stgit@noble.brown>
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svc_recv() currently returns a 0 on success or one of two errors:
 - -EAGAIN means no message was successfully received
 - -EINTR means the thread has been told to stop

Previously nfsd would stop as the result of a signal as well as
following kthread_stop().  In that case the difference was useful: EINTR
means stop unconditionally.  EAGAIN means stop if kthread_should_stop(),
continue otherwise.

Now threads only exit when kthread_should_stop() so we don't need the
distinction.

So have all threads test kthread_should_stop() (most do), and return
simple success/failure from svc_recv().
Also change some helpers that svc_recv() uses to not bother with an
error code, returning a bool in once case, and NULL for failure in
another.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/lockd/svc.c                 |    9 +++------
 fs/nfs/callback.c              |    5 +----
 fs/nfsd/nfssvc.c               |    8 ++------
 include/linux/sunrpc/svcsock.h |    2 +-
 net/sunrpc/svc_xprt.c          |   27 +++++++++++----------------
 5 files changed, 18 insertions(+), 33 deletions(-)

diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 91ef139a7757..a43b63e46127 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -116,7 +116,6 @@ static void set_grace_period(struct net *net)
 static int
 lockd(void *vrqstp)
 {
-	int		err = 0;
 	struct svc_rqst *rqstp = vrqstp;
 	struct net *net = &init_net;
 	struct lockd_net *ln = net_generic(net, lockd_net_id);
@@ -139,12 +138,10 @@ lockd(void *vrqstp)
 		timeout = nlmsvc_retry_blocked();
 
 		/*
-		 * Find a socket with data available and call its
-		 * recvfrom routine.
+		 * Find any work to do, such as a socket with data available,
+		 * and do the work.
 		 */
-		err = svc_recv(rqstp, timeout);
-		if (err == -EAGAIN || err == -EINTR)
-			continue;
+		svc_recv(rqstp, timeout);
 	}
 	if (nlmsvc_ops)
 		nlmsvc_invalidate_all();
diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index 2d94384bd6a9..914d2402ca98 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -74,7 +74,6 @@ static int nfs4_callback_up_net(struct svc_serv *serv, struct net *net)
 static int
 nfs4_callback_svc(void *vrqstp)
 {
-	int err;
 	struct svc_rqst *rqstp = vrqstp;
 
 	set_freezable();
@@ -83,9 +82,7 @@ nfs4_callback_svc(void *vrqstp)
 		/*
 		 * Listen for a request on the socket
 		 */
-		err = svc_recv(rqstp, MAX_SCHEDULE_TIMEOUT);
-		if (err == -EAGAIN || err == -EINTR)
-			continue;
+		svc_recv(rqstp, MAX_SCHEDULE_TIMEOUT);
 	}
 
 	svc_exit_thread(rqstp);
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 3e08cc746870..5bf48c33986e 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -953,7 +953,6 @@ nfsd(void *vrqstp)
 	struct svc_xprt *perm_sock = list_entry(rqstp->rq_server->sv_permsocks.next, typeof(struct svc_xprt), xpt_list);
 	struct net *net = perm_sock->xpt_net;
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	int err;
 
 	/* At this point, the thread shares current->fs
 	 * with the init process. We need to create files with the
@@ -972,7 +971,7 @@ nfsd(void *vrqstp)
 	/*
 	 * The main request loop
 	 */
-	for (;;) {
+	while (!kthread_should_stop()) {
 		/* Update sv_maxconn if it has changed */
 		rqstp->rq_server->sv_maxconn = nn->max_connections;
 
@@ -980,10 +979,7 @@ nfsd(void *vrqstp)
 		 * Find a socket with data available and call its
 		 * recvfrom routine.
 		 */
-		while ((err = svc_recv(rqstp, 60*60*HZ)) == -EAGAIN)
-			;
-		if (err == -EINTR)
-			break;
+		svc_recv(rqstp, 60*60*HZ);
 		validate_process_creds();
 	}
 
diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index 55446136499f..fb5c98069356 100644
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -64,7 +64,7 @@ static inline u32 svc_sock_final_rec(struct svc_sock *svsk)
  * Function prototypes.
  */
 void		svc_close_net(struct svc_serv *, struct net *);
-int		svc_recv(struct svc_rqst *, long);
+void		svc_recv(struct svc_rqst *, long);
 void		svc_send(struct svc_rqst *rqstp);
 void		svc_drop(struct svc_rqst *);
 void		svc_sock_update_bufs(struct svc_serv *serv);
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index c808f6d60c99..67825eef8646 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -664,7 +664,7 @@ static void svc_check_conn_limits(struct svc_serv *serv)
 	}
 }
 
-static int svc_alloc_arg(struct svc_rqst *rqstp)
+static bool svc_alloc_arg(struct svc_rqst *rqstp)
 {
 	struct svc_serv *serv = rqstp->rq_server;
 	struct xdr_buf *arg = &rqstp->rq_arg;
@@ -689,7 +689,7 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
 		set_current_state(TASK_IDLE);
 		if (kthread_should_stop()) {
 			set_current_state(TASK_RUNNING);
-			return -EINTR;
+			return false;
 		}
 		trace_svc_alloc_arg_err(pages, ret);
 		memalloc_retry_wait(GFP_KERNEL);
@@ -708,7 +708,7 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
 	arg->tail[0].iov_len = 0;
 
 	rqstp->rq_xid = xdr_zero;
-	return 0;
+	return true;
 }
 
 static bool
@@ -773,9 +773,9 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
 	if (!time_left)
 		percpu_counter_inc(&pool->sp_threads_timedout);
 	if (kthread_should_stop())
-		return ERR_PTR(-EINTR);
+		return NULL;
 	percpu_counter_inc(&pool->sp_threads_no_work);
-	return ERR_PTR(-EAGAIN);
+	return NULL;
 out_found:
 	/* Normally we will wait up to 5 seconds for any required
 	 * cache information to be provided.
@@ -856,32 +856,27 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
  * organised not to touch any cachelines in the shared svc_serv
  * structure, only cachelines in the local svc_pool.
  */
-int svc_recv(struct svc_rqst *rqstp, long timeout)
+void svc_recv(struct svc_rqst *rqstp, long timeout)
 {
 	struct svc_xprt		*xprt = NULL;
 	struct svc_serv		*serv = rqstp->rq_server;
-	int			len, err;
+	int			len;
 
-	err = svc_alloc_arg(rqstp);
-	if (err)
+	if (!svc_alloc_arg(rqstp))
 		goto out;
 
 	try_to_freeze();
 	cond_resched();
-	err = -EINTR;
 	if (kthread_should_stop())
 		goto out;
 
 	xprt = svc_get_next_xprt(rqstp, timeout);
-	if (IS_ERR(xprt)) {
-		err = PTR_ERR(xprt);
+	if (!xprt)
 		goto out;
-	}
 
 	len = svc_handle_xprt(rqstp, xprt);
 
 	/* No data, incomplete (TCP) read, or accept() */
-	err = -EAGAIN;
 	if (len <= 0)
 		goto out_release;
 
@@ -896,12 +891,12 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
 	percpu_counter_inc(&rqstp->rq_pool->sp_messages_arrived);
 	rqstp->rq_stime = ktime_get();
 	svc_process(rqstp);
-	return 0;
+	return;
 out_release:
 	rqstp->rq_res.len = 0;
 	svc_xprt_release(rqstp);
 out:
-	return err;
+	return;
 }
 EXPORT_SYMBOL_GPL(svc_recv);