[PATCH 4/9] SUNRPC: Make num_reqs a non-atomic integer

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

If recording xprt->stat.max_slots is moved into xprt_alloc_slot,
then xprt->num_reqs is never manipulated outside
xprt->reserve_lock. There's no longer a need for xprt->num_reqs to
be atomic.

Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 include/linux/sunrpc/xprt.h |    2 +-
 net/sunrpc/xprt.c           |   17 +++++++++--------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index ad322ce..5fea0fb 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -197,7 +197,7 @@ struct rpc_xprt {
 	struct list_head	free;		/* free slots */
 	unsigned int		max_reqs;	/* max number of slots */
 	unsigned int		min_reqs;	/* min number of slots */
-	atomic_t		num_reqs;	/* total slots */
+	unsigned int		num_reqs;	/* total slots */
 	unsigned long		state;		/* transport state */
 	unsigned char		resvport   : 1; /* use a reserved port */
 	atomic_t		swapper;	/* we're swapping over this
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 73f05a1..70f0050 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1009,7 +1009,7 @@ void xprt_transmit(struct rpc_task *task)
 	struct rpc_rqst	*req = task->tk_rqstp;
 	struct rpc_xprt	*xprt = req->rq_xprt;
 	unsigned int connect_cookie;
-	int status, numreqs;
+	int status;
 
 	dprintk("RPC: %5u xprt_transmit(%u)\n", task->tk_pid, req->rq_slen);
 
@@ -1047,9 +1047,6 @@ void xprt_transmit(struct rpc_task *task)
 
 	xprt->ops->set_retrans_timeout(task);
 
-	numreqs = atomic_read(&xprt->num_reqs);
-	if (numreqs > xprt->stat.max_slots)
-		xprt->stat.max_slots = numreqs;
 	xprt->stat.sends++;
 	xprt->stat.req_u += xprt->stat.sends - xprt->stat.recvs;
 	xprt->stat.bklog_u += xprt->backlog.qlen;
@@ -1111,14 +1108,15 @@ static struct rpc_rqst *xprt_dynamic_alloc_slot(struct rpc_xprt *xprt)
 {
 	struct rpc_rqst *req = ERR_PTR(-EAGAIN);
 
-	if (!atomic_add_unless(&xprt->num_reqs, 1, xprt->max_reqs))
+	if (xprt->num_reqs >= xprt->max_reqs)
 		goto out;
+	++xprt->num_reqs;
 	spin_unlock(&xprt->reserve_lock);
 	req = kzalloc(sizeof(struct rpc_rqst), GFP_NOFS);
 	spin_lock(&xprt->reserve_lock);
 	if (req != NULL)
 		goto out;
-	atomic_dec(&xprt->num_reqs);
+	--xprt->num_reqs;
 	req = ERR_PTR(-ENOMEM);
 out:
 	return req;
@@ -1126,7 +1124,8 @@ static struct rpc_rqst *xprt_dynamic_alloc_slot(struct rpc_xprt *xprt)
 
 static bool xprt_dynamic_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
 {
-	if (atomic_add_unless(&xprt->num_reqs, -1, xprt->min_reqs)) {
+	if (xprt->num_reqs > xprt->min_reqs) {
+		--xprt->num_reqs;
 		kfree(req);
 		return true;
 	}
@@ -1162,6 +1161,8 @@ void xprt_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
 	spin_unlock(&xprt->reserve_lock);
 	return;
 out_init_req:
+	xprt->stat.max_slots = max_t(unsigned int, xprt->stat.max_slots,
+				     xprt->num_reqs);
 	task->tk_status = 0;
 	task->tk_rqstp = req;
 	xprt_request_init(task, xprt);
@@ -1229,7 +1230,7 @@ struct rpc_xprt *xprt_alloc(struct net *net, size_t size,
 	else
 		xprt->max_reqs = num_prealloc;
 	xprt->min_reqs = num_prealloc;
-	atomic_set(&xprt->num_reqs, num_prealloc);
+	xprt->num_reqs = num_prealloc;
 
 	return xprt;
 

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