Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
index 3c15a99..195b40c 100644
--- a/net/sunrpc/backchannel_rqst.c
+++ b/net/sunrpc/backchannel_rqst.c
@@ -31,25 +31,20 @@
 #define RPCDBG_FACILITY	RPCDBG_TRANS
 #endif
 
+#define BC_MAX_SLOTS	64U
+
+unsigned int xprt_bc_max_slots(struct rpc_xprt *xprt)
+{
+	return BC_MAX_SLOTS;
+}
+
 /*
  * Helper routines that track the number of preallocation elements
  * on the transport.
  */
 static inline int xprt_need_to_requeue(struct rpc_xprt *xprt)
 {
-	return xprt->bc_alloc_count < atomic_read(&xprt->bc_free_slots);
-}
-
-static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n)
-{
-	atomic_add(n, &xprt->bc_free_slots);
-	xprt->bc_alloc_count += n;
-}
-
-static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n)
-{
-	atomic_sub(n, &xprt->bc_free_slots);
-	return xprt->bc_alloc_count -= n;
+	return xprt->bc_alloc_count < xprt->bc_alloc_max;
 }
 
 /*
@@ -91,7 +86,6 @@
 		return NULL;
 
 	req->rq_xprt = xprt;
-	INIT_LIST_HEAD(&req->rq_list);
 	INIT_LIST_HEAD(&req->rq_bc_list);
 
 	/* Preallocate one XDR receive buffer */
@@ -146,6 +140,9 @@
 
 	dprintk("RPC:       setup backchannel transport\n");
 
+	if (min_reqs > BC_MAX_SLOTS)
+		min_reqs = BC_MAX_SLOTS;
+
 	/*
 	 * We use a temporary list to keep track of the preallocated
 	 * buffers.  Once we're done building the list we splice it
@@ -173,7 +170,9 @@
 	 */
 	spin_lock(&xprt->bc_pa_lock);
 	list_splice(&tmp_list, &xprt->bc_pa_list);
-	xprt_inc_alloc_count(xprt, min_reqs);
+	xprt->bc_alloc_count += min_reqs;
+	xprt->bc_alloc_max += min_reqs;
+	atomic_add(min_reqs, &xprt->bc_slot_count);
 	spin_unlock(&xprt->bc_pa_lock);
 
 	dprintk("RPC:       setup backchannel transport done\n");
@@ -198,7 +197,7 @@
 /**
  * xprt_destroy_backchannel - Destroys the backchannel preallocated structures.
  * @xprt:	the transport holding the preallocated strucures
- * @max_reqs	the maximum number of preallocated structures to destroy
+ * @max_reqs:	the maximum number of preallocated structures to destroy
  *
  * Since these structures may have been allocated by multiple calls
  * to xprt_setup_backchannel, we only destroy up to the maximum number
@@ -221,11 +220,13 @@
 		goto out;
 
 	spin_lock_bh(&xprt->bc_pa_lock);
-	xprt_dec_alloc_count(xprt, max_reqs);
+	xprt->bc_alloc_max -= min(max_reqs, xprt->bc_alloc_max);
 	list_for_each_entry_safe(req, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 		dprintk("RPC:        req=%p\n", req);
 		list_del(&req->rq_bc_pa_list);
 		xprt_free_allocation(req);
+		xprt->bc_alloc_count--;
+		atomic_dec(&xprt->bc_slot_count);
 		if (--max_reqs == 0)
 			break;
 	}
@@ -236,30 +237,30 @@
 		list_empty(&xprt->bc_pa_list) ? "true" : "false");
 }
 
-static struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt, __be32 xid)
+static struct rpc_rqst *xprt_get_bc_request(struct rpc_xprt *xprt, __be32 xid,
+		struct rpc_rqst *new)
 {
 	struct rpc_rqst *req = NULL;
 
 	dprintk("RPC:       allocate a backchannel request\n");
-	if (atomic_read(&xprt->bc_free_slots) <= 0)
-		goto not_found;
 	if (list_empty(&xprt->bc_pa_list)) {
-		req = xprt_alloc_bc_req(xprt, GFP_ATOMIC);
-		if (!req)
+		if (!new)
 			goto not_found;
-		list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
+		if (atomic_read(&xprt->bc_slot_count) >= BC_MAX_SLOTS)
+			goto not_found;
+		list_add_tail(&new->rq_bc_pa_list, &xprt->bc_pa_list);
 		xprt->bc_alloc_count++;
+		atomic_inc(&xprt->bc_slot_count);
 	}
 	req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
 				rq_bc_pa_list);
 	req->rq_reply_bytes_recvd = 0;
-	req->rq_bytes_sent = 0;
 	memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
 			sizeof(req->rq_private_buf));
 	req->rq_xid = xid;
 	req->rq_connect_cookie = xprt->connect_cookie;
-not_found:
 	dprintk("RPC:       backchannel req=%p\n", req);
+not_found:
 	return req;
 }
 
@@ -293,6 +294,7 @@
 	if (xprt_need_to_requeue(xprt)) {
 		list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
 		xprt->bc_alloc_count++;
+		atomic_inc(&xprt->bc_slot_count);
 		req = NULL;
 	}
 	spin_unlock_bh(&xprt->bc_pa_lock);
@@ -305,8 +307,8 @@
 		 */
 		dprintk("RPC:       Last session removed req=%p\n", req);
 		xprt_free_allocation(req);
-		return;
 	}
+	xprt_put(xprt);
 }
 
 /*
@@ -322,18 +324,27 @@
  */
 struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
 {
-	struct rpc_rqst *req;
+	struct rpc_rqst *req, *new = NULL;
 
-	spin_lock(&xprt->bc_pa_lock);
-	list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
-		if (req->rq_connect_cookie != xprt->connect_cookie)
-			continue;
-		if (req->rq_xid == xid)
-			goto found;
-	}
-	req = xprt_alloc_bc_request(xprt, xid);
+	do {
+		spin_lock(&xprt->bc_pa_lock);
+		list_for_each_entry(req, &xprt->bc_pa_list, rq_bc_pa_list) {
+			if (req->rq_connect_cookie != xprt->connect_cookie)
+				continue;
+			if (req->rq_xid == xid)
+				goto found;
+		}
+		req = xprt_get_bc_request(xprt, xid, new);
 found:
-	spin_unlock(&xprt->bc_pa_lock);
+		spin_unlock(&xprt->bc_pa_lock);
+		if (new) {
+			if (req != new)
+				xprt_free_allocation(new);
+			break;
+		} else if (req)
+			break;
+		new = xprt_alloc_bc_req(xprt, GFP_KERNEL);
+	} while (new);
 	return req;
 }
 
@@ -350,13 +361,14 @@
 
 	spin_lock(&xprt->bc_pa_lock);
 	list_del(&req->rq_bc_pa_list);
-	xprt_dec_alloc_count(xprt, 1);
+	xprt->bc_alloc_count--;
 	spin_unlock(&xprt->bc_pa_lock);
 
 	req->rq_private_buf.len = copied;
 	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 
 	dprintk("RPC:       add callback request to list\n");
+	xprt_get(xprt);
 	spin_lock(&bc_serv->sv_cb_lock);
 	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
 	wake_up(&bc_serv->sv_cb_waitq);