From 0ab83f3152dc67da643844d91b70ef9eb98a723f Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Mon, 9 Sep 2019 22:57:11 -0500
Subject: [PATCH] smb3: display max credits used at any one time

Displayed in /proc/fs/cifs/Stats once for each
socket we are connected to.

This allows us to find out what the maximum load we
put on a server was.  Except for large writes which can use
multiple credits this would normally equal the maximum number
of requests that had been in flight (at any one time). Note that
/proc/fs/cifs/Stats can be reset if you want to look at a
maximum in flight credits over a small period of time.

Sample output (immediately after mount):

Resources in use
CIFS Session: 1
Share (unique mount targets): 2
SMB Request/Response Buffer: 1 Pool size: 5
SMB Small Req/Resp Buffer: 1 Pool size: 30
Operations (MIDs): 0

0 session 0 share reconnects
Total vfs operations: 5 maximum at one time: 2

Max credits in flight: 2
1) \\localhost\scratch
SMBs: 18
Bytes read: 0  Bytes written: 0
...

Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/cifs/cifs_debug.c | 2 ++
 fs/cifs/cifsglob.h   | 1 +
 fs/cifs/connect.c    | 1 +
 fs/cifs/smb2ops.c    | 2 ++
 fs/cifs/transport.c  | 4 ++++
 5 files changed, 10 insertions(+)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index a38d796f5ffe..dc543ca801bf 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -452,6 +452,7 @@ static ssize_t cifs_stats_proc_write(struct file *file,
 		list_for_each(tmp1, &cifs_tcp_ses_list) {
 			server = list_entry(tmp1, struct TCP_Server_Info,
 					    tcp_ses_list);
+			server->max_in_flight = 0;
 #ifdef CONFIG_CIFS_STATS2
 			for (i = 0; i < NUMBER_OF_SMB2_COMMANDS; i++) {
 				atomic_set(&server->num_cmds[i], 0);
@@ -526,6 +527,7 @@ static int cifs_stats_proc_show(struct seq_file *m, void *v)
 	list_for_each(tmp1, &cifs_tcp_ses_list) {
 		server = list_entry(tmp1, struct TCP_Server_Info,
 				    tcp_ses_list);
+		seq_printf(m, "\nMax credits in flight: %d", server->max_in_flight);
 #ifdef CONFIG_CIFS_STATS2
 		seq_puts(m, "\nTotal time spent processing by command. Time ");
 		seq_printf(m, "units are jiffies (%d per second)\n", HZ);
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 6987fbc5a24a..ef2199913217 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -677,6 +677,7 @@ struct TCP_Server_Info {
 	unsigned int credits;  /* send no more requests at once */
 	unsigned int max_credits; /* can override large 32000 default at mnt */
 	unsigned int in_flight;  /* number of requests on the wire to server */
+	unsigned int max_in_flight; /* max number of requests that were on wire */
 	spinlock_t req_lock;  /* protect the two values above */
 	struct mutex srv_mutex;
 	struct task_struct *tsk;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index e70112d67b0e..df1ccb581828 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2728,6 +2728,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 	tcp_ses->tcp_nodelay = volume_info->sockopt_tcp_nodelay;
 	tcp_ses->rdma = volume_info->rdma;
 	tcp_ses->in_flight = 0;
+	tcp_ses->max_in_flight = 0;
 	tcp_ses->credits = 1;
 	init_waitqueue_head(&tcp_ses->response_q);
 	init_waitqueue_head(&tcp_ses->request_q);
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index f04cf62ff91d..8546e63bb9b9 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -203,6 +203,8 @@ smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
 			credits->instance = server->reconnect_instance;
 			server->credits -= credits->value;
 			server->in_flight++;
+			if (server->in_flight > server->max_in_flight)
+				server->max_in_flight = server->in_flight;
 			break;
 		}
 	}
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 4fccb90492e9..308ad0f495e1 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -532,6 +532,8 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 	if ((flags & CIFS_TIMEOUT_MASK) == CIFS_NON_BLOCKING) {
 		/* oplock breaks must not be held up */
 		server->in_flight++;
+		if (server->in_flight > server->max_in_flight)
+			server->max_in_flight = server->in_flight;
 		*credits -= 1;
 		*instance = server->reconnect_instance;
 		spin_unlock(&server->req_lock);
@@ -608,6 +610,8 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 			if ((flags & CIFS_TIMEOUT_MASK) != CIFS_BLOCKING_OP) {
 				*credits -= num_credits;
 				server->in_flight += num_credits;
+				if (server->in_flight > server->max_in_flight)
+					server->max_in_flight = server->in_flight;
 				*instance = server->reconnect_instance;
 			}
 			spin_unlock(&server->req_lock);
-- 
2.20.1

