CIFS: Respect reconnect in MTU credits calculations

Every time after a session reconnect we don't need to account for
credits obtained in previous sessions. Introduce new struct cifs_credits
which contains both credits value and reconnect instance of the
time those credits were taken. Modify a routine that add credits
back to handle the reconnect instance by assuming zero credits
if the reconnect happened after the credits were obtained and
before we decided to add them back due to some errors during sending.

This patch fixes the MTU credits cases. The subsequent patch
will handle non-MTU ones.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 20 insertions, 7 deletions

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 7291d8289511..6f1a5f504c02 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -67,10 +67,13 @@ change_conf(struct TCP_Server_Info *server)
 }
 
 static void
-smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add,
-		 const int optype)
+smb2_add_credits(struct TCP_Server_Info *server,
+		 const struct cifs_credits *credits, const int optype)
 {
 	int *val, rc = -1;
+	unsigned int add = credits->value;
+	unsigned int instance = credits->instance;
+	bool reconnect_detected = false;
 
 	spin_lock(&server->req_lock);
 	val = server->ops->get_credits_field(server, optype);
@@ -79,8 +82,11 @@ smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add,
 	if (((optype & CIFS_OP_MASK) == CIFS_NEG_OP) && (*val != 0))
 		trace_smb3_reconnect_with_invalid_credits(server->CurrentMid,
 			server->hostname, *val);
+	if ((instance == 0) || (instance == server->reconnect_instance))
+		*val += add;
+	else
+		reconnect_detected = true;
 
-	*val += add;
 	if (*val > 65000) {
 		*val = 65000; /* Don't get near 64K credits, avoid srv bugs */
 		printk_once(KERN_WARNING "server overflowed SMB3 credits\n");
@@ -102,6 +108,10 @@ smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add,
 	spin_unlock(&server->req_lock);
 	wake_up(&server->request_q);
 
+	if (reconnect_detected)
+		cifs_dbg(FYI, "trying to put %d credits from the old server instance %d\n",
+			 add, instance);
+
 	if (server->tcpStatus == CifsNeedReconnect
 	    || server->tcpStatus == CifsExiting)
 		return;
@@ -164,7 +174,7 @@ smb2_get_credits(struct mid_q_entry *mid)
 
 static int
 smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
-		      unsigned int *num, unsigned int *credits)
+		      unsigned int *num, struct cifs_credits *credits)
 {
 	int rc = 0;
 	unsigned int scredits;
@@ -190,7 +200,8 @@ smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
 			/* can deadlock with reopen */
 			if (scredits <= 8) {
 				*num = SMB2_MAX_BUFFER_SIZE;
-				*credits = 0;
+				credits->value = 0;
+				credits->instance = 0;
 				break;
 			}
 
@@ -199,8 +210,10 @@ smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
 			*num = min_t(unsigned int, size,
 				     scredits * SMB2_MAX_BUFFER_SIZE);
 
-			*credits = DIV_ROUND_UP(*num, SMB2_MAX_BUFFER_SIZE);
-			server->credits -= *credits;
+			credits->value =
+				DIV_ROUND_UP(*num, SMB2_MAX_BUFFER_SIZE);
+			credits->instance = server->reconnect_instance;
+			server->credits -= credits->value;
 			server->in_flight++;
 			break;
 		}