smb: client: add mid_counter_lock to protect the mid counter counter

This is step 2/4 of a patch series to fix mid_q_entry memory leaks
caused by race conditions in callback execution.

Add a dedicated mid_counter_lock to protect current_mid counter,
separating it from mid_queue_lock which protects pending_mid_q
operations. This reduces lock contention and prepares for finer-
grained locking in subsequent patches.

Changes:
- Add TCP_Server_Info->mid_counter_lock spinlock
- Rename CurrentMid to current_mid for consistency
- Use mid_counter_lock to protect current_mid access
- Update locking documentation in cifsglob.h

This separation allows mid allocation to proceed without blocking
queue operations, improving performance under heavy load.

Signed-off-by: Wang Zhaolong <wangzhaolong@huaweicloud.com>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index e4b577ca48d5..74ad5881ee45 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -358,7 +358,7 @@ static bool cifs_tcp_ses_needs_reconnect(struct TCP_Server_Info *server, int num
 	}
 
 	cifs_dbg(FYI, "Mark tcp session as need reconnect\n");
-	trace_smb3_reconnect(server->CurrentMid, server->conn_id,
+	trace_smb3_reconnect(server->current_mid, server->conn_id,
 			     server->hostname);
 	server->tcpStatus = CifsNeedReconnect;
 
@@ -1242,7 +1242,7 @@ smb2_add_credits_from_hdr(char *buffer, struct TCP_Server_Info *server)
 		spin_unlock(&server->req_lock);
 		wake_up(&server->request_q);
 
-		trace_smb3_hdr_credits(server->CurrentMid,
+		trace_smb3_hdr_credits(server->current_mid,
 				server->conn_id, server->hostname, scredits,
 				le16_to_cpu(shdr->CreditRequest), in_flight);
 		cifs_server_dbg(FYI, "%s: added %u credits total=%d\n",
@@ -1823,6 +1823,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
 	spin_lock_init(&tcp_ses->req_lock);
 	spin_lock_init(&tcp_ses->srv_lock);
 	spin_lock_init(&tcp_ses->mid_queue_lock);
+	spin_lock_init(&tcp_ses->mid_counter_lock);
 	INIT_LIST_HEAD(&tcp_ses->tcp_ses_list);
 	INIT_LIST_HEAD(&tcp_ses->smb_ses_list);
 	INIT_DELAYED_WORK(&tcp_ses->echo, cifs_echo_request);