cifs: avoid use of global locks for high contention data

During analysis of multichannel perf, it was seen that
the global locks cifs_tcp_ses_lock and GlobalMid_Lock, which
were shared between various data structures were causing a
lot of contention points.

With this change, we're breaking down the use of these locks
by introducing new locks at more granular levels. i.e.
server->srv_lock, ses->ses_lock and tcon->tc_lock to protect
the unprotected fields of server, session and tcon structs;
and server->mid_lock to protect mid related lists and entries
at server level.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 17 insertions, 15 deletions

diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
index 53ff6bc11939..f64922f340b3 100644
--- a/fs/cifs/smb2transport.c
+++ b/fs/cifs/smb2transport.c
@@ -640,13 +640,13 @@ smb2_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 
 	if (!is_signed)
 		return 0;
-	spin_lock(&cifs_tcp_ses_lock);
+	spin_lock(&server->srv_lock);
 	if (server->ops->need_neg &&
 	    server->ops->need_neg(server)) {
-		spin_unlock(&cifs_tcp_ses_lock);
+		spin_unlock(&server->srv_lock);
 		return 0;
 	}
-	spin_unlock(&cifs_tcp_ses_lock);
+	spin_unlock(&server->srv_lock);
 	if (!is_binding && !server->session_estab) {
 		strncpy(shdr->Signature, "BSRSPYL", 8);
 		return 0;
@@ -762,28 +762,30 @@ static int
 smb2_get_mid_entry(struct cifs_ses *ses, struct TCP_Server_Info *server,
 		   struct smb2_hdr *shdr, struct mid_q_entry **mid)
 {
-	spin_lock(&cifs_tcp_ses_lock);
+	spin_lock(&server->srv_lock);
 	if (server->tcpStatus == CifsExiting) {
-		spin_unlock(&cifs_tcp_ses_lock);
+		spin_unlock(&server->srv_lock);
 		return -ENOENT;
 	}
 
 	if (server->tcpStatus == CifsNeedReconnect) {
-		spin_unlock(&cifs_tcp_ses_lock);
+		spin_unlock(&server->srv_lock);
 		cifs_dbg(FYI, "tcp session dead - return to caller to retry\n");
 		return -EAGAIN;
 	}
 
 	if (server->tcpStatus == CifsNeedNegotiate &&
 	   shdr->Command != SMB2_NEGOTIATE) {
-		spin_unlock(&cifs_tcp_ses_lock);
+		spin_unlock(&server->srv_lock);
 		return -EAGAIN;
 	}
+	spin_unlock(&server->srv_lock);
 
+	spin_lock(&ses->ses_lock);
 	if (ses->ses_status == SES_NEW) {
 		if ((shdr->Command != SMB2_SESSION_SETUP) &&
 		    (shdr->Command != SMB2_NEGOTIATE)) {
-			spin_unlock(&cifs_tcp_ses_lock);
+			spin_unlock(&ses->ses_lock);
 			return -EAGAIN;
 		}
 		/* else ok - we are setting up session */
@@ -791,19 +793,19 @@ smb2_get_mid_entry(struct cifs_ses *ses, struct TCP_Server_Info *server,
 
 	if (ses->ses_status == SES_EXITING) {
 		if (shdr->Command != SMB2_LOGOFF) {
-			spin_unlock(&cifs_tcp_ses_lock);
+			spin_unlock(&ses->ses_lock);
 			return -EAGAIN;
 		}
 		/* else ok - we are shutting down the session */
 	}
-	spin_unlock(&cifs_tcp_ses_lock);
+	spin_unlock(&ses->ses_lock);
 
 	*mid = smb2_mid_entry_alloc(shdr, server);
 	if (*mid == NULL)
 		return -ENOMEM;
-	spin_lock(&GlobalMid_Lock);
+	spin_lock(&server->mid_lock);
 	list_add_tail(&(*mid)->qhead, &server->pending_mid_q);
-	spin_unlock(&GlobalMid_Lock);
+	spin_unlock(&server->mid_lock);
 
 	return 0;
 }
@@ -869,13 +871,13 @@ smb2_setup_async_request(struct TCP_Server_Info *server, struct smb_rqst *rqst)
 			(struct smb2_hdr *)rqst->rq_iov[0].iov_base;
 	struct mid_q_entry *mid;
 
-	spin_lock(&cifs_tcp_ses_lock);
+	spin_lock(&server->srv_lock);
 	if (server->tcpStatus == CifsNeedNegotiate &&
 	   shdr->Command != SMB2_NEGOTIATE) {
-		spin_unlock(&cifs_tcp_ses_lock);
+		spin_unlock(&server->srv_lock);
 		return ERR_PTR(-EAGAIN);
 	}
-	spin_unlock(&cifs_tcp_ses_lock);
+	spin_unlock(&server->srv_lock);
 
 	smb2_seq_num_into_buf(server, shdr);