linux-kernel - [PATCH 9/9] cifs: Don't need state locking in smb2_get_mid

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Message-ID: <20251114144253.1853312-10-dhowells@redhat.com>
Date: Fri, 14 Nov 2025 14:42:51 +0000
From: David Howells <dhowells@...hat.com>
To: Steve French <sfrench@...ba.org>
Cc: David Howells <dhowells@...hat.com>,
	Paulo Alcantara <pc@...guebit.org>,
	Shyam Prasad N <sprasad@...rosoft.com>,
	linux-cifs@...r.kernel.org,
	netfs@...ts.linux.dev,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Tom Talpey <tom@...pey.com>
Subject: [PATCH 9/9] cifs: Don't need state locking in smb2_get_mid_entry()

There's no need to get ->srv_lock or ->ses_lock in smb2_get_mid_entry() as
all that happens of relevance (to the lock) inside the locked sections is
the reading of one status value in each.

Replace the locking with READ_ONCE() and use a switch instead of a chain of
if-statements.

Signed-off-by: David Howells <dhowells@...hat.com>
cc: Steve French <sfrench@...ba.org>
cc: Paulo Alcantara <pc@...guebit.org>
cc: Shyam Prasad N <sprasad@...rosoft.com>
cc: Tom Talpey <tom@...pey.com>
cc: linux-cifs@...r.kernel.org
cc: netfs@...ts.linux.dev
cc: linux-fsdevel@...r.kernel.org
---
 fs/smb/client/smb2transport.c | 48 +++++++++++++++--------------------
 1 file changed, 20 insertions(+), 28 deletions(-)

diff --git a/fs/smb/client/smb2transport.c b/fs/smb/client/smb2transport.c
index 6d76b0c6d73d..47eab3753c9e 100644
--- a/fs/smb/client/smb2transport.c
+++ b/fs/smb/client/smb2transport.c
@@ -684,43 +684,35 @@ static int
 smb2_get_mid_entry(struct cifs_ses *ses, struct TCP_Server_Info *server,
 		   struct smb2_hdr *shdr, struct smb_message **smb)
 {
-	spin_lock(&server->srv_lock);
-	if (server->tcpStatus == CifsExiting) {
-		spin_unlock(&server->srv_lock);
+	switch (READ_ONCE(server->tcpStatus)) {
+	case CifsExiting:
 		return -ENOENT;
-	}
-
-	if (server->tcpStatus == CifsNeedReconnect) {
-		spin_unlock(&server->srv_lock);
+	case CifsNeedReconnect:
 		cifs_dbg(FYI, "tcp session dead - return to caller to retry\n");
 		return -EAGAIN;
-	}
-
-	if (server->tcpStatus == CifsNeedNegotiate &&
-	   shdr->Command != SMB2_NEGOTIATE) {
-		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(&ses->ses_lock);
+	case CifsNeedNegotiate:
+		if (shdr->Command != SMB2_NEGOTIATE)
 			return -EAGAIN;
-		}
-		/* else ok - we are setting up session */
+		break;
+	default:
+		break;
 	}
 
-	if (ses->ses_status == SES_EXITING) {
-		if (shdr->Command != SMB2_LOGOFF) {
-			spin_unlock(&ses->ses_lock);
+	switch (READ_ONCE(ses->ses_status)) {
+	case SES_NEW:
+		if (shdr->Command != SMB2_SESSION_SETUP &&
+		    shdr->Command != SMB2_NEGOTIATE)
+			return -EAGAIN;
+			/* else ok - we are setting up session */
+		break;
+	case SES_EXITING:
+		if (shdr->Command != SMB2_LOGOFF)
 			return -EAGAIN;
-		}
 		/* else ok - we are shutting down the session */
+		break;
+	default:
+		break;
 	}
-	spin_unlock(&ses->ses_lock);
 
 	*smb = smb2_mid_entry_alloc(shdr, server);
 	if (*smb == NULL)