[PATCH 6.18 681/752] cifs: Fix locking usage for tcon fields

Sasha Levin
2026-02-28T17:58:17Z

From: Shyam Prasad N <sprasad@microsoft.com>

[ Upstream commit 96c4af418586ee9a6aab61738644366426e05316 ]

We used to use the cifs_tcp_ses_lock to protect a lot of objects
that are not just the server, ses or tcon lists. We later introduced
srv_lock, ses_lock and tc_lock to protect fields within the
corresponding structs. This was done to provide a more granular
protection and avoid unnecessary serialization.

There were still a couple of uses of cifs_tcp_ses_lock to provide
tcon fields. In this patch, I've replaced them with tc_lock.

Cc: stable@vger.kernel.org
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/smb/client/cached_dir.c | 4 ++--
fs/smb/client/smb2misc.c | 6 +++---
fs/smb/client/smb2ops.c | 8 +++-----
fs/smb/client/smb2pdu.c | 2 ++
fs/smb/client/trace.h | 1 +
5 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
index e3ea6fe7edb47..09939fe9666ea 100644
--- a/fs/smb/client/cached_dir.c
+++ b/fs/smb/client/cached_dir.c
@@ -788,11 +788,11 @@ static void cfids_laundromat_worker(struct work_struct *work)
cfid->dentry = NULL;

if (cfid->is_open) {
- spin_lock(&cifs_tcp_ses_lock);
+ spin_lock(&cfid->tcon->tc_lock);
++cfid->tcon->tc_count;
trace_smb3_tcon_ref(cfid->tcon->debug_id, cfid->tcon->tc_count,
netfs_trace_tcon_ref_get_cached_laundromat);
- spin_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&cfid->tcon->tc_lock);
queue_work(serverclose_wq, &cfid->close_work);
} else
/*
diff --git a/fs/smb/client/smb2misc.c b/fs/smb/client/smb2misc.c
index 96bfe4c63ccf9..a6fc8ff398ebf 100644
--- a/fs/smb/client/smb2misc.c
+++ b/fs/smb/client/smb2misc.c
@@ -819,14 +819,14 @@ smb2_handle_cancelled_close(struct cifs_tcon *tcon, __u64 persistent_fid,
int rc;

cifs_dbg(FYI, "%s: tc_count=%d\n", __func__, tcon->tc_count);
- spin_lock(&cifs_tcp_ses_lock);
+ spin_lock(&tcon->tc_lock);
if (tcon->tc_count <= 0) {
struct TCP_Server_Info *server = NULL;

trace_smb3_tcon_ref(tcon->debug_id, tcon->tc_count,
netfs_trace_tcon_ref_see_cancelled_close);
WARN_ONCE(tcon->tc_count < 0, "tcon refcount is negative");
- spin_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&tcon->tc_lock);

if (tcon->ses) {
server = tcon->ses->server;
@@ -840,7 +840,7 @@ smb2_handle_cancelled_close(struct cifs_tcon *tcon, __u64 persistent_fid,
tcon->tc_count++;
trace_smb3_tcon_ref(tcon->debug_id, tcon->tc_count,
netfs_trace_tcon_ref_get_cancelled_close);
- spin_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&tcon->tc_lock);

rc = __smb2_handle_cancelled_cmd(tcon, SMB2_CLOSE_HE, 0,
persistent_fid, volatile_fid);
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index c3c5fddb2caab..1b404def355e9 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -3074,7 +3074,9 @@ smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
struct cifs_tcon,
tcon_list);
if (tcon) {
+ spin_lock(&tcon->tc_lock);
tcon->tc_count++;
+ spin_unlock(&tcon->tc_lock);
trace_smb3_tcon_ref(tcon->debug_id, tcon->tc_count,
netfs_trace_tcon_ref_get_dfs_refer);
}
@@ -3143,13 +3145,9 @@ smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
out:
if (tcon && !tcon->ipc) {
/* ipc tcons are not refcounted */
- spin_lock(&cifs_tcp_ses_lock);
- tcon->tc_count--;
+ cifs_put_tcon(tcon, netfs_trace_tcon_ref_put_dfs_refer);
trace_smb3_tcon_ref(tcon->debug_id, tcon->tc_count,
netfs_trace_tcon_ref_dec_dfs_refer);
- /* tc_count can never go negative */
- WARN_ON(tcon->tc_count < 0);
- spin_unlock(&cifs_tcp_ses_lock);
}
kfree(utf16_path);
kfree(dfs_req);
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index e661d40213eab..8082507586e81 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -4174,7 +4174,9 @@ void smb2_reconnect_server(struct work_struct *work)

list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
if (tcon->need_reconnect || tcon->need_reopen_files) {
+ spin_lock(&tcon->tc_lock);
tcon->tc_count++;
+ spin_unlock(&tcon->tc_lock);
trace_smb3_tcon_ref(tcon->debug_id, tcon->tc_count,
netfs_trace_tcon_ref_get_reconnect_server);
list_add_tail(&tcon->rlist, &tmp_list);
diff --git a/fs/smb/client/trace.h b/fs/smb/client/trace.h
index 28e00c34df1cb..e592b2627119f 100644
--- a/fs/smb/client/trace.h
+++ b/fs/smb/client/trace.h
@@ -59,6 +59,7 @@
EM(netfs_trace_tcon_ref_put_cancelled_close_fid, "PUT Cn-Fid") \
EM(netfs_trace_tcon_ref_put_cancelled_mid, "PUT Cn-Mid") \
EM(netfs_trace_tcon_ref_put_mnt_ctx, "PUT MntCtx") \
+ EM(netfs_trace_tcon_ref_put_dfs_refer, "PUT DfsRfr") \
EM(netfs_trace_tcon_ref_put_reconnect_server, "PUT Reconn") \
EM(netfs_trace_tcon_ref_put_tlink, "PUT Tlink ") \
EM(netfs_trace_tcon_ref_see_cancelled_close, "SEE Cn-Cls") \
--
2.51.0