cifs: Fix locking usage for tcon fields

[ Upstream commit 96c4af4 ]

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>

Author: sprasad-microsoft

fs/smb/client/cached_dir.c

@@ -769,11 +769,11 @@ static void cfids_laundromat_worker(struct work_struct *work)
 
 		dput(dentry);
 		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
 			/*

fs/smb/client/smb2misc.c

@@ -807,14 +807,14 @@ 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;
@@ -828,7 +828,7 @@ 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);

fs/smb/client/smb2ops.c

@@ -3000,7 +3000,9 @@ 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);
 		}
@@ -3065,13 +3067,9 @@ 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);

fs/smb/client/smb2pdu.c

@@ -4180,7 +4180,9 @@ 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);

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") \