[PATCH v2 2/2] cifs: Fix locking usage for tcon fields

[PATCH v2 2/2] cifs: Fix locking usage for tcon fields

[nspmangalore]

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

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>
---
 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 1db7ab6c2529c..569030b3e68d4 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 f3cb62d914502..0871b9f1f86a6 100644
--- a/fs/smb/client/smb2misc.c
+++ b/fs/smb/client/smb2misc.c
@@ -820,14 +820,14 @@ 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;
@@ -841,7 +841,7 @@ 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 c1aaf77e187b6..0b2abd0fdad11 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -3091,7 +3091,9 @@ 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);
 		}
@@ -3160,13 +3162,9 @@ 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 5d57c895ca37a..c7e086dfb1765 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -4239,7 +4239,9 @@ 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 a584a77431132..191f02344dcdd 100644
--- a/fs/smb/client/trace.h
+++ b/fs/smb/client/trace.h
@@ -189,6 +189,7 @@
 	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") \
-- 
2.43.0