cifs: reinstate sharing of SMB sessions sans races

We do this by abandoning the global list of SMB sessions and instead
moving to a per-server list. This entails adding a new list head to the
TCP_Server_Info struct. The refcounting for the cifsSesInfo is moved to
a non-atomic variable. We have to protect it by a lock anyway, so there's
no benefit to making it an atomic. The list and refcount are protected
by the global cifs_tcp_ses_lock.

The patch also adds a new routines to find and put SMB sessions and
that properly take and put references under the lock.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 27 insertions, 26 deletions

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index 40b5108fb4f..59841a68b0b 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -107,9 +107,9 @@ void cifs_dump_mids(struct TCP_Server_Info *server)
 #ifdef CONFIG_PROC_FS
 static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 {
-	struct list_head *tmp;
-	struct list_head *tmp1;
+	struct list_head *tmp, *tmp2, *tmp3;
 	struct mid_q_entry *mid_entry;
+	struct TCP_Server_Info *server;
 	struct cifsSesInfo *ses;
 	struct cifsTconInfo *tcon;
 	int i;
@@ -122,43 +122,45 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 	seq_printf(m, "Servers:");
 
 	i = 0;
-	read_lock(&GlobalSMBSeslock);
-	list_for_each(tmp, &GlobalSMBSessionList) {
+	read_lock(&cifs_tcp_ses_lock);
+	list_for_each(tmp, &cifs_tcp_ses_list) {
+		server = list_entry(tmp, struct TCP_Server_Info,
+				    tcp_ses_list);
 		i++;
-		ses = list_entry(tmp, struct cifsSesInfo, cifsSessionList);
-		if ((ses->serverDomain == NULL) || (ses->serverOS == NULL) ||
-		   (ses->serverNOS == NULL)) {
-			seq_printf(m, "\nentry for %s not fully "
-					"displayed\n\t", ses->serverName);
-		} else {
-			seq_printf(m,
+		list_for_each(tmp2, &server->smb_ses_list) {
+			ses = list_entry(tmp2, struct cifsSesInfo,
+					 smb_ses_list);
+			if ((ses->serverDomain == NULL) ||
+				(ses->serverOS == NULL) ||
+				(ses->serverNOS == NULL)) {
+				seq_printf(m, "\nentry for %s not fully "
+					   "displayed\n\t", ses->serverName);
+			} else {
+				seq_printf(m,
 				    "\n%d) Name: %s  Domain: %s Mounts: %d OS:"
 				    " %s  \n\tNOS: %s\tCapability: 0x%x\n\tSMB"
 				    " session status: %d\t",
 				i, ses->serverName, ses->serverDomain,
-				atomic_read(&ses->inUse),
-				ses->serverOS, ses->serverNOS,
+				ses->ses_count, ses->serverOS, ses->serverNOS,
 				ses->capabilities, ses->status);
-		}
-		if (ses->server) {
+			}
 			seq_printf(m, "TCP status: %d\n\tLocal Users To "
-				    "Server: %d SecMode: 0x%x Req On Wire: %d",
-				ses->server->tcpStatus,
-				ses->server->srv_count,
-				ses->server->secMode,
-				atomic_read(&ses->server->inFlight));
+				   "Server: %d SecMode: 0x%x Req On Wire: %d",
+				   server->tcpStatus, server->srv_count,
+				   server->secMode,
+				   atomic_read(&server->inFlight));
 
 #ifdef CONFIG_CIFS_STATS2
 			seq_printf(m, " In Send: %d In MaxReq Wait: %d",
-				atomic_read(&ses->server->inSend),
-				atomic_read(&ses->server->num_waiters));
+				atomic_read(&server->inSend),
+				atomic_read(&server->num_waiters));
 #endif
 
 			seq_puts(m, "\nMIDs:\n");
 
 			spin_lock(&GlobalMid_Lock);
-			list_for_each(tmp1, &ses->server->pending_mid_q) {
-				mid_entry = list_entry(tmp1, struct
+			list_for_each(tmp3, &server->pending_mid_q) {
+				mid_entry = list_entry(tmp3, struct
 					mid_q_entry,
 					qhead);
 				seq_printf(m, "State: %d com: %d pid:"
@@ -171,9 +173,8 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 			}
 			spin_unlock(&GlobalMid_Lock);
 		}
-
 	}
-	read_unlock(&GlobalSMBSeslock);
+	read_unlock(&cifs_tcp_ses_lock);
 	seq_putc(m, '\n');
 
 	seq_puts(m, "Shares:");