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, 8 insertions, 9 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 2946dab0718f..a1e96620b097 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1031,24 +1031,24 @@ static int cifs_oplock_thread(void *dummyarg)
 static int cifs_dnotify_thread(void *dummyarg)
 {
         struct list_head *tmp;
-        struct cifsSesInfo *ses;
+        struct TCP_Server_Info *server;
 
         do {
                 if (try_to_freeze())
                         continue;
                 set_current_state(TASK_INTERRUPTIBLE);
                 schedule_timeout(15*HZ);
-                read_lock(&GlobalSMBSeslock);
                 /* check if any stuck requests that need
                    to be woken up and wakeq so the
                    thread can wake up and error out */
-                list_for_each(tmp, &GlobalSMBSessionList) {
-                        ses = list_entry(tmp, struct cifsSesInfo,
-                                cifsSessionList);
-                        if (ses->server && atomic_read(&ses->server->inFlight))
-                                wake_up_all(&ses->server->response_q);
+                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);
+                        if (atomic_read(&server->inFlight))
+                                wake_up_all(&server->response_q);
                 }
-                read_unlock(&GlobalSMBSeslock);
+                read_unlock(&cifs_tcp_ses_lock);
         } while (!kthread_should_stop());
 
         return 0;
@@ -1060,7 +1060,6 @@ init_cifs(void)
         int rc = 0;
         cifs_proc_init();
         INIT_LIST_HEAD(&cifs_tcp_ses_list);
-        INIT_LIST_HEAD(&GlobalSMBSessionList); /* BB to be removed by jl */
         INIT_LIST_HEAD(&GlobalTreeConnectionList); /* BB to be removed by jl */
         INIT_LIST_HEAD(&GlobalOplock_Q);
 #ifdef CONFIG_CIFS_EXPERIMENTAL