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, 2 insertions, 4 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 313f7bfedec7..631a99f72f22 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -195,14 +195,14 @@ struct cifsUidInfo {
  * Session structure.  One of these for each uid session with a particular host
  */
 struct cifsSesInfo {
-        struct list_head cifsSessionList;
+        struct list_head smb_ses_list;
         struct list_head tcon_list;
         struct semaphore sesSem;
 #if 0
         struct cifsUidInfo *uidInfo;    /* pointer to user info */
 #endif
         struct TCP_Server_Info *server; /* pointer to server info */
-        atomic_t inUse; /* # of mounts (tree connections) on this ses */
+        int ses_count;          /* reference counter */
         enum statusEnum status;
         unsigned overrideSecFlg;  /* if non-zero override global sec flags */
         __u16 ipc_tid;          /* special tid for connection to IPC share */
@@ -602,8 +602,6 @@ GLOBAL_EXTERN struct list_head		cifs_tcp_ses_list;
 
 /* protects cifs_tcp_ses_list and srv_count for each tcp session */
 GLOBAL_EXTERN rwlock_t          cifs_tcp_ses_lock;
-
-GLOBAL_EXTERN struct list_head GlobalSMBSessionList; /* BB to be removed by jl*/
 GLOBAL_EXTERN struct list_head GlobalTreeConnectionList; /* BB to be removed */
 GLOBAL_EXTERN rwlock_t GlobalSMBSeslock;  /* protects list inserts on 3 above */