cifs: convert cifs_tcp_ses_lock from a rwlock to a spinlock

cifs_tcp_ses_lock is a rwlock with protects the cifs_tcp_ses_list,
server->smb_ses_list and the ses->tcon_list. It also protects a few
ref counters in server, ses and tcon. In most cases the critical section
doesn't seem to be large, in a few cases where it is slightly large, there
seem to be really no benefit from concurrent access. I briefly considered RCU
mechanism but it appears to me that there is no real need.

Replace it with a spinlock and get rid of the last rwlock in the cifs code.

Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 18ee0adda306..28337cba0295 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -703,7 +703,7 @@ GLOBAL_EXTERN struct list_head		cifs_tcp_ses_list;
  * the reference counters for the server, smb session, and tcon. Finally,
  * changes to the tcon->tidStatus should be done while holding this lock.
  */
-GLOBAL_EXTERN rwlock_t          cifs_tcp_ses_lock;
+GLOBAL_EXTERN spinlock_t                cifs_tcp_ses_lock;
 
 /*
  * This lock protects the cifs_file->llist and cifs_file->flist