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>
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index e35dc60..2a11efd 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -80,7 +80,7 @@
if (max_vcs < 2)
max_vcs = 0xFFFF;
- write_lock(&cifs_tcp_ses_lock);
+ spin_lock(&cifs_tcp_ses_lock);
if ((ses->need_reconnect) && is_first_ses_reconnect(ses))
goto get_vc_num_exit; /* vcnum will be zero */
for (i = ses->server->srv_count - 1; i < max_vcs; i++) {
@@ -112,7 +112,7 @@
vcnum = i;
ses->vcnum = vcnum;
get_vc_num_exit:
- write_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&cifs_tcp_ses_lock);
return cpu_to_le16(vcnum);
}