add new module parameter 'enable_oplocks'

Thus spake Jeff Layton:

"Making that a module parm would allow you to set that parameter at boot
time without needing to add special startup scripts. IMO, all of the
procfile "switches" under /proc/fs/cifs should be module parms
instead."

This patch doesn't alter the default behavior (Oplocks are enabled by
default).

To disable oplocks when loading the module, use

   modprobe cifs enable_oplocks=0

(any of '0' or 'n' or 'N' conventions can be used).

To disable oplocks at runtime using the new interface, use

   echo 0 > /sys/module/cifs/parameters/enable_oplocks

The older /proc/fs/cifs/OplockEnabled interface will be deprecated
after two releases. A subsequent patch will add an warning message
about this deprecation.

Changes since v2:
   - make enable_oplocks a 'bool'

Changes since v1:
   - eliminate the use of extra variable by renaming the old one to
     enable_oplocks and make it an 'int' type.

Reported-by: Alexander Swen <alex@swen.nu>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index aa8fe7c..5c29721 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -53,7 +53,7 @@
 int cifsFYI = 0;
 int cifsERROR = 1;
 int traceSMB = 0;
-unsigned int oplockEnabled = 1;
+bool enable_oplocks = true;
 unsigned int linuxExtEnabled = 1;
 unsigned int lookupCacheEnabled = 1;
 unsigned int multiuser_mount = 0;
@@ -82,6 +82,10 @@
 MODULE_PARM_DESC(echo_retries, "Number of echo attempts before giving up and "
 			       "reconnecting server. Default: 5. 0 means "
 			       "never reconnect.");
+module_param(enable_oplocks, bool, 0644);
+MODULE_PARM_DESC(enable_oplocks, "Enable or disable oplocks (bool). Default:"
+				 "y/Y/1");
+
 extern mempool_t *cifs_sm_req_poolp;
 extern mempool_t *cifs_req_poolp;
 extern mempool_t *cifs_mid_poolp;