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>

fs/cifs/cifs_debug.c

@@ -511,7 +511,7 @@ static const struct file_operations cifsFYI_proc_fops = {
 
 static int cifs_oplock_proc_show(struct seq_file *m, void *v)
 {
-	seq_printf(m, "%d\n", oplockEnabled);
+	seq_printf(m, "%d\n", enable_oplocks);
 	return 0;
 }
 
@@ -530,9 +530,9 @@ static ssize_t cifs_oplock_proc_write(struct file *file,
 	if (rc)
 		return rc;
 	if (c == '0' || c == 'n' || c == 'N')
-		oplockEnabled = 0;
+		enable_oplocks = false;
 	else if (c == '1' || c == 'y' || c == 'Y')
-		oplockEnabled = 1;
+		enable_oplocks = true;
 
 	return count;
 }

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_param(echo_retries, ushort, 0644);
 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;

fs/cifs/cifsglob.h

@@ -964,7 +964,8 @@ GLOBAL_EXTERN unsigned int multiuser_mount; /* if enabled allows new sessions
 				to be established on existing mount if we
 				have the uid/password or Kerberos credential
 				or equivalent for current user */
-GLOBAL_EXTERN unsigned int oplockEnabled;
+/* enable or disable oplocks */
+GLOBAL_EXTERN bool enable_oplocks;
 GLOBAL_EXTERN unsigned int lookupCacheEnabled;
 GLOBAL_EXTERN unsigned int global_secflags;	/* if on, session setup sent
 				with more secure ntlmssp2 challenge/resp */

fs/cifs/dir.c

@@ -171,7 +171,7 @@ cifs_create(struct inode *inode, struct dentry *direntry, int mode,
 	}
 	tcon = tlink_tcon(tlink);
 
-	if (oplockEnabled)
+	if (enable_oplocks)
 		oplock = REQ_OPLOCK;
 
 	if (nd)

fs/cifs/file.c

@@ -371,7 +371,7 @@ int cifs_open(struct inode *inode, struct file *file)
 	cFYI(1, "inode = 0x%p file flags are 0x%x for %s",
 		 inode, file->f_flags, full_path);
 
-	if (oplockEnabled)
+	if (enable_oplocks)
 		oplock = REQ_OPLOCK;
 	else
 		oplock = 0;
@@ -495,7 +495,7 @@ static int cifs_reopen_file(struct cifsFileInfo *pCifsFile, bool can_flush)
 	cFYI(1, "inode = 0x%p file flags 0x%x for %s",
 		 inode, pCifsFile->f_flags, full_path);
 
-	if (oplockEnabled)
+	if (enable_oplocks)
 		oplock = REQ_OPLOCK;
 	else
 		oplock = 0;