[PATCH] reduce stack usage in cdrom/optcd.c

This changes/fixes the optcd.c stack reduction patch from last week.

Alan and Jens objected to the kmalloc() in cdromread(), suggesting that
the read buffer should be allocated one time and held onto, so this
patch does that.

drivers/cdrom/optcd.c

@@ -1598,19 +1598,17 @@ static int cdromsubchnl(unsigned long arg)
 }
 
 
+static struct gendisk *optcd_disk;
+
+
 static int cdromread(unsigned long arg, int blocksize, int cmd)
 {
-	int status, ret = 0;
+	int status;
 	struct cdrom_msf msf;
-	char *buf;
 
 	if (copy_from_user(&msf, (void *) arg, sizeof msf))
 		return -EFAULT;
 
-	buf = kmalloc(CD_FRAMESIZE_RAWER, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
 	bin2bcd(&msf);
 	msf.cdmsf_min1 = 0;
 	msf.cdmsf_sec1 = 0;
@@ -1619,19 +1617,15 @@ static int cdromread(unsigned long arg, int blocksize, int cmd)
 
 	DEBUG((DEBUG_VFS, "read cmd status 0x%x", status));
 
-	if (!sleep_flag_low(FL_DTEN, SLEEP_TIMEOUT)) {
-		ret = -EIO;
-		goto cdr_free;
-	}
+	if (!sleep_flag_low(FL_DTEN, SLEEP_TIMEOUT))
+		return -EIO;
 
-	fetch_data(buf, blocksize);
+	fetch_data(optcd_disk->private_data, blocksize);
 
-	if (copy_to_user((void *)arg, &buf, blocksize))
-		ret = -EFAULT;
+	if (copy_to_user((void *)arg, optcd_disk->private_data, blocksize))
+		return -EFAULT;
 
-cdr_free:
-	kfree(buf);
-	return ret;
+	return 0;
 }
 
 
@@ -1857,6 +1851,14 @@ static int opt_open(struct inode *ip, struct file *fp)
 
 	if (!open_count && state == S_IDLE) {
 		int status;
+		char *buf;
+
+		buf = kmalloc(CD_FRAMESIZE_RAWER, GFP_KERNEL);
+		if (!buf) {
+			printk(KERN_INFO "optcd: cannot allocate read buffer\n");
+			return -ENOMEM;
+		}
+		optcd_disk->private_data = buf;		/* save read buffer */
 
 		toc_uptodate = 0;
 		opt_invalidate_buffers();
@@ -1922,6 +1924,7 @@ static int opt_release(struct inode *ip, struct file *fp)
 			status = exec_cmd(COMOPEN);
 			DEBUG((DEBUG_VFS, "exec_cmd COMOPEN: %02x", -status));
 		}
+		kfree(optcd_disk->private_data);
 		del_timer(&delay_timer);
 		del_timer(&req_timer);
 	}
@@ -2010,8 +2013,6 @@ __setup("optcd=", optcd_setup);
 
 #endif /* MODULE */
 
-static struct gendisk *optcd_disk;
-
 /* Test for presence of drive and initialize it. Called at boot time
    or during module initialisation. */
 static int __init optcd_init(void)