[PATCH] SCSI tape cdev fixes for 2.6.2-rc1

The patch at the end of this message fixes the following problems:

- cdev allocation moved outside st_dev_arr_lock, prevents the debugging
error messages reported by Mike and Mike
- cdev_unmap() added before cdev_del(), prevents oops (and kernel data
corruption) in case someone tries to use a device after removing the
module
- better error handling for failures in cdev allocation

As far as I am concerned, the patch is tested but testing by others might
be useful :-)

drivers/scsi/st.c

@@ -9,7 +9,7 @@
    Steve Hirsch, Andreas Koppenh"ofer, Michael Leodolter, Eyal Lebedinsky,
    Michael Schaefer, J"org Weule, and Eric Youngdale.
 
-   Copyright 1992 - 2003 Kai Makisara
+   Copyright 1992 - 2004 Kai Makisara
    email Kai.Makisara@kolumbus.fi
 
    Some small formal changes - aeb, 950809
@@ -17,7 +17,7 @@
    Last modified: 18-JAN-1998 Richard Gooch <rgooch@atnf.csiro.au> Devfs support
  */
 
-static char *verstr = "20031228";
+static char *verstr = "20040122";
 
 #include <linux/module.h>
 
@@ -3846,27 +3846,53 @@ static int st_probe(struct device *dev)
 		STm->default_compression = ST_DONT_TOUCH;
 		STm->default_blksize = (-1);	/* No forced size */
 		STm->default_density = (-1);	/* No forced density */
+	}
+
+	for (i = 0; i < ST_NBR_PARTITIONS; i++) {
+		STps = &(tpnt->ps[i]);
+		STps->rw = ST_IDLE;
+		STps->eof = ST_NOEOF;
+		STps->at_sm = 0;
+		STps->last_block_valid = FALSE;
+		STps->drv_block = (-1);
+		STps->drv_file = (-1);
+	}
+
+	tpnt->current_mode = 0;
+	tpnt->modes[0].defined = TRUE;
 
+	tpnt->density_changed = tpnt->compression_changed =
+	    tpnt->blksize_changed = FALSE;
+	init_MUTEX(&tpnt->lock);
+
+	st_nr_dev++;
+	write_unlock(&st_dev_arr_lock);
+
+	for (mode = 0; mode < ST_NBR_MODES; ++mode) {
+		STm = &(tpnt->modes[mode]);
 		for (j=0; j < 2; j++) {
 			cdev = cdev_alloc();
 			if (!cdev) {
 				printk(KERN_ERR
-				       "st: out of memory. Device not attached.\n");
-				goto out_put_disk;
+				       "st%d: out of memory. Device not attached.\n",
+				       dev_num);
+				goto out_free_tape;
 			}
 			snprintf(cdev->kobj.name, KOBJ_NAME_LEN, "%sm%d%s", disk->disk_name,
-				 i, j ? "n" : "");
+				 mode, j ? "n" : "");
 			cdev->owner = THIS_MODULE;
 			cdev->ops = &st_fops;
-			STm->cdevs[j] = cdev;
 
-			error = cdev_add(STm->cdevs[j],
-					 MKDEV(SCSI_TAPE_MAJOR, TAPE_MINOR(dev_num, i, j)),
+			error = cdev_add(cdev,
+					 MKDEV(SCSI_TAPE_MAJOR, TAPE_MINOR(dev_num, mode, j)),
 					 1);
 			if (error) {
 				printk(KERN_ERR "st%d: Can't add %s-rewind mode %d\n",
-				       dev_num, j ? "non" : "auto", i);
+				       dev_num, j ? "non" : "auto", mode);
+				printk(KERN_ERR "st%d: Device not attached.\n", dev_num);
+				goto out_free_tape;
 			}
+			STm->cdevs[j] = cdev;
 
 			error = sysfs_create_link(&STm->cdevs[j]->kobj, &SDp->sdev_gendev.kobj,
 						  "device");
@@ -3884,35 +3910,15 @@ static int st_probe(struct device *dev)
 		       dev_num);
 	}
 
-	for (i = 0; i < ST_NBR_PARTITIONS; i++) {
-		STps = &(tpnt->ps[i]);
-		STps->rw = ST_IDLE;
-		STps->eof = ST_NOEOF;
-		STps->at_sm = 0;
-		STps->last_block_valid = FALSE;
-		STps->drv_block = (-1);
-		STps->drv_file = (-1);
-	}
-
-	tpnt->current_mode = 0;
-	tpnt->modes[0].defined = TRUE;
-
-	tpnt->density_changed = tpnt->compression_changed =
-	    tpnt->blksize_changed = FALSE;
-	init_MUTEX(&tpnt->lock);
-
-	st_nr_dev++;
-	write_unlock(&st_dev_arr_lock);
-
 	for (mode = 0; mode < ST_NBR_MODES; ++mode) {
-	    /*  Rewind entry  */
-	    devfs_mk_cdev(MKDEV(SCSI_TAPE_MAJOR, dev_num + (mode << 5)),
-				S_IFCHR | S_IRUGO | S_IWUGO,
-				"%s/mt%s", SDp->devfs_name, st_formats[mode]);
-	    /*  No-rewind entry  */
-	    devfs_mk_cdev(MKDEV(SCSI_TAPE_MAJOR, dev_num + (mode << 5) + 128),
-				S_IFCHR | S_IRUGO | S_IWUGO,
-				"%s/mt%sn", SDp->devfs_name, st_formats[mode]);
+		/*  Rewind entry  */
+		devfs_mk_cdev(MKDEV(SCSI_TAPE_MAJOR, dev_num + (mode << 5)),
+			      S_IFCHR | S_IRUGO | S_IWUGO,
+			      "%s/mt%s", SDp->devfs_name, st_formats[mode]);
+		/*  No-rewind entry  */
+		devfs_mk_cdev(MKDEV(SCSI_TAPE_MAJOR, dev_num + (mode << 5) + 128),
+			      S_IFCHR | S_IRUGO | S_IWUGO,
+			      "%s/mt%sn", SDp->devfs_name, st_formats[mode]);
 	}
 	disk->number = devfs_register_tape(SDp->devfs_name);
 
@@ -3924,18 +3930,30 @@ static int st_probe(struct device *dev)
 
 	return 0;
 
+out_free_tape:
+	for (mode=0; mode < ST_NBR_MODES; mode++) {
+		STm = &(tpnt->modes[mode]);
+		for (j=0; j < 2; j++) {
+			if (STm->cdevs[j]) {
+				if (cdev == STm->cdevs[j])
+					cdev = NULL;
+				sysfs_remove_link(&STm->cdevs[j]->kobj, "device");
+				cdev_unmap(MKDEV(SCSI_TAPE_MAJOR,
+						 TAPE_MINOR(dev_num, mode, j)), 1);
+				cdev_del(STm->cdevs[j]);
+			}
+		}
+	}
+	if (cdev)
+		kobject_put(&cdev->kobj);
+	write_lock(&st_dev_arr_lock);
+	scsi_tapes[dev_num] = NULL;
+	st_nr_dev--;
+	write_unlock(&st_dev_arr_lock);
 out_put_disk:
 	put_disk(disk);
-	if (tpnt) {
-		for (i=0; i < ST_NBR_MODES; i++) {
-			STm = &(tpnt->modes[i]);
-			if (STm->cdevs[0])
-				kobject_put(&STm->cdevs[0]->kobj);
-			if (STm->cdevs[1])
-				kobject_put(&STm->cdevs[1]->kobj);
-		}
+	if (tpnt)
 		kfree(tpnt);
-	}
 out_buffer_free:
 	kfree(buffer);
 out:
@@ -3964,6 +3982,8 @@ static int st_remove(struct device *dev)
 				for (j=0; j < 2; j++) {
 					sysfs_remove_link(&tpnt->modes[mode].cdevs[j]->kobj,
 							  "device");
+					cdev_unmap(MKDEV(SCSI_TAPE_MAJOR,
+							 TAPE_MINOR(i, mode, j)), 1);
 					cdev_del(tpnt->modes[mode].cdevs[j]);
 					tpnt->modes[mode].cdevs[j] = NULL;
 				}