block/ataflop: add registration bool before calling del_gendisk()

The ataflop assumes del_gendisk() is safe to call, this is only
true because add_disk() does not return a failure, but that will
change soon. And so, before we get to adding error handling for
that case, let's make sure we keep track of which disks actually
get registered. Then we use this to only call del_gendisk for them.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20210927220302.1073499-13-mcgrof@kernel.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/ataflop.c

@@ -299,6 +299,7 @@ static struct atari_floppy_struct {
 				   disk change detection) */
 	int flags;		/* flags */
 	struct gendisk *disk[NUM_DISK_MINORS];
+	bool registered[NUM_DISK_MINORS];
 	int ref;
 	int type;
 	struct blk_mq_tag_set tag_set;
@@ -2001,8 +2002,10 @@ static void ataflop_probe(dev_t dev)
 		return;
 	mutex_lock(&ataflop_probe_lock);
 	if (!unit[drive].disk[type]) {
-		if (ataflop_alloc_disk(drive, type) == 0)
+		if (ataflop_alloc_disk(drive, type) == 0) {
 			add_disk(unit[drive].disk[type]);
+			unit[drive].registered[type] = true;
+		}
 	}
 	mutex_unlock(&ataflop_probe_lock);
 }
@@ -2066,6 +2069,7 @@ static int __init atari_floppy_init (void)
 		unit[i].track = -1;
 		unit[i].flags = 0;
 		add_disk(unit[i].disk[0]);
+		unit[i].registered[0] = true;
 	}
 
 	printk(KERN_INFO "Atari floppy driver: max. %cD, %strack buffering\n",
@@ -2134,7 +2138,8 @@ static void __exit atari_floppy_exit(void)
 		for (type = 0; type < NUM_DISK_MINORS; type++) {
 			if (!unit[i].disk[type])
 				continue;
-			del_gendisk(unit[i].disk[type]);
+			if (unit[i].registered[type])
+				del_gendisk(unit[i].disk[type]);
 			blk_cleanup_disk(unit[i].disk[type]);
 		}
 		blk_mq_free_tag_set(&unit[i].tag_set);