1 files changed, 21 insertions, 7 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index a076a14ca72d..76c8da78212b 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1540,9 +1540,9 @@ static const struct block_device_operations lo_fops = {
  * And now the modules code and kernel interface.
  */
 static int max_loop;
-module_param(max_loop, int, 0);
+module_param(max_loop, int, S_IRUGO);
 MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
-module_param(max_part, int, 0);
+module_param(max_part, int, S_IRUGO);
 MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
@@ -1658,7 +1658,7 @@ static struct kobject *loop_probe(dev_t dev, int *part, void *data)
 	struct kobject *kobj;
 
 	mutex_lock(&loop_devices_mutex);
-	lo = loop_init_one(dev & MINORMASK);
+	lo = loop_init_one(MINOR(dev) >> part_shift);
 	kobj = lo ? get_disk(lo->lo_disk) : ERR_PTR(-ENOMEM);
 	mutex_unlock(&loop_devices_mutex);
 
@@ -1688,18 +1688,32 @@ static int __init loop_init(void)
 	 */
 
 	part_shift = 0;
-	if (max_part > 0)
+	if (max_part > 0) {
 		part_shift = fls(max_part);
 
+		/*
+		 * Adjust max_part according to part_shift as it is exported
+		 * to user space so that user can decide correct minor number
+		 * if [s]he want to create more devices.
+		 *
+		 * Note that -1 is required because partition 0 is reserved
+		 * for the whole disk.
+		 */
+		max_part = (1UL << part_shift) - 1;
+	}
+
+	if ((1UL << part_shift) > DISK_MAX_PARTS)
+		return -EINVAL;
+
 	if (max_loop > 1UL << (MINORBITS - part_shift))
 		return -EINVAL;
 
 	if (max_loop) {
 		nr = max_loop;
-		range = max_loop;
+		range = max_loop << part_shift;
 	} else {
 		nr = 8;
-		range = 1UL << (MINORBITS - part_shift);
+		range = 1UL << MINORBITS;
 	}
 
 	if (register_blkdev(LOOP_MAJOR, "loop"))
@@ -1738,7 +1752,7 @@ static void __exit loop_exit(void)
 	unsigned long range;
 	struct loop_device *lo, *next;
 
-	range = max_loop ? max_loop :  1UL << (MINORBITS - part_shift);
+	range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
 
 	list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
 		loop_del_one(lo);