loop: export module parameters
Export 'max_loop' and 'max_part' parameters to sysfs so user can know
that how many devices are allowed and how many partitions are supported.
If 'max_loop' is 0, there is no restriction on the number of loop devices.
User can create/use the devices as many as minor numbers available. If
'max_part' is 0, it means simply the device doesn't support partitioning.
Also note that 'max_part' can be adjusted to power of 2 minus 1 form if
needed. User should check this value after the module loading if he/she
want to use that number correctly (i.e. fdisk, mknod, etc.).
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c59a672..76c8da7 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1540,9 +1540,9 @@
* 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);
@@ -1688,9 +1688,20 @@
*/
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;