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Commit d134b00b authored by Kay Sievers's avatar Kay Sievers Committed by Jens Axboe
Browse files

loop: add BLK_DEV_LOOP_MIN_COUNT=%i to allow distros 0 pre-allocated loop devices 



Instead of unconditionally creating a fixed number of dead loop
devices which need to be investigated by storage handling services,
even when they are never used, we allow distros start with 0
loop devices and have losetup(8) and similar switch to the dynamic
/dev/loop-control interface instead of searching /dev/loop%i for free
devices.

Signed-off-by: default avatarKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 770fe30a

Documentation/kernel-parameters.txt

+6 −3
Original line number Diff line number Diff line
@@ -1340,9 +1340,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			it is equivalent to "nosmp", which also disables

			the IO APIC.



	max_loop=	[LOOP] Maximum number of loopback devices that can

			be mounted

			Format: <1-256>

	max_loop=	[LOOP] The number of loop block devices that get

	(loop.max_loop)	unconditionally pre-created at init time. The default

			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead

			of statically allocating a predefined number, loop

			devices can be requested on-demand with the

			/dev/loop-control interface.



	mcatest=	[IA-64]

drivers/block/Kconfig

+15 −0
Original line number Diff line number Diff line
@@ -256,6 +256,21 @@ config BLK_DEV_LOOP 


	  Most users will answer N here.



config BLK_DEV_LOOP_MIN_COUNT

	int "Number of loop devices to pre-create at init time"

	depends on BLK_DEV_LOOP

	default 8

	help

	  Static number of loop devices to be unconditionally pre-created

	  at init time.



	  This default value can be overwritten on the kernel command

	  line or with module-parameter loop.max_loop.



	  The historic default is 8. If a late 2011 version of losetup(8)

	  is used, it can be set to 0, since needed loop devices can be

	  dynamically allocated with the /dev/loop-control interface.



config BLK_DEV_CRYPTOLOOP

	tristate "Cryptoloop Support"

	select CRYPTO

drivers/block/loop.c

+10 −17
Original line number Diff line number Diff line
@@ -1793,21 +1793,6 @@ static int __init loop_init(void) 
	struct loop_device *lo;

	int err;



	/*

	 * loop module now has a feature to instantiate underlying device

	 * structure on-demand, provided that there is an access dev node.

	 * However, this will not work well with user space tool that doesn't

	 * know about such "feature".  In order to not break any existing

	 * tool, we do the following:

	 *

	 * (1) if max_loop is specified, create that many upfront, and this

	 *     also becomes a hard limit.

	 * (2) if max_loop is not specified, create 8 loop device on module

	 *     load, user can further extend loop device by create dev node

	 *     themselves and have kernel automatically instantiate actual

	 *     device on-demand.

	 */



	err = misc_register(&loop_misc);

	if (err < 0)

		return err;
@@ -1833,11 +1818,19 @@ static int __init loop_init(void) 
	if (max_loop > 1UL << (MINORBITS - part_shift))

		return -EINVAL;



	/*

	 * If max_loop is specified, create that many devices upfront.

	 * This also becomes a hard limit. If max_loop is not specified,

	 * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module

	 * init time. Loop devices can be requested on-demand with the

	 * /dev/loop-control interface, or be instantiated by accessing

	 * a 'dead' device node.

	 */

	if (max_loop) {

		nr = max_loop;

		range = max_loop << part_shift;

	} else {

		nr = 8;

		nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT;

		range = 1UL << MINORBITS;

	}
@@ -1847,7 +1840,7 @@ static int __init loop_init(void) 
	blk_register_region(MKDEV(LOOP_MAJOR, 0), range,

				  THIS_MODULE, loop_probe, NULL, NULL);



	/* pre-create number devices of devices given by config or max_loop */

	/* pre-create number of devices given by config or max_loop */

	mutex_lock(&loop_index_mutex);

	for (i = 0; i < nr; i++)

		loop_add(&lo, i);