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authorKay Sievers <kay.sievers@vrfy.org>2011-07-31 22:08:04 +0200
committerJens Axboe <jaxboe@fusionio.com>2011-07-31 22:08:04 +0200
commitd134b00b9acca3fb054d7c88a5f5d562ecbb42d1 (patch)
treeccc63647ec8a551289f26866ec86091e44266bad /drivers
parent770fe30a46a12b6fb6b63fbe1737654d28e84844 (diff)
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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: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/block/Kconfig15
-rw-r--r--drivers/block/loop.c27
2 files changed, 25 insertions, 17 deletions
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 717d6e4e18d..57212c5235e 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -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
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 5c9edf94487..3defc52f060 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -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);