Currently, the max_loop commandline argument can be used to specify how many loop block devices are created at init time. If it is not specified on the commandline, CONFIG_BLK_DEV_LOOP_MIN_COUNT loop block devices will be created.

The max_loop commandline argument can be used to override the value of CONFIG_BLK_DEV_LOOP_MIN_COUNT. However, when max_loop is set to 0 through the commandline, the current logic treats it as if it had not been set, and creates CONFIG_BLK_DEV_LOOP_MIN_COUNT devices anyway.

Fix this by starting max_loop off as set to CONFIG_BLK_DEV_LOOP_MIN_COUNT. This preserves the intended behavior of creating CONFIG_BLK_DEV_LOOP_MIN_COUNT loop block devices if the max_loop commandline parameter is not specified, and allowing max_loop to be respected for all values, including 0.

This allows environments that can create all of their required loop block devices on demand to not have to unnecessarily preallocate loop block devices.

Fixes: 732850827450 ("remove artificial software max_loop limit") Cc: stable@vger.kernel.org Cc: Ken Chen kenchen@google.com Signed-off-by: Isaac J. Manjarres isaacmanjarres@google.com --- drivers/block/loop.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-)

This is a resend because I misspelled the address for stable@vger.kernel.org the first time.

--Isaac

diff --git a/drivers/block/loop.c b/drivers/block/loop.c index ad92192c7d61..d12d3d171ec4 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1773,7 +1773,16 @@ static const struct block_device_operations lo_fops = { /* * And now the modules code and kernel interface. */ -static int max_loop; + +/* + * 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. + */ +static int max_loop = CONFIG_BLK_DEV_LOOP_MIN_COUNT; module_param(max_loop, int, 0444); MODULE_PARM_DESC(max_loop, "Maximum number of loop devices"); module_param(max_part, int, 0444); @@ -2181,7 +2190,7 @@ MODULE_ALIAS("devname:loop-control");

static int __init loop_init(void) { - int i, nr; + int i; int err;

part_shift = 0; @@ -2209,19 +2218,6 @@ static int __init loop_init(void) goto err_out; }

- /* - * 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; - else - nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT; - err = misc_register(&loop_misc); if (err < 0) goto err_out; @@ -2233,7 +2229,7 @@ static int __init loop_init(void) }

/* pre-create number of devices given by config or max_loop */ - for (i = 0; i < nr; i++) + for (i = 0; i < max_loop; i++) loop_add(i);

printk(KERN_INFO "loop: module loaded\n");