ublk: Make ublks_max configurable

We are converting tcmu applications to ublk, but have systems with up
to 1k devices. This patch allows us to configure the ublks_max from
userspace with the ublks_max modparam.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20231012150600.6198-3-michael.christie@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index ba7c6f9ee136eec2c45bbb59bdfe44a03420e59e..b0bbda08ad453c782a79dc0eeb020b6d4e02ee07 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -2940,7 +2940,22 @@ static void __exit ublk_exit(void)
 module_init(ublk_init);
 module_exit(ublk_exit);
 
-module_param(ublks_max, int, 0444);
+static int ublk_set_max_ublks(const char *buf, const struct kernel_param *kp)
+{
+       return param_set_uint_minmax(buf, kp, 0, UBLK_MAX_UBLKS);
+}
+
+static int ublk_get_max_ublks(char *buf, const struct kernel_param *kp)
+{
+       return sysfs_emit(buf, "%u\n", ublks_max);
+}
+
+static const struct kernel_param_ops ublk_max_ublks_ops = {
+       .set = ublk_set_max_ublks,
+       .get = ublk_get_max_ublks,
+};
+
+module_param_cb(ublks_max, &ublk_max_ublks_ops, &ublks_max, 0644);
 MODULE_PARM_DESC(ublks_max, "max number of ublk devices allowed to add(default: 64)");
 
 MODULE_AUTHOR("Ming Lei <ming.lei@redhat.com>");