[PATCH 1/8] null_blk: add module parameter for REQ_OP_DISCARD

[Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>]

This patch adds a module parameter to configure the REQ_OP_DISCARD
handling support when null_blk module is not memory-backed. This support
is useful in the various scenarios such as examining REQ_OP_DISCARD path
tests, blktrace and discard with priorities.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
---
 drivers/block/null_blk_main.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 99328ded60d1..20d60b951622 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -3,6 +3,7 @@
  * Add configfs and memory store: Kyungchan Koh <kkc6196@xxxxxx> and
  * Shaohua Li <shli@xxxxxx>
  */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 #include <linux/module.h>
 
 #include <linux/moduleparam.h>
@@ -193,6 +194,10 @@ static unsigned int g_zone_nr_conv;
 module_param_named(zone_nr_conv, g_zone_nr_conv, uint, 0444);
 MODULE_PARM_DESC(zone_nr_conv, "Number of conventional zones when block device is zoned. Default: 0");
 
+static bool g_discard;
+module_param_named(discard, g_discard, bool, 0444);
+MODULE_PARM_DESC(discard, "Allow REQ_OP_DISCARD processing. Default: false");
+
 static struct nullb_device *null_alloc_dev(void);
 static void null_free_dev(struct nullb_device *dev);
 static void null_del_dev(struct nullb *nullb);
@@ -529,6 +534,8 @@ static struct nullb_device *null_alloc_dev(void)
 	dev->zoned = g_zoned;
 	dev->zone_size = g_zone_size;
 	dev->zone_nr_conv = g_zone_nr_conv;
+	dev->discard = g_discard;
+	pr_info("discard : %s\n", dev->discard ? "TRUE" : "FALSE");
 	return dev;
 }
 
-- 
2.17.0