[PATCH 3/8] null_blk: add support for write-zeroes

[Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>]

This patch adds support to execute REQ_OP_WRITE_ZEROES operations on
the null_blk device when device is not memory-backed. Just like
REQ_OP_DISCARD we add a new module parameter to enable this support.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
---
 drivers/block/null_blk_main.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 20d60b951622..65da7c2d93b9 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -198,6 +198,10 @@ static bool g_discard;
 module_param_named(discard, g_discard, bool, 0444);
 MODULE_PARM_DESC(discard, "Allow REQ_OP_DISCARD processing. Default: false");
 
+static bool g_write_zeroes;
+module_param_named(write_zeroes, g_write_zeroes, bool, 0444);
+MODULE_PARM_DESC(write_zeroes, "Allow REQ_OP_WRITE_ZEROES 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);
@@ -535,7 +539,10 @@ static struct nullb_device *null_alloc_dev(void)
 	dev->zone_size = g_zone_size;
 	dev->zone_nr_conv = g_zone_nr_conv;
 	dev->discard = g_discard;
+	dev->write_zeroes = g_write_zeroes;
 	pr_info("discard : %s\n", dev->discard ? "TRUE" : "FALSE");
+	pr_info("write-zeroes : %s\n", dev->write_zeroes ? "TRUE" : "FALSE");
+
 	return dev;
 }
 
@@ -1419,6 +1426,13 @@ static void null_config_discard(struct nullb *nullb)
 	blk_queue_flag_set(QUEUE_FLAG_DISCARD, nullb->q);
 }
 
+static void null_config_write_zeroes(struct nullb *nullb)
+{
+	if (nullb->dev->write_zeroes == false)
+		return;
+	blk_queue_max_write_zeroes_sectors(nullb->q, UINT_MAX >> SECTOR_SHIFT);
+}
+
 static int null_open(struct block_device *bdev, fmode_t mode)
 {
 	return 0;
@@ -1710,6 +1724,7 @@ static int null_add_dev(struct nullb_device *dev)
 	blk_queue_physical_block_size(nullb->q, dev->blocksize);
 
 	null_config_discard(nullb);
+	null_config_write_zeroes(nullb);
 
 	sprintf(nullb->disk_name, "nullb%d", nullb->index);
 
-- 
2.17.0