null_blk: add 'memory_backed' module parameter

Commit Message

Akinobu Mita March 25, 2020, 3:40 p.m. UTC

Currently, the memory_backed feature is only enabled by the null block
device configured through configfs.
This adds module parameter to make device as a memory-backed block device,
and reduces a few steps required to test zonefs with zoned null block
device.

Cc: Jens Axboe <[e-mail]>
Signed-off-by: Akinobu Mita <[e-mail]>
---
 Documentation/block/null_blk.rst | 3 +++
 drivers/block/null_blk_main.c    | 5 +++++
 2 files changed, 8 insertions(+)

Patch

diff --git a/Documentation/block/null_blk.rst b/Documentation/block/null_blk.rst
index edbbab2f12f8..036970121198 100644
--- a/Documentation/block/null_blk.rst
+++ b/Documentation/block/null_blk.rst
@@ -72,6 +72,9 @@  submit_queues=[1..nr_cpus]: Default: 1
 hw_queue_depth=[0..qdepth]: Default: 64
   The hardware queue depth of the device.
 
+memory_backed=[0/1]: Default: 0
+  Device is a memory-backed or no transfer block device.
+
 Multi-queue specific parameters
 -------------------------------
 
diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 133060431dbd..1ed2ccc5960b 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -177,6 +177,10 @@  static int g_hw_queue_depth = 64;
 module_param_named(hw_queue_depth, g_hw_queue_depth, int, 0444);
 MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: 64");
 
+static bool g_memory_backed;
+module_param_named(memory_backed, g_memory_backed, bool, 0444);
+MODULE_PARM_DESC(memory_backed, "Make device as a memory-backed block device. Default: false");
+
 static bool g_use_per_node_hctx;
 module_param_named(use_per_node_hctx, g_use_per_node_hctx, bool, 0444);
 MODULE_PARM_DESC(use_per_node_hctx, "Use per-node allocation for hardware context queues. Default: false");
@@ -551,6 +555,7 @@  static struct nullb_device *null_alloc_dev(void)
 	dev->irqmode = g_irqmode;
 	dev->hw_queue_depth = g_hw_queue_depth;
 	dev->blocking = g_blocking;
+	dev->memory_backed = g_memory_backed;
 	dev->use_per_node_hctx = g_use_per_node_hctx;
 	dev->zoned = g_zoned;
 	dev->zone_size = g_zone_size;