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From:   Chaitanya Kulkarni <kch@nvidia.com>
To:     <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>
CC:     <axboe@kernel.dk>, <kch@nvidia.com>,
        <damien.lemoal@opensource.wdc.com>, <johannes.thumshirn@wdc.com>,
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        <shinichiro.kawasaki@wdc.com>, <vincent.fu@samsung.com>,
        <yukuai3@huawei.com>
Subject: [PATCH 1/6] null_blk: allow write zeores on non-membacked
Date:   Tue, 4 Oct 2022 20:16:56 -0700
Message-ID: <20221005031701.79077-2-kch@nvidia.com>
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Add a helper function to enable the REQ_OP_WRITE_ZEROES operations
when null_blk is configured with the non-membacked operations.

Since write-zeroes is a non-trivial I/O operation we need this to
add a blktest so we can test the non-trivial I/O path from the
application to the block layer.

Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
---
 drivers/block/null_blk/main.c     | 13 +++++++++++++
 drivers/block/null_blk/null_blk.h |  1 +
 2 files changed, 14 insertions(+)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 1f154f92f4c2..fc3e883f7b84 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -209,6 +209,10 @@ static bool g_discard;
 module_param_named(discard, g_discard, bool, 0444);
 MODULE_PARM_DESC(discard, "Support discard operations (requires memory-backed null_blk device). Default: false");
 
+static bool g_write_zeroes;
+module_param_named(write_zeroes, g_write_zeroes, bool, 0444);
+MODULE_PARM_DESC(write_zeroes, "Support write-zeores operations. Default: false");
+
 static unsigned long g_cache_size;
 module_param_named(cache_size, g_cache_size, ulong, 0444);
 MODULE_PARM_DESC(mbps, "Cache size in MiB for memory-backed device. Default: 0 (none)");
@@ -678,6 +682,7 @@ static struct nullb_device *null_alloc_dev(void)
 	dev->blocking = g_blocking;
 	dev->memory_backed = g_memory_backed;
 	dev->discard = g_discard;
+	dev->write_zeroes = g_write_zeroes;
 	dev->cache_size = g_cache_size;
 	dev->mbps = g_mbps;
 	dev->use_per_node_hctx = g_use_per_node_hctx;
@@ -1800,6 +1805,13 @@ static void null_config_discard(struct nullb *nullb)
 	blk_queue_max_discard_sectors(nullb->q, UINT_MAX >> 9);
 }
 
+static void null_config_write_zeroes(struct nullb *nullb)
+{
+	if (!nullb->dev->write_zeroes)
+		return;
+	blk_queue_max_write_zeroes_sectors(nullb->q, UINT_MAX >> 9);
+}
+
 static const struct block_device_operations null_bio_ops = {
 	.owner		= THIS_MODULE,
 	.submit_bio	= null_submit_bio,
@@ -2111,6 +2123,7 @@ static int null_add_dev(struct nullb_device *dev)
 		blk_queue_virt_boundary(nullb->q, PAGE_SIZE - 1);
 
 	null_config_discard(nullb);
+	null_config_write_zeroes(nullb);
 
 	if (config_item_name(&dev->item)) {
 		/* Use configfs dir name as the device name */
diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index 94ff68052b1e..2c0c9c29158f 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -111,6 +111,7 @@ struct nullb_device {
 	bool power; /* power on/off the device */
 	bool memory_backed; /* if data is stored in memory */
 	bool discard; /* if support discard */
+	bool write_zeroes; /* if support write_zeroes */
 	bool zoned; /* if device is zoned */
 	bool virt_boundary; /* virtual boundary on/off for the device */
 	bool no_sched; /* no IO scheduler for the device */
-- 
2.29.0