diff mbox series

[V4,1/8] null_blk: allow REQ_OP_WRITE_ZEROES

Message ID 20221129232813.37968-2-kch@nvidia.com (mailing list archive)
State New, archived
Headers show
Series null_blk: allow REQ_OP_WRITE_ZEROES and cleanup | expand

Commit Message

Chaitanya Kulkarni Nov. 29, 2022, 11:28 p.m. UTC 
Add a helper function to enable the REQ_OP_WRITE_ZEROES operations
when null_blk.

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     | 59 ++++++++++++++++++++++++++++++-
 drivers/block/null_blk/null_blk.h |  1 +
 2 files changed, 59 insertions(+), 1 deletion(-)

Comments

Shinichiro Kawasaki Nov. 30, 2022, 7:59 a.m. UTC | #1 
On Nov 29, 2022 / 15:28, Chaitanya Kulkarni wrote:
> Add a helper function to enable the REQ_OP_WRITE_ZEROES operations
> when null_blk.
> 
> 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>

This motivation sounds good. I tried this patch. With a quick test it looks
working good for me. Please find minor comments in line.

[...]

> +static void null_zero_sector(struct nullb_device *d, sector_t sect,
> +			     sector_t nr_sects, bool cache)
> +{
> +	struct radix_tree_root *root = cache ? &d->cache : &d->data;
> +	struct nullb_page *t_page;
> +	unsigned int offset;
> +	void *dest;
> +
> +	t_page = radix_tree_lookup(root, sect >> PAGE_SECTORS_SHIFT);
> +	if (!t_page)
> +		return;
> +
> +	offset = (sect & SECTOR_MASK) << SECTOR_SHIFT;
> +	dest = kmap_atomic(t_page->page);
> +	memset(dest + offset, 0, SECTOR_SIZE * nr_sects);
> +	kunmap_atomic(dest);
> +}

Did you consider to call null_lookup_page() for __null_lookup_page() from
null_zero_sector()? It may simplify this function a bit.

> +
>  static struct nullb_page *null_radix_tree_insert(struct nullb *nullb, u64 idx,
>  	struct nullb_page *t_page, bool is_cache)
>  {
> @@ -1186,6 +1211,27 @@ blk_status_t null_handle_discard(struct nullb_device *dev,
>  	return BLK_STS_OK;
>  }
>  
> +static blk_status_t null_handle_write_zeroes(struct nullb_device *dev,
> +					     sector_t sector, sector_t nr_sectors)
> +{
> +	unsigned int bytes_left = nr_sectors << 9;
> +	struct nullb *nullb = dev->nullb;
> +	size_t curr_bytes;
> +
> +	spin_lock_irq(&nullb->lock);
> +	while (bytes_left > 0) {
> +		curr_bytes = min_t(size_t, bytes_left, nullb->dev->blocksize);
> +		nr_sectors = curr_bytes >> SECTOR_SHIFT;
> +		null_zero_sector(nullb->dev, sector, nr_sectors, false);
> +		if (null_cache_active(nullb))
> +			null_zero_sector(nullb->dev, sector, nr_sectors, true);
> +		sector += nr_sectors;
> +		bytes_left -= curr_bytes;
> +	}
> +	spin_unlock_irq(&nullb->lock);
> +	return BLK_STS_OK;
> +}
> +
>  static int null_handle_flush(struct nullb *nullb)
>  {
>  	int err;
> @@ -1352,6 +1398,9 @@ static inline blk_status_t null_handle_memory_backed(struct nullb_cmd *cmd,
>  	if (op == REQ_OP_DISCARD)
>  		return null_handle_discard(dev, sector, nr_sectors);
>  
> +	if (op == REQ_OP_WRITE_ZEROES)
> +		return null_handle_write_zeroes(dev, sector, nr_sectors);
> +
>  	if (dev->queue_mode == NULL_Q_BIO)
>  		err = null_handle_bio(cmd);
>  	else
> @@ -1800,6 +1849,13 @@ 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);

Just comment: this value UINT_MAX >> 9 sounds a bit weird, but probably ok. This
value was introduced by commit 306eb6b4ad4f ("nullb: support discard") to call
blk_queue_max_discard_sectors(). I guess you chose the same value for write
zeroes.

> +}
> +
>  static const struct block_device_operations null_bio_ops = {
>  	.owner		= THIS_MODULE,
>  	.submit_bio	= null_submit_bio,
> @@ -2111,6 +2167,7 @@ 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
>
Chaitanya Kulkarni Nov. 30, 2022, 11:29 p.m. UTC | #2 
>> Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
> 
> This motivation sounds good. I tried this patch. With a quick test it looks
> working good for me. Please find minor comments in line.
> 
> [...]
> 
>> +static void null_zero_sector(struct nullb_device *d, sector_t sect,
>> +			     sector_t nr_sects, bool cache)
>> +{
>> +	struct radix_tree_root *root = cache ? &d->cache : &d->data;
>> +	struct nullb_page *t_page;
>> +	unsigned int offset;
>> +	void *dest;
>> +
>> +	t_page = radix_tree_lookup(root, sect >> PAGE_SECTORS_SHIFT);
>> +	if (!t_page)
>> +		return;
>> +
>> +	offset = (sect & SECTOR_MASK) << SECTOR_SHIFT;
>> +	dest = kmap_atomic(t_page->page);
>> +	memset(dest + offset, 0, SECTOR_SIZE * nr_sects);
>> +	kunmap_atomic(dest);
>> +}
> 
> Did you consider to call null_lookup_page() for __null_lookup_page() from
> null_zero_sector()? It may simplify this function a bit.
> 

I found this clear and easy than going over call chain when
debugging.

>> +
>>   static struct nullb_page *null_radix_tree_insert(struct nullb *nullb, u64 idx,

[...]

>>   
>> +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);
> 
> Just comment: this value UINT_MAX >> 9 sounds a bit weird, but probably ok. This
> value was introduced by commit 306eb6b4ad4f ("nullb: support discard") to call
> blk_queue_max_discard_sectors(). I guess you chose the same value for write
> zeroes.
> 

Yes indeed, plz have a look end patches to allow user to set this value.

-ck
Shinichiro Kawasaki Dec. 1, 2022, 1:21 a.m. UTC | #3 
On Nov 30, 2022 / 23:29, Chaitanya Kulkarni wrote:
> >> Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
> > 
> > This motivation sounds good. I tried this patch. With a quick test it looks
> > working good for me. Please find minor comments in line.
> > 
> > [...]
> > 
> >> +static void null_zero_sector(struct nullb_device *d, sector_t sect,
> >> +			     sector_t nr_sects, bool cache)
> >> +{
> >> +	struct radix_tree_root *root = cache ? &d->cache : &d->data;
> >> +	struct nullb_page *t_page;
> >> +	unsigned int offset;
> >> +	void *dest;
> >> +
> >> +	t_page = radix_tree_lookup(root, sect >> PAGE_SECTORS_SHIFT);
> >> +	if (!t_page)
> >> +		return;
> >> +
> >> +	offset = (sect & SECTOR_MASK) << SECTOR_SHIFT;
> >> +	dest = kmap_atomic(t_page->page);
> >> +	memset(dest + offset, 0, SECTOR_SIZE * nr_sects);
> >> +	kunmap_atomic(dest);
> >> +}
> > 
> > Did you consider to call null_lookup_page() for __null_lookup_page() from
> > null_zero_sector()? It may simplify this function a bit.
> > 
> 
> I found this clear and easy than going over call chain when
> debugging.

Okay, then the patch looks good to me :)

Reviewed-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
diff mbox series

Patch

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 1f154f92f4c2..2d592b4eb815 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)");
@@ -416,6 +420,7 @@  NULLB_DEVICE_ATTR(blocking, bool, NULL);
 NULLB_DEVICE_ATTR(use_per_node_hctx, bool, NULL);
 NULLB_DEVICE_ATTR(memory_backed, bool, NULL);
 NULLB_DEVICE_ATTR(discard, bool, NULL);
+NULLB_DEVICE_ATTR(write_zeroes, bool, NULL);
 NULLB_DEVICE_ATTR(mbps, uint, NULL);
 NULLB_DEVICE_ATTR(cache_size, ulong, NULL);
 NULLB_DEVICE_ATTR(zoned, bool, NULL);
@@ -540,6 +545,7 @@  static struct configfs_attribute *nullb_device_attrs[] = {
 	&nullb_device_attr_power,
 	&nullb_device_attr_memory_backed,
 	&nullb_device_attr_discard,
+	&nullb_device_attr_write_zeroes,
 	&nullb_device_attr_mbps,
 	&nullb_device_attr_cache_size,
 	&nullb_device_attr_badblocks,
@@ -614,7 +620,7 @@  static ssize_t memb_group_features_show(struct config_item *item, char *page)
 			"poll_queues,power,queue_mode,shared_tag_bitmap,size,"
 			"submit_queues,use_per_node_hctx,virt_boundary,zoned,"
 			"zone_capacity,zone_max_active,zone_max_open,"
-			"zone_nr_conv,zone_size\n");
+			"zone_nr_conv,zone_size,write_zeroes\n");
 }
 
 CONFIGFS_ATTR_RO(memb_group_, features);
@@ -678,6 +684,7 @@  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;
@@ -870,6 +877,24 @@  static void null_free_sector(struct nullb *nullb, sector_t sector,
 	}
 }
 
+static void null_zero_sector(struct nullb_device *d, sector_t sect,
+			     sector_t nr_sects, bool cache)
+{
+	struct radix_tree_root *root = cache ? &d->cache : &d->data;
+	struct nullb_page *t_page;
+	unsigned int offset;
+	void *dest;
+
+	t_page = radix_tree_lookup(root, sect >> PAGE_SECTORS_SHIFT);
+	if (!t_page)
+		return;
+
+	offset = (sect & SECTOR_MASK) << SECTOR_SHIFT;
+	dest = kmap_atomic(t_page->page);
+	memset(dest + offset, 0, SECTOR_SIZE * nr_sects);
+	kunmap_atomic(dest);
+}
+
 static struct nullb_page *null_radix_tree_insert(struct nullb *nullb, u64 idx,
 	struct nullb_page *t_page, bool is_cache)
 {
@@ -1186,6 +1211,27 @@  blk_status_t null_handle_discard(struct nullb_device *dev,
 	return BLK_STS_OK;
 }
 
+static blk_status_t null_handle_write_zeroes(struct nullb_device *dev,
+					     sector_t sector, sector_t nr_sectors)
+{
+	unsigned int bytes_left = nr_sectors << 9;
+	struct nullb *nullb = dev->nullb;
+	size_t curr_bytes;
+
+	spin_lock_irq(&nullb->lock);
+	while (bytes_left > 0) {
+		curr_bytes = min_t(size_t, bytes_left, nullb->dev->blocksize);
+		nr_sectors = curr_bytes >> SECTOR_SHIFT;
+		null_zero_sector(nullb->dev, sector, nr_sectors, false);
+		if (null_cache_active(nullb))
+			null_zero_sector(nullb->dev, sector, nr_sectors, true);
+		sector += nr_sectors;
+		bytes_left -= curr_bytes;
+	}
+	spin_unlock_irq(&nullb->lock);
+	return BLK_STS_OK;
+}
+
 static int null_handle_flush(struct nullb *nullb)
 {
 	int err;
@@ -1352,6 +1398,9 @@  static inline blk_status_t null_handle_memory_backed(struct nullb_cmd *cmd,
 	if (op == REQ_OP_DISCARD)
 		return null_handle_discard(dev, sector, nr_sectors);
 
+	if (op == REQ_OP_WRITE_ZEROES)
+		return null_handle_write_zeroes(dev, sector, nr_sectors);
+
 	if (dev->queue_mode == NULL_Q_BIO)
 		err = null_handle_bio(cmd);
 	else
@@ -1800,6 +1849,13 @@  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 +2167,7 @@  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 */