[PATCH v20 12/12] null_blk: add support for copy offload

[Nitesh Shetty <nj.shetty@samsung.com>]

Implementation is based on existing read and write infrastructure.
copy_max_bytes: A new configfs and module parameter is introduced, which
can be used to set hardware/driver supported maximum copy limit.
Only request based queue mode will support for copy offload.
Added tracefs support to copy IO tracing.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Suggested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
---
 Documentation/block/null_blk.rst  |   5 ++
 drivers/block/null_blk/main.c     | 102 +++++++++++++++++++++++++++++-
 drivers/block/null_blk/null_blk.h |   1 +
 drivers/block/null_blk/trace.h    |  23 +++++++
 4 files changed, 128 insertions(+), 3 deletions(-)

diff --git a/Documentation/block/null_blk.rst b/Documentation/block/null_blk.rst
index 4dd78f24d10a..6153e02fcf13 100644
--- a/Documentation/block/null_blk.rst
+++ b/Documentation/block/null_blk.rst
@@ -149,3 +149,8 @@ zone_size=[MB]: Default: 256
 zone_nr_conv=[nr_conv]: Default: 0
   The number of conventional zones to create when block device is zoned.  If
   zone_nr_conv >= nr_zones, it will be reduced to nr_zones - 1.
+
+copy_max_bytes=[size in bytes]: Default: COPY_MAX_BYTES
+  A module and configfs parameter which can be used to set hardware/driver
+  supported maximum copy offload limit.
+  COPY_MAX_BYTES(=128MB at present) is defined in fs.h
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index b33b9ebfebd2..dcfbd5275414 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -172,6 +172,10 @@ static int g_max_sectors;
 module_param_named(max_sectors, g_max_sectors, int, 0444);
 MODULE_PARM_DESC(max_sectors, "Maximum size of a command (in 512B sectors)");
 
+static unsigned long g_copy_max_bytes = BLK_COPY_MAX_BYTES;
+module_param_named(copy_max_bytes, g_copy_max_bytes, ulong, 0444);
+MODULE_PARM_DESC(copy_max_bytes, "Maximum size of a copy command (in bytes)");
+
 static unsigned int nr_devices = 1;
 module_param(nr_devices, uint, 0444);
 MODULE_PARM_DESC(nr_devices, "Number of devices to register");
@@ -433,6 +437,7 @@ NULLB_DEVICE_ATTR(home_node, uint, NULL);
 NULLB_DEVICE_ATTR(queue_mode, uint, NULL);
 NULLB_DEVICE_ATTR(blocksize, uint, NULL);
 NULLB_DEVICE_ATTR(max_sectors, uint, NULL);
+NULLB_DEVICE_ATTR(copy_max_bytes, uint, NULL);
 NULLB_DEVICE_ATTR(irqmode, uint, NULL);
 NULLB_DEVICE_ATTR(hw_queue_depth, uint, NULL);
 NULLB_DEVICE_ATTR(index, uint, NULL);
@@ -577,6 +582,7 @@ static struct configfs_attribute *nullb_device_attrs[] = {
 	&nullb_device_attr_queue_mode,
 	&nullb_device_attr_blocksize,
 	&nullb_device_attr_max_sectors,
+	&nullb_device_attr_copy_max_bytes,
 	&nullb_device_attr_irqmode,
 	&nullb_device_attr_hw_queue_depth,
 	&nullb_device_attr_index,
@@ -687,7 +693,7 @@ static ssize_t memb_group_features_show(struct config_item *item, char *page)
 			"shared_tags,size,submit_queues,use_per_node_hctx,"
 			"virt_boundary,zoned,zone_capacity,zone_max_active,"
 			"zone_max_open,zone_nr_conv,zone_offline,zone_readonly,"
-			"zone_size,zone_append_max_sectors\n");
+			"zone_size,zone_append_max_sectors,copy_max_bytes\n");
 }
 
 CONFIGFS_ATTR_RO(memb_group_, features);
@@ -753,6 +759,7 @@ static struct nullb_device *null_alloc_dev(void)
 	dev->queue_mode = g_queue_mode;
 	dev->blocksize = g_bs;
 	dev->max_sectors = g_max_sectors;
+	dev->copy_max_bytes = g_copy_max_bytes;
 	dev->irqmode = g_irqmode;
 	dev->hw_queue_depth = g_hw_queue_depth;
 	dev->blocking = g_blocking;
@@ -1221,6 +1228,81 @@ static int null_transfer(struct nullb *nullb, struct page *page,
 	return err;
 }
 
+static inline int nullb_setup_copy(struct nullb *nullb, struct request *req,
+				   bool is_fua)
+{
+	sector_t sector_in = 0, sector_out = 0;
+	loff_t offset_in, offset_out;
+	void *in, *out;
+	ssize_t chunk, rem = 0;
+	struct bio *bio;
+	struct nullb_page *t_page_in, *t_page_out;
+	u16 seg = 1;
+	int status = -EIO;
+
+	if (blk_rq_nr_phys_segments(req) != BLK_COPY_MAX_SEGMENTS)
+		return status;
+
+	/*
+	 * First bio contains information about destination and last bio
+	 * contains information about source.
+	 */
+	__rq_for_each_bio(bio, req) {
+		if (seg == blk_rq_nr_phys_segments(req)) {
+			sector_in = bio->bi_iter.bi_sector;
+			if (rem != bio->bi_iter.bi_size)
+				return status;
+		} else {
+			sector_out = bio->bi_iter.bi_sector;
+			rem = bio->bi_iter.bi_size;
+		}
+		seg++;
+	}
+
+	trace_nullb_copy_op(req, sector_out << SECTOR_SHIFT,
+			    sector_in << SECTOR_SHIFT, rem);
+
+	spin_lock_irq(&nullb->lock);
+	while (rem > 0) {
+		chunk = min_t(size_t, nullb->dev->blocksize, rem);
+		offset_in = (sector_in & SECTOR_MASK) << SECTOR_SHIFT;
+		offset_out = (sector_out & SECTOR_MASK) << SECTOR_SHIFT;
+
+		if (null_cache_active(nullb) && !is_fua)
+			null_make_cache_space(nullb, PAGE_SIZE);
+
+		t_page_in = null_lookup_page(nullb, sector_in, false,
+					     !null_cache_active(nullb));
+		if (!t_page_in)
+			goto err;
+		t_page_out = null_insert_page(nullb, sector_out,
+					      !null_cache_active(nullb) ||
+					      is_fua);
+		if (!t_page_out)
+			goto err;
+
+		in = kmap_local_page(t_page_in->page);
+		out = kmap_local_page(t_page_out->page);
+
+		memcpy(out + offset_out, in + offset_in, chunk);
+		kunmap_local(out);
+		kunmap_local(in);
+		__set_bit(sector_out & SECTOR_MASK, t_page_out->bitmap);
+
+		if (is_fua)
+			null_free_sector(nullb, sector_out, true);
+
+		rem -= chunk;
+		sector_in += chunk >> SECTOR_SHIFT;
+		sector_out += chunk >> SECTOR_SHIFT;
+	}
+
+	status = 0;
+err:
+	spin_unlock_irq(&nullb->lock);
+	return status;
+}
+
 static blk_status_t null_handle_rq(struct nullb_cmd *cmd)
 {
 	struct request *rq = blk_mq_rq_from_pdu(cmd);
@@ -1230,13 +1312,16 @@ static blk_status_t null_handle_rq(struct nullb_cmd *cmd)
 	sector_t sector = blk_rq_pos(rq);
 	struct req_iterator iter;
 	struct bio_vec bvec;
+	bool fua = rq->cmd_flags & REQ_FUA;
+
+	if (op_is_copy(req_op(rq)))
+		return nullb_setup_copy(nullb, rq, fua);
 
 	spin_lock_irq(&nullb->lock);
 	rq_for_each_segment(bvec, rq, iter) {
 		len = bvec.bv_len;
 		err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset,
-				     op_is_write(req_op(rq)), sector,
-				     rq->cmd_flags & REQ_FUA);
+				     op_is_write(req_op(rq)), sector, fua);
 		if (err)
 			break;
 		sector += len >> SECTOR_SHIFT;
@@ -1721,6 +1806,12 @@ static void null_config_discard(struct nullb *nullb, struct queue_limits *lim)
 	lim->max_hw_discard_sectors = UINT_MAX >> 9;
 }
 
+static void null_config_copy(struct nullb *nullb, struct queue_limits *lim)
+{
+	lim->max_copy_hw_sectors = nullb->dev->copy_max_bytes >> SECTOR_SHIFT;
+	lim->max_copy_sectors = nullb->dev->copy_max_bytes >> SECTOR_SHIFT;
+}
+
 static const struct block_device_operations null_ops = {
 	.owner		= THIS_MODULE,
 	.report_zones	= null_report_zones,
@@ -1843,6 +1934,9 @@ static int null_validate_conf(struct nullb_device *dev)
 		return -EINVAL;
 	}
 
+	if (dev->queue_mode == NULL_Q_BIO)
+		dev->copy_max_bytes = 0;
+
 	return 0;
 }
 
@@ -1909,6 +2003,8 @@ static int null_add_dev(struct nullb_device *dev)
 	if (dev->virt_boundary)
 		lim.virt_boundary_mask = PAGE_SIZE - 1;
 	null_config_discard(nullb, &lim);
+	null_config_copy(nullb, &lim);
+
 	if (dev->zoned) {
 		rv = null_init_zoned_dev(dev, &lim);
 		if (rv)
diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index 3234e6c85eed..c588729c17bd 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -91,6 +91,7 @@ struct nullb_device {
 	unsigned int queue_mode; /* block interface */
 	unsigned int blocksize; /* block size */
 	unsigned int max_sectors; /* Max sectors per command */
+	unsigned long copy_max_bytes; /* Max copy offload length in bytes */
 	unsigned int irqmode; /* IRQ completion handler */
 	unsigned int hw_queue_depth; /* queue depth */
 	unsigned int index; /* index of the disk, only valid with a disk */
diff --git a/drivers/block/null_blk/trace.h b/drivers/block/null_blk/trace.h
index f9eadac6b22f..cda1a2249978 100644
--- a/drivers/block/null_blk/trace.h
+++ b/drivers/block/null_blk/trace.h
@@ -76,6 +76,29 @@ TRACE_EVENT(nullb_report_zones,
 );
 #endif /* CONFIG_BLK_DEV_ZONED */
 
+TRACE_EVENT(nullb_copy_op,
+		TP_PROTO(struct request *req,
+			 sector_t dst, sector_t src, size_t len),
+		TP_ARGS(req, dst, src, len),
+		TP_STRUCT__entry(
+				 __array(char, disk, DISK_NAME_LEN)
+				 __field(enum req_op, op)
+				 __field(sector_t, dst)
+				 __field(sector_t, src)
+				 __field(size_t, len)
+		),
+		TP_fast_assign(
+			       __entry->op = req_op(req);
+			       __assign_disk_name(__entry->disk, req->q->disk);
+			       __entry->dst = dst;
+			       __entry->src = src;
+			       __entry->len = len;
+		),
+		TP_printk("%s req=%-15s: dst=%llu, src=%llu, len=%lu",
+			  __print_disk_name(__entry->disk),
+			  blk_op_str(__entry->op),
+			  __entry->dst, __entry->src, __entry->len)
+);
 #endif /* _TRACE_NULLB_H */
 
 #undef TRACE_INCLUDE_PATH
-- 
2.17.1