[PATCH 3/7] cbd: introduce cbd_channel

[Dongsheng Yang]

From: Dongsheng Yang <dongsheng.yang.linux@xxxxxxxxx>

The "cbd_channel" is the component responsible for the interaction
between the blkdev and the backend. It mainly provides the functions
"cbdc_copy_to_bio" and "cbdc_copy_from_bio".

The "cbdc_copy_to_bio" function copies data from the specified area of
the channel to the bio. Before copying, it flushes the dcache to ensure
that the data read from the channel is the latest.

The "cbdc_copy_from_bio" function copies data from the bio to the
specified area of the channel. After copying, it flushes the dcache to
ensure that other parties can see the latest data.

Signed-off-by: Dongsheng Yang <dongsheng.yang.linux@xxxxxxxxx>
---
 drivers/block/cbd/Makefile      |   2 +-
 drivers/block/cbd/cbd_channel.c | 179 ++++++++++++++++++++++++++++++++
 2 files changed, 180 insertions(+), 1 deletion(-)
 create mode 100644 drivers/block/cbd/cbd_channel.c

diff --git a/drivers/block/cbd/Makefile b/drivers/block/cbd/Makefile
index a22796bfa7db..c581ae96732b 100644
--- a/drivers/block/cbd/Makefile
+++ b/drivers/block/cbd/Makefile
@@ -1,3 +1,3 @@
-cbd-y := cbd_main.o cbd_transport.o
+cbd-y := cbd_main.o cbd_transport.o cbd_channel.o
 
 obj-$(CONFIG_BLK_DEV_CBD) += cbd.o
diff --git a/drivers/block/cbd/cbd_channel.c b/drivers/block/cbd/cbd_channel.c
new file mode 100644
index 000000000000..7253523bea3c
--- /dev/null
+++ b/drivers/block/cbd/cbd_channel.c
@@ -0,0 +1,179 @@
+#include "cbd_internal.h"
+
+static ssize_t cbd_backend_id_show(struct device *dev,
+			       struct device_attribute *attr,
+			       char *buf)
+{
+	struct cbd_channel_device *channel;
+	struct cbd_channel_info *channel_info;
+
+	channel = container_of(dev, struct cbd_channel_device, dev);
+	channel_info = channel->channel_info;
+
+	if (channel_info->backend_state == cbdc_backend_state_none)
+		return 0;
+
+	return sprintf(buf, "%u\n", channel_info->backend_id);
+}
+
+static ssize_t cbd_blkdev_id_show(struct device *dev,
+			       struct device_attribute *attr,
+			       char *buf)
+{
+	struct cbd_channel_device *channel;
+	struct cbd_channel_info *channel_info;
+
+	channel = container_of(dev, struct cbd_channel_device, dev);
+	channel_info = channel->channel_info;
+
+	if (channel_info->blkdev_state == cbdc_blkdev_state_none)
+		return 0;
+
+	return sprintf(buf, "%u\n", channel_info->blkdev_id);
+}
+
+static DEVICE_ATTR(backend_id, 0400, cbd_backend_id_show, NULL);
+static DEVICE_ATTR(blkdev_id, 0400, cbd_blkdev_id_show, NULL);
+
+static struct attribute *cbd_channel_attrs[] = {
+	&dev_attr_backend_id.attr,
+	&dev_attr_blkdev_id.attr,
+	NULL
+};
+
+static struct attribute_group cbd_channel_attr_group = {
+	.attrs = cbd_channel_attrs,
+};
+
+static const struct attribute_group *cbd_channel_attr_groups[] = {
+	&cbd_channel_attr_group,
+	NULL
+};
+
+static void cbd_channel_release(struct device *dev)
+{
+}
+
+struct device_type cbd_channel_type = {
+	.name		= "cbd_channel",
+	.groups		= cbd_channel_attr_groups,
+	.release	= cbd_channel_release,
+};
+
+struct device_type cbd_channels_type = {
+	.name		= "cbd_channels",
+	.release	= cbd_channel_release,
+};
+
+void cbdc_copy_to_bio(struct cbd_channel *channel,
+		u32 data_off, u32 data_len, struct bio *bio)
+{
+	struct bio_vec bv;
+	struct bvec_iter iter;
+	void *src, *dst;
+	u32 data_head = data_off;
+	u32 to_copy, page_off = 0;
+
+	cbdt_flush_range(channel->cbdt, channel->data + data_off, data_len);
+next:
+	bio_for_each_segment(bv, bio, iter) {
+		dst = kmap_atomic(bv.bv_page);
+		page_off = bv.bv_offset;
+again:
+		if (data_head >= CBDC_DATA_SIZE) {
+			data_head &= CBDC_DATA_MASK;
+		}
+
+		src = channel->data + data_head;
+		to_copy = min(bv.bv_offset + bv.bv_len - page_off,
+			      CBDC_DATA_SIZE - data_head);
+		memcpy_flushcache(dst + page_off, src, to_copy);
+
+		/* advance */
+		data_head += to_copy;
+		page_off += to_copy;
+
+		/* more data in this bv page */
+		if (page_off < bv.bv_offset + bv.bv_len) {
+			goto again;
+		}
+		kunmap_atomic(dst);
+		flush_dcache_page(bv.bv_page);
+	}
+
+	if (bio->bi_next) {
+		bio = bio->bi_next;
+		goto next;
+	}
+
+	return;
+}
+
+void cbdc_copy_from_bio(struct cbd_channel *channel,
+		u32 data_off, u32 data_len, struct bio *bio)
+{
+	struct bio_vec bv;
+	struct bvec_iter iter;
+	void *src, *dst;
+	u32 data_head = data_off;
+	u32 to_copy, page_off = 0;
+
+next:
+	bio_for_each_segment(bv, bio, iter) {
+		flush_dcache_page(bv.bv_page);
+
+		src = kmap_atomic(bv.bv_page);
+		page_off = bv.bv_offset;
+again:
+		if (data_head >= CBDC_DATA_SIZE) {
+			data_head &= CBDC_DATA_MASK;
+		}
+
+		dst = channel->data + data_head;
+		to_copy = min(bv.bv_offset + bv.bv_len - page_off,
+			      CBDC_DATA_SIZE - data_head);
+
+		memcpy_flushcache(dst, src + page_off, to_copy);
+
+		/* advance */
+		data_head += to_copy;
+		page_off += to_copy;
+
+		/* more data in this bv page */
+		if (page_off < bv.bv_offset + bv.bv_len) {
+			goto again;
+		}
+		kunmap_atomic(src);
+	}
+
+	if (bio->bi_next) {
+		bio = bio->bi_next;
+		goto next;
+	}
+
+	cbdt_flush_range(channel->cbdt, channel->data + data_off, data_len);
+
+	return;
+}
+
+void cbdc_flush_ctrl(struct cbd_channel *channel)
+{
+	flush_dcache_page(channel->ctrl_page);
+}
+
+void cbd_channel_init(struct cbd_channel *channel, struct cbd_transport *cbdt, u32 channel_id)
+{
+	struct cbd_channel_info *channel_info = cbdt_get_channel_info(cbdt, channel_id);
+
+	channel->cbdt = cbdt;
+	channel->channel_info = channel_info;
+	channel->channel_id = channel_id;
+	channel->cmdr = (void *)channel_info + CBDC_CMDR_OFF;
+	channel->compr = (void *)channel_info + CBDC_COMPR_OFF;
+	channel->data = (void *)channel_info + CBDC_DATA_OFF;
+	channel->data_size = CBDC_DATA_SIZE;
+	channel->ctrl_page = cbdt_page(cbdt, (void *)channel_info - (void *)cbdt->transport_info);
+
+	spin_lock_init(&channel->cmdr_lock);
+	spin_lock_init(&channel->compr_lock);
+}
-- 
2.34.1