[PATCH RFC 3/8] virtio_blk: Add support for provision requests

[Sarthak Kukreti <sarthakkukreti@xxxxxxxxxxxx>]

From: Sarthak Kukreti <sarthakkukreti@xxxxxxxxxxxx>

Adds support for provision requests. Provision requests act like
the inverse of discards.

Signed-off-by: Sarthak Kukreti <sarthakkukreti@xxxxxxxxxxxx>
---
 drivers/block/virtio_blk.c      | 48 +++++++++++++++++++++++++++++++++
 include/uapi/linux/virtio_blk.h |  9 +++++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 30255fcaf181..eacc2bffe1d1 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -178,6 +178,39 @@ static int virtblk_setup_discard_write_zeroes(struct request *req, bool unmap)
 	return 0;
 }
 
+static int virtblk_setup_provision(struct request *req)
+{
+	unsigned short segments = blk_rq_nr_discard_segments(req);
+	unsigned short n = 0;
+
+	struct virtio_blk_discard_write_zeroes *range;
+	struct bio *bio;
+	u32 flags = 0;
+
+	range = kmalloc_array(segments, sizeof(*range), GFP_ATOMIC);
+	if (!range)
+		return -ENOMEM;
+
+	__rq_for_each_bio(bio, req) {
+		u64 sector = bio->bi_iter.bi_sector;
+		u32 num_sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT;
+
+		range[n].flags = cpu_to_le32(flags);
+		range[n].num_sectors = cpu_to_le32(num_sectors);
+		range[n].sector = cpu_to_le64(sector);
+		n++;
+	}
+
+	WARN_ON_ONCE(n != segments);
+
+	req->special_vec.bv_page = virt_to_page(range);
+	req->special_vec.bv_offset = offset_in_page(range);
+	req->special_vec.bv_len = sizeof(*range) * segments;
+	req->rq_flags |= RQF_SPECIAL_PAYLOAD;
+
+	return 0;
+}
+
 static void virtblk_unmap_data(struct request *req, struct virtblk_req *vbr)
 {
 	if (blk_rq_nr_phys_segments(req))
@@ -243,6 +276,9 @@ static blk_status_t virtblk_setup_cmd(struct virtio_device *vdev,
 	case REQ_OP_DRV_IN:
 		type = VIRTIO_BLK_T_GET_ID;
 		break;
+	case REQ_OP_PROVISION:
+		type = VIRTIO_BLK_T_PROVISION;
+		break;
 	default:
 		WARN_ON_ONCE(1);
 		return BLK_STS_IOERR;
@@ -256,6 +292,11 @@ static blk_status_t virtblk_setup_cmd(struct virtio_device *vdev,
 			return BLK_STS_RESOURCE;
 	}
 
+	if (type == VIRTIO_BLK_T_PROVISION) {
+		if (virtblk_setup_provision(req))
+			return BLK_STS_RESOURCE;
+	}
+
 	return 0;
 }
 
@@ -1075,6 +1116,12 @@ static int virtblk_probe(struct virtio_device *vdev)
 		blk_queue_max_write_zeroes_sectors(q, v ? v : UINT_MAX);
 	}
 
+	if (virtio_has_feature(vdev, VIRTIO_BLK_F_PROVISION)) {
+		virtio_cread(vdev, struct virtio_blk_config,
+			     max_provision_sectors, &v);
+		q->limits.max_provision_sectors = v ? v : UINT_MAX;
+	}
+
 	virtblk_update_capacity(vblk, false);
 	virtio_device_ready(vdev);
 
@@ -1177,6 +1224,7 @@ static unsigned int features[] = {
 	VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
 	VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
 	VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD, VIRTIO_BLK_F_WRITE_ZEROES,
+	VIRTIO_BLK_F_PROVISION,
 };
 
 static struct virtio_driver virtio_blk = {
diff --git a/include/uapi/linux/virtio_blk.h b/include/uapi/linux/virtio_blk.h
index d888f013d9ff..184f8cf6d185 100644
--- a/include/uapi/linux/virtio_blk.h
+++ b/include/uapi/linux/virtio_blk.h
@@ -40,6 +40,7 @@
 #define VIRTIO_BLK_F_MQ		12	/* support more than one vq */
 #define VIRTIO_BLK_F_DISCARD	13	/* DISCARD is supported */
 #define VIRTIO_BLK_F_WRITE_ZEROES	14	/* WRITE ZEROES is supported */
+#define VIRTIO_BLK_F_PROVISION	15	/* provision is supported */
 
 /* Legacy feature bits */
 #ifndef VIRTIO_BLK_NO_LEGACY
@@ -120,6 +121,11 @@ struct virtio_blk_config {
 	 */
 	__u8 write_zeroes_may_unmap;
 
+	/*
+	 * The maximum number of sectors in a provision request.
+	 */
+	__virtio32 max_provision_sectors;
+
 	__u8 unused1[3];
 } __attribute__((packed));
 
@@ -155,6 +161,9 @@ struct virtio_blk_config {
 /* Write zeroes command */
 #define VIRTIO_BLK_T_WRITE_ZEROES	13
 
+/* Provision command */
+#define VIRTIO_BLK_T_PROVISION	14
+
 #ifndef VIRTIO_BLK_NO_LEGACY
 /* Barrier before this op. */
 #define VIRTIO_BLK_T_BARRIER	0x80000000
-- 
2.31.0