Commit 69740c8b authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Rusty Russell
Browse files

virtio_blk: add block topology support 



Allow reading various alignment values from the config page.  This
allows the guest to much better align I/O requests depending on the
storage topology.

Note that the formats for the config values appear a bit messed up,
but we follow the formats used by ATA and SCSI so they are expected in
the storage world.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent d57ed95d

drivers/block/virtio_blk.c

+46 −15
Original line number Diff line number Diff line
@@ -243,10 +243,12 @@ static int index_to_minor(int index) 
static int __devinit virtblk_probe(struct virtio_device *vdev)

{

	struct virtio_blk *vblk;

	struct request_queue *q;

	int err;

	u64 cap;

	u32 v;

	u32 blk_size, sg_elems;

	u32 v, blk_size, sg_elems, opt_io_size;

	u16 min_io_size;

	u8 physical_block_exp, alignment_offset;



	if (index_to_minor(index) >= 1 << MINORBITS)

		return -ENOSPC;
@@ -293,13 +295,13 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) 
		goto out_mempool;

	}



	vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);

	if (!vblk->disk->queue) {

	q = vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);

	if (!q) {

		err = -ENOMEM;

		goto out_put_disk;

	}



	vblk->disk->queue->queuedata = vblk;

	q->queuedata = vblk;



	if (index < 26) {

		sprintf(vblk->disk->disk_name, "vd%c", 'a' + index % 26);
@@ -323,10 +325,10 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) 


	/* If barriers are supported, tell block layer that queue is ordered */

	if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH))

		blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_DRAIN_FLUSH,

		blk_queue_ordered(q, QUEUE_ORDERED_DRAIN_FLUSH,

				  virtblk_prepare_flush);

	else if (virtio_has_feature(vdev, VIRTIO_BLK_F_BARRIER))

		blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_TAG, NULL);

		blk_queue_ordered(q, QUEUE_ORDERED_TAG, NULL);



	/* If disk is read-only in the host, the guest should obey */

	if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))
@@ -345,14 +347,14 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) 
	set_capacity(vblk->disk, cap);



	/* We can handle whatever the host told us to handle. */

	blk_queue_max_phys_segments(vblk->disk->queue, vblk->sg_elems-2);

	blk_queue_max_hw_segments(vblk->disk->queue, vblk->sg_elems-2);

	blk_queue_max_phys_segments(q, vblk->sg_elems-2);

	blk_queue_max_hw_segments(q, vblk->sg_elems-2);



	/* No need to bounce any requests */

	blk_queue_bounce_limit(vblk->disk->queue, BLK_BOUNCE_ANY);

	blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);



	/* No real sector limit. */

	blk_queue_max_sectors(vblk->disk->queue, -1U);

	blk_queue_max_sectors(q, -1U);



	/* Host can optionally specify maximum segment size and number of

	 * segments. */
@@ -360,16 +362,45 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) 
				offsetof(struct virtio_blk_config, size_max),

				&v);

	if (!err)

		blk_queue_max_segment_size(vblk->disk->queue, v);

		blk_queue_max_segment_size(q, v);

	else

		blk_queue_max_segment_size(vblk->disk->queue, -1U);

		blk_queue_max_segment_size(q, -1U);



	/* Host can optionally specify the block size of the device */

	err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,

				offsetof(struct virtio_blk_config, blk_size),

				&blk_size);

	if (!err)

		blk_queue_logical_block_size(vblk->disk->queue, blk_size);

		blk_queue_logical_block_size(q, blk_size);

	else

		blk_size = queue_logical_block_size(q);



	/* Use topology information if available */

	err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,

			offsetof(struct virtio_blk_config, physical_block_exp),

			&physical_block_exp);

	if (!err && physical_block_exp)

		blk_queue_physical_block_size(q,

				blk_size * (1 << physical_block_exp));



	err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,

			offsetof(struct virtio_blk_config, alignment_offset),

			&alignment_offset);

	if (!err && alignment_offset)

		blk_queue_alignment_offset(q, blk_size * alignment_offset);



	err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,

			offsetof(struct virtio_blk_config, min_io_size),

			&min_io_size);

	if (!err && min_io_size)

		blk_queue_io_min(q, blk_size * min_io_size);



	err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,

			offsetof(struct virtio_blk_config, opt_io_size),

			&opt_io_size);

	if (!err && opt_io_size)

		blk_queue_io_opt(q, blk_size * opt_io_size);





	add_disk(vblk->disk);

	return 0;
@@ -412,7 +443,7 @@ static struct virtio_device_id id_table[] = { 
static unsigned int features[] = {

	VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX,

	VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,

	VIRTIO_BLK_F_SCSI, VIRTIO_BLK_F_FLUSH

	VIRTIO_BLK_F_SCSI, VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY

};



/*

include/linux/virtio_blk.h

+13 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#define VIRTIO_BLK_F_BLK_SIZE	6	/* Block size of disk is available*/

#define VIRTIO_BLK_F_SCSI	7	/* Supports scsi command passthru */

#define VIRTIO_BLK_F_FLUSH	9	/* Cache flush command support */

#define VIRTIO_BLK_F_TOPOLOGY	10	/* Topology information is available */



struct virtio_blk_config {

	/* The capacity (in 512-byte sectors). */
@@ -29,8 +30,20 @@ struct virtio_blk_config { 
		__u8 heads;

		__u8 sectors;

	} geometry;



	/* block size of device (if VIRTIO_BLK_F_BLK_SIZE) */

	__u32 blk_size;



	/* the next 4 entries are guarded by VIRTIO_BLK_F_TOPOLOGY  */

	/* exponent for physical block per logical block. */

	__u8 physical_block_exp;

	/* alignment offset in logical blocks. */

	__u8 alignment_offset;

	/* minimum I/O size without performance penalty in logical blocks. */

	__u16 min_io_size;

	/* optimal sustained I/O size in logical blocks. */

	__u32 opt_io_size;



} __attribute__((packed));



/*

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