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virtio_blk: add block topology support

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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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Christoph Hellwig
2010-02-24 14:22:25 -06:00
committed by Rusty Russell
parent d57ed95da4
commit 69740c8ba8
2 changed files with 59 additions and 15 deletions
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13
include/linux/virtio_blk.h
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@@ -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));
/*