virtio_blk: check for hardsector size from host
Currently virtio_blk assumes a 512 byte hard sector size. This can cause
trouble / performance issues if the backing has a different block size
(like a file on an ext3 file system formatted with 4k block size or a dasd).
Lets add a feature flag that tells the guest to use a different hard sector
size than 512 byte.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index dd7ea20..4225109 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -196,6 +196,7 @@
int err;
u64 cap;
u32 v;
+ u32 blk_size;
if (index_to_minor(index) >= 1 << MINORBITS)
return -ENOSPC;
@@ -290,6 +291,13 @@
if (!err)
blk_queue_max_hw_segments(vblk->disk->queue, v);
+ /* 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_hardsect_size(vblk->disk->queue, blk_size);
+
add_disk(vblk->disk);
return 0;
@@ -330,7 +338,7 @@
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_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
};
static struct virtio_driver virtio_blk = {