virtio_blk: allow read-only disks

Hello Rusty,

sometimes it is useful to share a disk (e.g. usr). To avoid file system
corruption, the disk should be mounted read-only in that case. This patch
adds a new feature flag, that allows the host to specify, if the disk should
be considered read-only.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/virtio_blk.h b/include/linux/virtio_blk.h
index d4695a3356d0..b80919fad0ef 100644
--- a/include/linux/virtio_blk.h
+++ b/include/linux/virtio_blk.h
@@ -10,6 +10,7 @@
 #define VIRTIO_BLK_F_SIZE_MAX   1       /* Indicates maximum segment size */
 #define VIRTIO_BLK_F_SEG_MAX    2       /* Indicates maximum # of segments */
 #define VIRTIO_BLK_F_GEOMETRY   4       /* Legacy geometry available  */
+#define VIRTIO_BLK_F_RO         5       /* Disk is read-only */
 
 struct virtio_blk_config
 {