diff options
| author | Christoph Hellwig <hch@lst.de> | 2009-09-17 19:57:42 +0200 |
|---|---|---|
| committer | Rusty Russell <rusty@rustcorp.com.au> | 2009-09-23 22:26:36 +0930 |
| commit | f1b0ef062602713c2c7cfa12362d5d90ed01c5f6 (patch) | |
| tree | 30a130141b7c4b69ff20d134734acd40f1ee0960 /include/linux/virtio_blk.h | |
| parent | 3ca4f5ca73057a617f9444a91022d7127041970a (diff) | |
virtio_blk: add support for cache flush
Recent qemu has added a VIRTIO_BLK_F_FLUSH flag to advertise that the
virtual disk has a volatile write cache that needs to be flushed. In case
we see this feature implement tell the Linux block layer about the fact
and use the new VIRTIO_BLK_T_FLUSH to flush the cache when required. This
allows for an correct and simple implementation of write barriers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'include/linux/virtio_blk.h')
| -rw-r--r-- | include/linux/virtio_blk.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/include/linux/virtio_blk.h b/include/linux/virtio_blk.h index 25fbabfa90d4..15cb666581d7 100644 --- a/include/linux/virtio_blk.h +++ b/include/linux/virtio_blk.h @@ -14,6 +14,7 @@ #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_IDENTIFY 8 /* ATA IDENTIFY supported */ +#define VIRTIO_BLK_F_FLUSH 9 /* Cache flush command support */ #define VIRTIO_BLK_ID_BYTES (sizeof(__u16[256])) /* IDENTIFY DATA */ @@ -35,6 +36,17 @@ struct virtio_blk_config { __u8 identify[VIRTIO_BLK_ID_BYTES]; } __attribute__((packed)); +/* + * Command types + * + * Usage is a bit tricky as some bits are used as flags and some are not. + * + * Rules: + * VIRTIO_BLK_T_OUT may be combined with VIRTIO_BLK_T_SCSI_CMD or + * VIRTIO_BLK_T_BARRIER. VIRTIO_BLK_T_FLUSH is a command of its own + * and may not be combined with any of the other flags. + */ + /* These two define direction. */ #define VIRTIO_BLK_T_IN 0 #define VIRTIO_BLK_T_OUT 1 @@ -42,6 +54,9 @@ struct virtio_blk_config { /* This bit says it's a scsi command, not an actual read or write. */ #define VIRTIO_BLK_T_SCSI_CMD 2 +/* Cache flush command */ +#define VIRTIO_BLK_T_FLUSH 4 + /* Barrier before this op. */ #define VIRTIO_BLK_T_BARRIER 0x80000000 |