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virtio-blk: add volatile writecache feature 

Add a new VIRTIO_BLK_F_WCACHE feature to virtio-blk to indicate that we have
a volatile write cache that needs controlled flushing.  Implement a
VIRTIO_BLK_T_FLUSH operation to flush it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Christoph Hellwig 2009-09-04 19:02:23 +02:00 committed by Anthony Liguori
parent b0484ae464
commit aa659be3dc
2 changed files with 27 additions and 1 deletions
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24
hw/virtio-blk.c
View File

@ -130,6 +130,13 @@ static void virtio_blk_rw_complete(void *opaque, int ret)
virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
}
static void virtio_blk_flush_complete(void *opaque, int ret)
{
VirtIOBlockReq *req = opaque;
virtio_blk_req_complete(req, ret ? VIRTIO_BLK_S_IOERR : VIRTIO_BLK_S_OK);
}
static VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s)
{
VirtIOBlockReq *req = qemu_mallocz(sizeof(*req));
@ -268,6 +275,16 @@ static void do_multiwrite(BlockDriverState *bs, BlockRequest *blkreq,
}
}
static void virtio_blk_handle_flush(VirtIOBlockReq *req)
{
BlockDriverAIOCB *acb;
acb = bdrv_aio_flush(req->dev->bs, virtio_blk_flush_complete, req);
if (!acb) {
virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
}
}
static void virtio_blk_handle_write(BlockRequest *blkreq, int *num_writes,
VirtIOBlockReq *req, BlockDriverState **old_bs)
{
@ -323,7 +340,9 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
req->out = (void *)req->elem.out_sg[0].iov_base;
req->in = (void *)req->elem.in_sg[req->elem.in_num - 1].iov_base;
if (req->out->type & VIRTIO_BLK_T_SCSI_CMD) {
if (req->out->type & VIRTIO_BLK_T_FLUSH) {
virtio_blk_handle_flush(req);
} else if (req->out->type & VIRTIO_BLK_T_SCSI_CMD) {
virtio_blk_handle_scsi(req);
} else if (req->out->type & VIRTIO_BLK_T_OUT) {
qemu_iovec_init_external(&req->qiov, &req->elem.out_sg[1],
@ -417,6 +436,9 @@ static uint32_t virtio_blk_get_features(VirtIODevice *vdev)
features |= (1 << VIRTIO_BLK_F_SEG_MAX);
features |= (1 << VIRTIO_BLK_F_GEOMETRY);
if (bdrv_enable_write_cache(s->bs))
features |= (1 << VIRTIO_BLK_F_WCACHE);
#ifdef __linux__
features |= (1 << VIRTIO_BLK_F_SCSI);
#endif

4
hw/virtio-blk.h
View File

@ -31,6 +31,7 @@
#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_WCACHE 9 /* write cache enabled */
#define VIRTIO_BLK_ID_LEN 256 /* length of identify u16 array */
#define VIRTIO_BLK_ID_SN 10 /* start of char * serial# */
@ -55,6 +56,9 @@ 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
/* Flush the volatile write cache */
#define VIRTIO_BLK_T_FLUSH 4
/* Barrier before this op. */
#define VIRTIO_BLK_T_BARRIER 0x80000000