[Sheepdog] [QEMU PATCH] sheepdog: add cache flush support

[MORITA Kazutaka]

At Tue, 15 Nov 2011 17:06:52 -0500,
Christoph Hellwig wrote:
> 
> This patch implement support for writeback-style cache in the sheepdog
> protocol.  The SD_OP_FLUSH_VDI command will flush all data for the
> referenced VDI to stable storage.
> 
> XXX: we'll need to figure out if the sheep server actually support this
> command somehow.

If we increment SD_PROTO_VER, the sheep daemon should return
SD_RES_VER_MISMATCH error when opening the VDI.

Thanks,

Kazutaka

> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> 
> Index: qemu/block/sheepdog.c
> ===================================================================
> --- qemu.orig/block/sheepdog.c	2011-11-15 15:16:41.989853638 +0100
> +++ qemu/block/sheepdog.c	2011-11-15 22:58:24.516354810 +0100
> @@ -29,6 +29,7 @@
>  #define SD_OP_RELEASE_VDI    0x13
>  #define SD_OP_GET_VDI_INFO   0x14
>  #define SD_OP_READ_VDIS      0x15
> +#define SD_OP_FLUSH_VDI      0x16
>  
>  #define SD_FLAG_CMD_WRITE    0x01
>  #define SD_FLAG_CMD_COW      0x02
> @@ -261,6 +262,7 @@ typedef struct AIOReq {
>  enum AIOCBState {
>      AIOCB_WRITE_UDATA,
>      AIOCB_READ_UDATA,
> +    AIOCB_FLUSH_CACHE,
>  };
>  
>  struct SheepdogAIOCB {
> @@ -813,6 +815,9 @@ static void coroutine_fn aio_read_respon
>      acb = aio_req->aiocb;
>  
>      switch (acb->aiocb_type) {
> +    case AIOCB_FLUSH_CACHE:
> +        printf("rsp.result = %d\n", rsp.result);
> +        break;
>      case AIOCB_WRITE_UDATA:
>          if (!is_data_obj(aio_req->oid)) {
>              break;
> @@ -1084,7 +1089,11 @@ static int coroutine_fn add_aio_request(
>  
>      memset(&hdr, 0, sizeof(hdr));
>  
> -    if (aiocb_type == AIOCB_READ_UDATA) {
> +    if (aiocb_type == AIOCB_FLUSH_CACHE) {
> +        wlen = 0;
> +        hdr.opcode = SD_OP_FLUSH_VDI;
> +        hdr.flags = SD_FLAG_CMD_WRITE | flags;
> +    } else if (aiocb_type == AIOCB_READ_UDATA) {
>          wlen = 0;
>          hdr.opcode = SD_OP_READ_OBJ;
>          hdr.flags = flags;
> @@ -1771,6 +1780,31 @@ static int sd_co_readv(BlockDriverState
>      return acb->ret;
>  }
>  
> +static int sd_co_flush_to_disk(BlockDriverState *bs)
> +{
> +    BDRVSheepdogState *s = bs->opaque;
> +    SheepdogInode *inode = &s->inode;
> +    SheepdogAIOCB *acb;
> +    AIOReq *aio_req;
> +    int ret;
> +
> +    acb = sd_aio_setup(bs, NULL, 0, 0, NULL, NULL);
> +    acb->aiocb_type = AIOCB_FLUSH_CACHE;
> +    acb->aio_done_func = sd_finish_aiocb;
> +
> +    aio_req = alloc_aio_req(s, acb, inode->vdi_id, 0, 0, 0, 0, 0);
> +
> +    ret = add_aio_request(s, aio_req, NULL, 0, 0,  acb->aiocb_type);
> +    if (ret < 0) {
> +        free_aio_req(s, aio_req);
> +        qemu_aio_release(acb);
> +        return ret;
> +    }
> +
> +    qemu_coroutine_yield();
> +    return acb->ret;
> +}
> +
>  static int sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
>  {
>      BDRVSheepdogState *s = bs->opaque;
> @@ -2100,6 +2134,7 @@ BlockDriver bdrv_sheepdog = {
>  
>      .bdrv_co_readv  = sd_co_readv,
>      .bdrv_co_writev = sd_co_writev,
> +    .bdrv_co_flush_to_disk  = sd_co_flush_to_disk,
>  
>      .bdrv_snapshot_create   = sd_snapshot_create,
>      .bdrv_snapshot_goto     = sd_snapshot_goto,
> -- 
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