Re: [Qemu-devel] [PATCH V15 09/13] quorum: Add quorum_co_get_block_status.

[Kevin Wolf <kwolf@redhat.com>]

Am 03.02.2014 um 22:51 hat Benoît Canet geschrieben:
> From: Benoît Canet <benoit@irqsave.net>
> 
> Signed-off-by: Benoit Canet <benoit@irqsave.net>
> Reviewed-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/quorum.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
> 
> diff --git a/block/quorum.c b/block/quorum.c
> index cef4424..677a96d 100644
> --- a/block/quorum.c
> +++ b/block/quorum.c
> @@ -619,6 +619,56 @@ static void quorum_invalidate_cache(BlockDriverState *bs)
>      }
>  }
>  
> +static int64_t coroutine_fn quorum_co_get_block_status(BlockDriverState *bs,
> +                                                       int64_t sector_num,
> +                                                       int nb_sectors,
> +                                                       int *pnum)
> +{
> +    BDRVQuorumState *s = bs->opaque;
> +    QuorumVoteVersion *winner = NULL;
> +    QuorumVotes result_votes, num_votes;
> +    QuorumVoteValue result_value, num_value;
> +    int i, num;
> +    int64_t result = 0;
> +
> +    QLIST_INIT(&result_votes.vote_list);
> +    QLIST_INIT(&num_votes.vote_list);
> +    result_votes.compare = quorum_64bits_compare;
> +    num_votes.compare = quorum_64bits_compare;
> +
> +    for (i = 0; i < s->total; i++) {
> +        result = bdrv_get_block_status(s->bs[i], sector_num, nb_sectors, &num);
> +        /* skip failed requests */
> +        if (result < 0) {
> +            continue;
> +        }
> +        result_value.l = result & BDRV_BLOCK_DATA;
> +        num_value.l = num;
> +        quorum_count_vote(&result_votes, &result_value, i);
> +        quorum_count_vote(&num_votes, &num_value, i);
> +    }

This doesn't work. bdrv_get_block_status() doesn't guarantee that it
returns all consecutive blocks with the same status. You need to call it
in a loop here, or change bdrv_get_block_status() so that it loops
itself.

> +    winner = quorum_get_vote_winner(&result_votes);
> +    if (winner->vote_count < s->threshold) {
> +        result = -EIO;
> +        goto free_exit;
> +    }
> +    result = winner->value.l;
> +
> +    winner = quorum_get_vote_winner(&num_votes);
> +    if (winner->vote_count < s->threshold) {
> +        result = -EIO;
> +        goto free_exit;
> +    }
> +    *pnum = winner->value.l;

You can take the status from one group of devices and the number of
blocks that share this state from another group?!

> +
> +free_exit:
> +    quorum_free_vote_list(&result_votes);
> +    quorum_free_vote_list(&num_votes);
> +
> +    return result;
> +}
> +
>  static BlockDriver bdrv_quorum = {
>      .format_name        = "quorum",
>      .protocol_name      = "quorum",
> @@ -630,6 +680,7 @@ static BlockDriver bdrv_quorum = {
>      .bdrv_aio_readv     = quorum_aio_readv,
>      .bdrv_aio_writev    = quorum_aio_writev,
>      .bdrv_invalidate_cache = quorum_invalidate_cache,
> +    .bdrv_co_get_block_status = quorum_co_get_block_status,
>  };
>  
>  static void bdrv_quorum_init(void)

Kevin