Re: [Qemu-devel] [PATCH 08/27] block/parallels: _co_writev callback for Parallels format

["Denis V. Lunev" <den@openvz.org>]

On 11/03/15 13:28, Denis V. Lunev wrote:
> Support write on Parallels images. The code is almost the same as one
> in the previous patch implemented scatter-gather IO for read.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> Reviewed-by: Roman Kagan <rkagan@parallels.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   block/parallels.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
>   1 file changed, 75 insertions(+), 2 deletions(-)
>
> diff --git a/block/parallels.c b/block/parallels.c
> index 306f2e3..61d7da7 100644
> --- a/block/parallels.c
> +++ b/block/parallels.c
> @@ -81,8 +81,6 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
>       ParallelsHeader ph;
>       int ret;
>   
> -    bs->read_only = 1; // no write support yet
> -
>       ret = bdrv_pread(bs->file, 0, &ph, sizeof(ph));
>       if (ret < 0) {
>           goto fail;
> @@ -166,6 +164,37 @@ static int cluster_remainder(BDRVParallelsState *s, int64_t sector_num,
>       return MIN(nb_sectors, ret);
>   }
>   
> +static int64_t allocate_cluster(BlockDriverState *bs, int64_t sector_num)
> +{
> +    BDRVParallelsState *s = bs->opaque;
> +    uint32_t idx, offset, tmp;
> +    int64_t pos;
> +    int ret;
> +
> +    idx = sector_num / s->tracks;
> +    offset = sector_num % s->tracks;
> +
> +    if (idx >= s->catalog_size) {
> +        return -EINVAL;
> +    }
> +    if (s->catalog_bitmap[idx] != 0) {
> +        return (uint64_t)s->catalog_bitmap[idx] * s->off_multiplier + offset;
> +    }
> +
> +    pos = bdrv_getlength(bs->file) >> BDRV_SECTOR_BITS;
> +    bdrv_truncate(bs->file, (pos + s->tracks) << BDRV_SECTOR_BITS);
> +    s->catalog_bitmap[idx] = pos / s->off_multiplier;
> +
> +    tmp = cpu_to_le32(s->catalog_bitmap[idx]);
> +
> +    ret = bdrv_pwrite_sync(bs->file,
> +            sizeof(ParallelsHeader) + idx * sizeof(tmp), &tmp, sizeof(tmp));
> +    if (ret < 0) {
> +        return ret;
> +    }
> +    return (uint64_t)s->catalog_bitmap[idx] * s->off_multiplier + offset;
> +}
> +
>   static int64_t coroutine_fn parallels_co_get_block_status(BlockDriverState *bs,
>           int64_t sector_num, int nb_sectors, int *pnum)
>   {
> @@ -186,6 +215,49 @@ static int64_t coroutine_fn parallels_co_get_block_status(BlockDriverState *bs,
>           BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID;
>   }
>   
> +static coroutine_fn int parallels_co_writev(BlockDriverState *bs,
> +        int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
> +{
> +    BDRVParallelsState *s = bs->opaque;
> +    uint64_t bytes_done = 0;
> +    QEMUIOVector hd_qiov;
> +    int ret = 0;
> +
> +    qemu_iovec_init(&hd_qiov, qiov->niov);
> +
> +    qemu_co_mutex_lock(&s->lock);
> +    while (nb_sectors > 0) {
> +        int64_t position = allocate_cluster(bs, sector_num);
> +        int n = cluster_remainder(s, sector_num, nb_sectors);
> +        int nbytes = n << BDRV_SECTOR_BITS;
> +
> +        if (position < 0) {
> +            ret = (int)position;
> +            break;
> +        }
> +
> +        qemu_iovec_reset(&hd_qiov);
> +        qemu_iovec_concat(&hd_qiov, qiov, bytes_done, nbytes);
> +
> +        qemu_co_mutex_unlock(&s->lock);
> +        ret = bdrv_co_writev(bs->file, position, n, &hd_qiov);
> +        qemu_co_mutex_lock(&s->lock);
> +
> +        if (ret < 0) {
> +            goto fail;
same problem with unlock as in patch 6


> +        }
> +
> +        nb_sectors -= n;
> +        sector_num += n;
> +        bytes_done += nbytes;
> +    }
> +    qemu_co_mutex_unlock(&s->lock);
> +
> +fail:
> +    qemu_iovec_destroy(&hd_qiov);
> +    return ret;
> +}
> +
>   static coroutine_fn int parallels_co_readv(BlockDriverState *bs,
>           int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
>   {
> @@ -242,6 +314,7 @@ static BlockDriver bdrv_parallels = {
>       .bdrv_close		= parallels_close,
>       .bdrv_co_get_block_status = parallels_co_get_block_status,
>       .bdrv_co_readv  = parallels_co_readv,
> +    .bdrv_co_writev = parallels_co_writev,
>   };
>   
>   static void bdrv_parallels_init(void)