On Wed, Mar 11, 2015 at 01:28:00PM +0300, Denis V. Lunev wrote:
> Main approach is taken from qcow2_co_readv.
>
> The patch drops coroutine lock for the duration of IO operation and
> peforms normal scatter-gather IO using standard QEMU backend.
>
> Signed-off-by: Denis V. Lunev <d...@openvz.org>
> Reviewed-by: Roman Kagan <rka...@parallels.com>
> CC: Kevin Wolf <kw...@redhat.com>
> CC: Stefan Hajnoczi <stefa...@redhat.com>
> ---
> block/parallels.c | 46 +++++++++++++++++++++++++++-------------------
> 1 file changed, 27 insertions(+), 19 deletions(-)
>
> diff --git a/block/parallels.c b/block/parallels.c
> index b469984..64b169b 100644
> --- a/block/parallels.c
> +++ b/block/parallels.c
> @@ -186,37 +186,45 @@ static int64_t coroutine_fn
> parallels_co_get_block_status(BlockDriverState *bs,
> BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID;
> }
>
> -static int parallels_read(BlockDriverState *bs, int64_t sector_num,
> - uint8_t *buf, int nb_sectors)
> +static coroutine_fn int parallels_co_readv(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 = seek_to_sector(s, sector_num);
> int n = cluster_remainder(s, sector_num, nb_sectors);
> - if (position >= 0) {
> - int ret = bdrv_read(bs->file, position, buf, n);
> + int nbytes = n << BDRV_SECTOR_BITS;
> +
> + if (position < 0) {
> + qemu_iovec_memset(qiov, bytes_done, 0, nbytes);
> + } else {
> + qemu_iovec_reset(&hd_qiov);
> + qemu_iovec_concat(&hd_qiov, qiov, bytes_done, nbytes);
> +
> + qemu_co_mutex_unlock(&s->lock);
> + ret = bdrv_co_readv(bs->file, position, n, &hd_qiov);
> + qemu_co_mutex_lock(&s->lock);
> +
> if (ret < 0) {
> - return ret;
> + goto fail;
The lock is never unlocked if the goto is taken.
> }
> - } else {
> - memset(buf, 0, n << BDRV_SECTOR_BITS);
> }
> +
> nb_sectors -= n;
> sector_num += n;
> - buf += n << BDRV_SECTOR_BITS;
> + bytes_done += nbytes;
> }
> - return 0;
> -}
> -
> -static coroutine_fn int parallels_co_read(BlockDriverState *bs, int64_t
> sector_num,
> - uint8_t *buf, int nb_sectors)
> -{
> - int ret;
> - BDRVParallelsState *s = bs->opaque;
> - qemu_co_mutex_lock(&s->lock);
> - ret = parallels_read(bs, sector_num, buf, nb_sectors);
> qemu_co_mutex_unlock(&s->lock);
> +
> +fail:
> + qemu_iovec_destroy(&hd_qiov);
> return ret;
> }
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