Am 24.10.2013 um 12:06 hat Peter Lieven geschrieben:
> Reviewed-by: Eric Blake <ebl...@redhat.com>
> Signed-off-by: Peter Lieven <p...@kamp.de>
> ---
> block.c | 37 ++++++++++++++++++++++++++++++++++++-
> 1 file changed, 36 insertions(+), 1 deletion(-)
>
> diff --git a/block.c b/block.c
> index 0c0b0ac..b28dd42 100644
> --- a/block.c
> +++ b/block.c
> @@ -4234,6 +4234,11 @@ static void coroutine_fn bdrv_discard_co_entry(void
> *opaque)
> rwco->ret = bdrv_co_discard(rwco->bs, rwco->sector_num,
> rwco->nb_sectors);
> }
>
> +/* if no limit is specified in the BlockLimits use a default
> + * of 32768 512-byte sectors (16 MiB) per request.
> + */
> +#define MAX_DISCARD_DEFAULT 32768
> +
> int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors)
> {
> @@ -4255,7 +4260,37 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs,
> int64_t sector_num,
> }
>
> if (bs->drv->bdrv_co_discard) {
> - return bs->drv->bdrv_co_discard(bs, sector_num, nb_sectors);
> + int max_discard = bs->bl.max_discard ?
> + bs->bl.max_discard : MAX_DISCARD_DEFAULT;
> +
> + while (nb_sectors > 0) {
> + int ret;
> + int num = nb_sectors;
> +
> + /* align request */
> + if (bs->bl.discard_alignment &&
> + num >= bs->bl.discard_alignment &&
> + sector_num % bs->bl.discard_alignment) {
> + if (num > bs->bl.discard_alignment) {
> + num = bs->bl.discard_alignment;
> + }
> + num -= sector_num % bs->bl.discard_alignment;
> + }
> +
> + /* limit request size */
> + if (num > max_discard) {
> + num = max_discard;
> + }
> +
> + ret = bs->drv->bdrv_co_discard(bs, sector_num, num);
> + if (ret) {
> + return ret;
> + }
> +
> + sector_num += num;
> + nb_sectors -= num;
> + }
> + return 0;
> } else if (bs->drv->bdrv_aio_discard) {
> BlockDriverAIOCB *acb;
> CoroutineIOCompletion co = {
You're only optimising drivers which have a .bdrv_co_discard()
implementation, but not those with .bdrv_aio_discard(). Not very nice,
and it would have been easy to avoid this by putting the loop around the
whole if statement instead of inside the 'then' branch.
Kevin
