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Re: [Qemu-devel] [PATCH v3 08/22] block: Give nonzero result to blk_get_
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH v3 08/22] block: Give nonzero result to blk_get_max_transfer_length() |
Date: |
Fri, 24 Jun 2016 13:24:04 +0800 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
On Thu, 06/23 16:37, Eric Blake wrote:
> Making all callers special-case 0 as unlimited is awkward,
> and we DO have a hard maximum of BDRV_REQUEST_MAX_SECTORS given
> our current block layer API limits.
>
> In the case of scsi, this means that we now always advertise a
> limit to the guest, even in cases where the underlying layers
> previously use 0 for no inherent limit beyond the block layer.
>
> Signed-off-by: Eric Blake <address@hidden>
> Reviewed-by: Kevin Wolf <address@hidden>
>
> ---
> v3: rebase to scsi limits fix
> v2: new patch
> ---
> block/block-backend.c | 7 ++++---
> hw/block/virtio-blk.c | 3 +--
> hw/scsi/scsi-generic.c | 12 ++++++------
> 3 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/block/block-backend.c b/block/block-backend.c
> index 34500e6..1fb070b 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c
> @@ -1303,15 +1303,16 @@ int blk_get_flags(BlockBackend *blk)
> }
> }
>
> +/* Returns the maximum transfer length, in sectors; guaranteed nonzero */
> int blk_get_max_transfer_length(BlockBackend *blk)
> {
> BlockDriverState *bs = blk_bs(blk);
> + int max = 0;
>
> if (bs) {
> - return bs->bl.max_transfer_length;
> - } else {
> - return 0;
> + max = bs->bl.max_transfer_length;
> }
> + return MIN_NON_ZERO(max, BDRV_REQUEST_MAX_SECTORS);
> }
>
> int blk_get_max_iov(BlockBackend *blk)
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index 284e646..1d2792e 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -382,7 +382,7 @@ static int multireq_compare(const void *a, const void *b)
> void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb)
> {
> int i = 0, start = 0, num_reqs = 0, niov = 0, nb_sectors = 0;
> - int max_xfer_len = 0;
> + int max_xfer_len;
> int64_t sector_num = 0;
>
> if (mrb->num_reqs == 1) {
> @@ -392,7 +392,6 @@ void virtio_blk_submit_multireq(BlockBackend *blk,
> MultiReqBuffer *mrb)
> }
>
> max_xfer_len = blk_get_max_transfer_length(mrb->reqs[0]->dev->blk);
> - max_xfer_len = MIN_NON_ZERO(max_xfer_len, BDRV_REQUEST_MAX_SECTORS);
>
> qsort(mrb->reqs, mrb->num_reqs, sizeof(*mrb->reqs),
> &multireq_compare);
> diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
> index 75e227d..0cb8568 100644
> --- a/hw/scsi/scsi-generic.c
> +++ b/hw/scsi/scsi-generic.c
> @@ -227,12 +227,12 @@ static void scsi_read_complete(void * opaque, int ret)
> r->req.cmd.buf[2] == 0xb0) {
> uint32_t max_xfer_len = blk_get_max_transfer_length(s->conf.blk) /
> (s->blocksize / BDRV_SECTOR_SIZE);
> - if (max_xfer_len) {
> - stl_be_p(&r->buf[8], max_xfer_len);
> - /* Also take care of the opt xfer len. */
> - if (ldl_be_p(&r->buf[12]) > max_xfer_len) {
> - stl_be_p(&r->buf[12], max_xfer_len);
> - }
> +
> + assert(max_xfer_len);
> + stl_be_p(&r->buf[8], max_xfer_len);
> + /* Also take care of the opt xfer len. */
> + if (ldl_be_p(&r->buf[12]) > max_xfer_len) {
> + stl_be_p(&r->buf[12], max_xfer_len);
> }
> }
> scsi_req_data(&r->req, len);
> --
> 2.5.5
>
Reviewed-by: Fam Zheng <address@hidden>
- [Qemu-devel] [PATCH v3 00/22] Byte-based block limits, Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 04/22] nbd: Allow larger requests, Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 09/22] blkdebug: Set request_alignment during .bdrv_refresh_limits(), Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 08/22] block: Give nonzero result to blk_get_max_transfer_length(), Eric Blake, 2016/06/23
- Re: [Qemu-devel] [PATCH v3 08/22] block: Give nonzero result to blk_get_max_transfer_length(),
Fam Zheng <=
- [Qemu-devel] [PATCH v3 02/22] block: Document supported flags during bdrv_aligned_preadv(), Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 06/22] iscsi: Advertise realistic limits to block layer, Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 05/22] nbd: Advertise realistic limits to block layer, Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 07/22] scsi: Advertise limits by blocksize, not 512, Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 01/22] block: Tighter assertions on bdrv_aligned_pwritev(), Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 13/22] block: Set request_alignment during .bdrv_refresh_limits(), Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 10/22] iscsi: Set request_alignment during .bdrv_refresh_limits(), Eric Blake, 2016/06/23
- [Qemu-devel] [PATCH v3 15/22] block: Switch transfer length bounds to byte-based, Eric Blake, 2016/06/23