From 24ce9a20260713e86377cfa78fb8699335759f4f Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 23 Jun 2016 16:37:12 -0600 Subject: [PATCH] block: Give nonzero result to blk_get_max_transfer_length() 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 Reviewed-by: Kevin Wolf Reviewed-by: Fam Zheng Signed-off-by: Kevin Wolf --- 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 34500e6080..1fb070b4e4 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 fb43bbaa46..dd94cd4dc7 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -384,7 +384,7 @@ 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) { @@ -394,7 +394,6 @@ 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 75e227de95..0cb8568f1f 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);