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 <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 6 insertions, 6 deletions

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);