Don't allow enqueueing a request when not
enough free descriptors are available.
While here, also clarify some other
vq_desc_tail_idx code.
Change-Id: Ibcec2e31b2f609f2fd71f2426ce1a91728ed82f6
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/378154
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
8bd15fa161