On Tue, Feb 07, 2017 at 01:34:54PM -0500, Keith Busch wrote: > On Tue, Feb 07, 2017 at 05:46:58PM +0100, Christoph Hellwig wrote: > > @@ -1233,6 +1243,8 @@ static void nvme_set_queue_limits(struct nvme_ctrl > > *ctrl, > > if (ctrl->vwc & NVME_CTRL_VWC_PRESENT) > > vwc = true; > > blk_queue_write_cache(q, vwc, vwc); > > + blk_queue_max_discard_segments(q, > > + PAGE_SIZE / sizeof(struct nvme_dsm_range)); > > We need to use ctrl->page_size rather than PAGE_SIZE.
We need the PAGE_SIZE upper bound because the "special" bvec only allows a single page payload. I can't find any indication that the DSM command is limited to a single PRP, so not sure where a ctrl->page_size would come from. But now that I looked again there is a hard limit of 256 entries due to NR being a 8-bit field, so I need to cap on that at least.
