nvme: allow for size limitations from transport drivers

Some transport drivers may have a lower transfer size than
the controller. So allow the transport to set it in the
controller max_hw_sectors.

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/nvme/host/core.c

@@ -1105,6 +1105,7 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 	struct nvme_id_ctrl *id;
 	u64 cap;
 	int ret, page_shift;
+	u32 max_hw_sectors;
 
 	ret = ctrl->ops->reg_read32(ctrl, NVME_REG_VS, &ctrl->vs);
 	if (ret) {
@@ -1137,9 +1138,11 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 	memcpy(ctrl->model, id->mn, sizeof(id->mn));
 	memcpy(ctrl->firmware_rev, id->fr, sizeof(id->fr));
 	if (id->mdts)
-		ctrl->max_hw_sectors = 1 << (id->mdts + page_shift - 9);
+		max_hw_sectors = 1 << (id->mdts + page_shift - 9);
 	else
-		ctrl->max_hw_sectors = UINT_MAX;
+		max_hw_sectors = UINT_MAX;
+	ctrl->max_hw_sectors =
+		min_not_zero(ctrl->max_hw_sectors, max_hw_sectors);
 
 	if ((ctrl->quirks & NVME_QUIRK_STRIPE_SIZE) && id->vs[3]) {
 		unsigned int max_hw_sectors;