nvme-pci: don't simple map sgl when sgls are disabled

[ Upstream commit e51183be1fa96dc6d3cd11b3c25a0f595807315e ]

According to the module parameter description for sgl_threshold,
a value of 0 means that SGLs are disabled.

If SGLs are disabled, we should respect that, even for the case
where the request is made up of a single physical segment.

Fixes: 297910571f08 ("nvme-pci: optimize mapping single segment requests using SGLs")
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 716039e..c1f3446 100644 (file)
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -852,7 +852,7 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
                                return nvme_setup_prp_simple(dev, req,
                                                             &cmnd->rw, &bv);
 
-                       if (iod->nvmeq->qid &&
+                       if (iod->nvmeq->qid && sgl_threshold &&
                            dev->ctrl.sgls & ((1 << 0) | (1 << 1)))
                                return nvme_setup_sgl_simple(dev, req,
                                                             &cmnd->rw, &bv);