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From:   Niklas Cassel <nks@flawful.org>
To:     Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
        Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Cc:     Niklas Cassel <niklas.cassel@wdc.com>,
        linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH] nvme-pci: don't simple map sgl when sgls are disabled
Date:   Fri,  9 Apr 2021 20:12:55 +0200
Message-Id: <20210409181255.101847-1-nks@flawful.org>
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From: Niklas Cassel <niklas.cassel@wdc.com>

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>
---
 drivers/nvme/host/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index d47bb18b976a..b06e685d1250 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -854,7 +854,7 @@ 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);
-- 
2.30.2