[PATCH] nvme-pci: Set the prp2 correctly when using more than 4k page

[PATCH] nvme-pci: Set the prp2 correctly when using more than 4k page

[Kevin Hao]

In the current code, the nvme is using a fixed 4k PRP entry size,
but if the kernel use a page size which is more than 4k, we should
consider the situation that the bv_offset may be larger than the
dev->ctrl.page_size. Otherwise we may miss setting the prp2 and then
cause the command can't be executed correctly.

Fixes: dff824b2aadb ("nvme-pci: optimize mapping of small single segment requests")
Cc: stable@vger.kernel.org
Signed-off-by: Kevin Hao <haokexin@gmail.com>
---
 drivers/nvme/host/pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index bb88681f4dc3..fa647608c907 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -773,7 +773,8 @@ static blk_status_t nvme_setup_prp_simple(struct nvme_dev *dev,
 		struct bio_vec *bv)
 {
 	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
-	unsigned int first_prp_len = dev->ctrl.page_size - bv->bv_offset;
+	unsigned int offset = bv->bv_offset % dev->ctrl.page_size;
+	unsigned int first_prp_len = dev->ctrl.page_size - offset;
 
 	iod->first_dma = dma_map_bvec(dev->dev, bv, rq_dma_dir(req), 0);
 	if (dma_mapping_error(dev->dev, iod->first_dma))
-- 
2.14.4


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Re: [PATCH] nvme-pci: Set the prp2 correctly when using more than 4k page

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

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Re: [PATCH] nvme-pci: Set the prp2 correctly when using more than 4k page

[Keith Busch]

On 10/17/19, 1:40 AM, "Kevin Hao" <haokexin@gmail.com> wrote:
> +	unsigned int offset = bv->bv_offset % dev->ctrl.page_size;

Can we do this without the modulo in the io path? The page_size is a power of
2, so this should work:

	unsigned int offset = bv->bv_offset & (dev->ctrl.page_size - 1);

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Re: [PATCH] nvme-pci: Set the prp2 correctly when using more than 4k page

[Kevin Hao]

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On Thu, Oct 17, 2019 at 11:38:07AM -0600, Keith Busch wrote:
> On 10/17/19, 1:40 AM, "Kevin Hao" <haokexin@gmail.com> wrote:
> > +	unsigned int offset = bv->bv_offset % dev->ctrl.page_size;
> 
> Can we do this without the modulo in the io path? The page_size is a power of
> 2, so this should work:
> 
> 	unsigned int offset = bv->bv_offset & (dev->ctrl.page_size - 1);

Sure. V2 is coming soon.

Thanks,
Kevin


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[PATCH v2] nvme-pci: Set the prp2 correctly when using more than 4k page

[Kevin Hao]

In the current code, the nvme is using a fixed 4k PRP entry size,
but if the kernel use a page size which is more than 4k, we should
consider the situation that the bv_offset may be larger than the
dev->ctrl.page_size. Otherwise we may miss setting the prp2 and then
cause the command can't be executed correctly.

Fixes: dff824b2aadb ("nvme-pci: optimize mapping of small single segment requests")
Cc: stable@vger.kernel.org
Signed-off-by: Kevin Hao <haokexin@gmail.com>
---
v2: Avoid using modulo as suggested by Keith Busch.

 drivers/nvme/host/pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index bb88681f4dc3..c7ba2b16a93b 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -773,7 +773,8 @@ static blk_status_t nvme_setup_prp_simple(struct nvme_dev *dev,
 		struct bio_vec *bv)
 {
 	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
-	unsigned int first_prp_len = dev->ctrl.page_size - bv->bv_offset;
+	unsigned int offset = bv->bv_offset & (dev->ctrl.page_size - 1);
+	unsigned int first_prp_len = dev->ctrl.page_size - offset;
 
 	iod->first_dma = dma_map_bvec(dev->dev, bv, rq_dma_dir(req), 0);
 	if (dma_mapping_error(dev->dev, iod->first_dma))
-- 
2.14.4


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Re: [PATCH v2] nvme-pci: Set the prp2 correctly when using more than 4k page

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

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Re: [PATCH v2] nvme-pci: Set the prp2 correctly when using more than 4k page

[Keith Busch]

Applied to nvme-5.4, thanks.

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