* [PATCH] nvme-pci: calculate iod and avg_seg_size just before use them
@ 2018-01-11 5:09 Jianchao Wang
2018-01-11 15:48 ` Keith Busch
0 siblings, 1 reply; 4+ messages in thread
From: Jianchao Wang @ 2018-01-11 5:09 UTC (permalink / raw)
To: keith.busch, axboe, hch, sagi; +Cc: linux-nvme, linux-kernel
The calculation of iod and avg_seg_size maybe meaningless if
nvme_pci_use_sgls returns before uses them. So calculate
just before use them.
Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
---
drivers/nvme/host/pci.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 0530432..733b4f4 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -772,16 +772,19 @@ static blk_status_t nvme_pci_setup_sgls(struct nvme_dev *dev,
static inline bool nvme_pci_use_sgls(struct nvme_dev *dev, struct request *req)
{
- struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
+ struct nvme_iod *iod;
unsigned int avg_seg_size;
- avg_seg_size = DIV_ROUND_UP(blk_rq_payload_bytes(req),
- blk_rq_nr_phys_segments(req));
-
if (!(dev->ctrl.sgls & ((1 << 0) | (1 << 1))))
return false;
+
+ iod = blk_mq_rq_to_pdu(req);
if (!iod->nvmeq->qid)
return false;
+
+ avg_seg_size = DIV_ROUND_UP(blk_rq_payload_bytes(req),
+ blk_rq_nr_phys_segments(req));
+
if (!sgl_threshold || avg_seg_size < sgl_threshold)
return false;
return true;
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] nvme-pci: calculate iod and avg_seg_size just before use them
2018-01-11 5:09 [PATCH] nvme-pci: calculate iod and avg_seg_size just before use them Jianchao Wang
@ 2018-01-11 15:48 ` Keith Busch
2018-01-12 1:31 ` jianchao.wang
2018-01-14 9:28 ` Sagi Grimberg
0 siblings, 2 replies; 4+ messages in thread
From: Keith Busch @ 2018-01-11 15:48 UTC (permalink / raw)
To: Jianchao Wang; +Cc: axboe, hch, sagi, linux-nvme, linux-kernel
On Thu, Jan 11, 2018 at 01:09:39PM +0800, Jianchao Wang wrote:
> The calculation of iod and avg_seg_size maybe meaningless if
> nvme_pci_use_sgls returns before uses them. So calculate
> just before use them.
The compiler will do the right thing here, but I see what you mean. I
think Christoph has some SGL improvements coming, though, that will
obviate this.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] nvme-pci: calculate iod and avg_seg_size just before use them
2018-01-11 15:48 ` Keith Busch
@ 2018-01-12 1:31 ` jianchao.wang
2018-01-14 9:28 ` Sagi Grimberg
1 sibling, 0 replies; 4+ messages in thread
From: jianchao.wang @ 2018-01-12 1:31 UTC (permalink / raw)
To: Keith Busch; +Cc: axboe, hch, sagi, linux-nvme, linux-kernel
Hi Keith
Thanks for your kindly response.
On 01/11/2018 11:48 PM, Keith Busch wrote:
> On Thu, Jan 11, 2018 at 01:09:39PM +0800, Jianchao Wang wrote:
>> The calculation of iod and avg_seg_size maybe meaningless if
>> nvme_pci_use_sgls returns before uses them. So calculate
>> just before use them.
>
> The compiler will do the right thing here, but I see what you mean. I
> think Christoph has some SGL improvements coming, though, that will
> obviate this.
>
Yeah, that's great.
Thanks
Jianchao
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] nvme-pci: calculate iod and avg_seg_size just before use them
2018-01-11 15:48 ` Keith Busch
2018-01-12 1:31 ` jianchao.wang
@ 2018-01-14 9:28 ` Sagi Grimberg
1 sibling, 0 replies; 4+ messages in thread
From: Sagi Grimberg @ 2018-01-14 9:28 UTC (permalink / raw)
To: Keith Busch, Jianchao Wang; +Cc: axboe, hch, linux-nvme, linux-kernel
>> The calculation of iod and avg_seg_size maybe meaningless if
>> nvme_pci_use_sgls returns before uses them. So calculate
>> just before use them.
>
> The compiler will do the right thing here, but I see what you mean. I
> think Christoph has some SGL improvements coming, though, that will
> obviate this.
I think that if its not coming for 4.16, it should be easy enough to
take it in.
FWIW,
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2018-01-11 5:09 [PATCH] nvme-pci: calculate iod and avg_seg_size just before use them Jianchao Wang
2018-01-11 15:48 ` Keith Busch
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2018-01-14 9:28 ` Sagi Grimberg
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