From: Keith Busch <kbusch@kernel.org>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: Hannes Reinecke <hare@suse.de>,
"Ewan D. Milne" <emilne@redhat.com>,
Daniel Wagner <dwagner@suse.de>,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] nvme-tcp: Check if request has started before processing it
Date: Fri, 7 May 2021 17:03:08 -0700 [thread overview]
Message-ID: <20210508000308.GB1485586@dhcp-10-100-145-180.wdc.com> (raw)
In-Reply-To: <7a45dd7f-842b-4282-909b-082b501abcdc@grimberg.me>
On Fri, May 07, 2021 at 04:22:30PM -0700, Sagi Grimberg wrote:
>
> > > > Well, that would require a modification to the CQE specification, no?
> > > > fmds was not amused when I proposed that :-(
> > >
> > > Why would that require a modification to the CQE? it's just using say
> > > 4 msbits of the command_id to a running sequence...
> >
> > I think Hannes was under the impression that the counter proposal wasn't
> > part of the "command_id". The host can encode whatever it wants in that
> > value, and the controller just has to return the same value.
>
> Yea, maybe something like this?
Yes, this looks aligned with what I was thinking. Just one minor problem
below.
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 05f31a2c64bb..96abfb0e2ddd 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -158,6 +158,7 @@ enum nvme_quirks {
> struct nvme_request {
> struct nvme_command *cmd;
> union nvme_result result;
> + u8 genctr;
> u8 retries;
> u8 flags;
> u16 status;
> @@ -497,6 +498,48 @@ struct nvme_ctrl_ops {
> int (*get_address)(struct nvme_ctrl *ctrl, char *buf, int size);
> };
>
> +/*
> + * nvme command_id is constructed as such:
> + * | xxxx | xxxxxxxxxxxx |
> + * gen request tag
> + */
> +#define nvme_cid_install_genctr(gen) ((gen & 0xf) << 12)
> +#define nvme_genctr_from_cid(cid) ((cid & 0xf000) >> 12)
> +#define nvme_tag_from_cid(cid) (cid & 0xfff)
> +
> +static inline u16 nvme_cid(struct request *rq)
> +{
> + return nvme_cid_install_genctr(nvme_req(rq)->genctr++) | rq->tag;
> +}
> +
> +static inline struct request *nvme_find_rq(struct blk_mq_tags *tags,
> + u16 command_id)
> +{
> + u8 genctr = nvme_genctr_from_cid(command_id);
> + u16 tag = nvme_tag_from_cid(command_id);
> + struct request *rq;
> +
> + rq = blk_mq_tag_to_rq(tags, tag);
> + if (unlikely(!rq)) {
> + pr_err("could not locate request for tag %#x\n",
> + tag);
> + return NULL;
> + }
> + if (unlikely(nvme_req(rq)->genctr != genctr)) {
The nvme_request 'genctr' is 8 bits, but the nvme_genctr_from_cid() can
only return 4 bits, so need to use the same mask for both.
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next prev parent reply other threads:[~2021-05-08 0:03 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-01 17:56 [PATCH v2] nvme-tcp: Check if request has started before processing it Daniel Wagner
2021-03-05 19:57 ` Sagi Grimberg
2021-03-11 9:43 ` Daniel Wagner
2021-03-15 17:16 ` Sagi Grimberg
2021-03-30 16:19 ` Ewan D. Milne
2021-03-30 17:34 ` Sagi Grimberg
2021-03-30 23:28 ` Keith Busch
2021-03-31 7:11 ` Hannes Reinecke
2021-03-31 21:01 ` Ewan D. Milne
2021-03-31 22:24 ` Sagi Grimberg
2021-04-01 6:20 ` Christoph Hellwig
2021-04-01 8:25 ` Sagi Grimberg
2021-03-31 22:37 ` Sagi Grimberg
2021-05-06 15:36 ` Hannes Reinecke
2021-05-07 20:26 ` Sagi Grimberg
2021-05-07 20:40 ` Keith Busch
2021-05-07 23:22 ` Sagi Grimberg
2021-05-08 0:03 ` Keith Busch [this message]
2021-05-09 11:30 ` Hannes Reinecke
2021-05-11 18:16 ` Sagi Grimberg
2021-05-17 14:58 ` Daniel Wagner
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