From e6a622fd6d66b83779357e3400f487fc159a7d83 Mon Sep 17 00:00:00 2001 From: Sagi Grimberg Date: Mon, 19 Nov 2018 14:11:12 -0800 Subject: [PATCH] nvmet: support fabrics sq flow control Technical proposal 8005 "fabrics SQ flow control" introduces a mode where a host and controller agree to omit sq_head pointer updates when sending nvme completions. In case the host indicated desire to operate in this mode (connect attribute) the controller will return back a connect completion with sq_head value of 0xffff as indication that it will omit sq_head pointer updates. This mode saves us an atomic update in the I/O path. Reviewed-by: Hannes Reinecke [hch: suggested better implementation] Signed-off-by: Sagi Grimberg Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- drivers/nvme/target/core.c | 23 +++++++++++++---------- drivers/nvme/target/fabrics-cmd.c | 6 ++++++ drivers/nvme/target/nvmet.h | 1 + include/linux/nvme.h | 4 ++++ 4 files changed, 24 insertions(+), 10 deletions(-) diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c index 5aa5a3cc5395..2df70010e9f2 100644 --- a/drivers/nvme/target/core.c +++ b/drivers/nvme/target/core.c @@ -597,26 +597,28 @@ struct nvmet_ns *nvmet_ns_alloc(struct nvmet_subsys *subsys, u32 nsid) return ns; } -static void __nvmet_req_complete(struct nvmet_req *req, u16 status) +static void nvmet_update_sq_head(struct nvmet_req *req) { - u32 old_sqhd, new_sqhd; - u16 sqhd; - - if (status) - nvmet_set_status(req, status); - if (req->sq->size) { + u32 old_sqhd, new_sqhd; + do { old_sqhd = req->sq->sqhd; new_sqhd = (old_sqhd + 1) % req->sq->size; } while (cmpxchg(&req->sq->sqhd, old_sqhd, new_sqhd) != old_sqhd); } - sqhd = req->sq->sqhd & 0x0000FFFF; - req->rsp->sq_head = cpu_to_le16(sqhd); + req->rsp->sq_head = cpu_to_le16(req->sq->sqhd & 0x0000FFFF); +} + +static void __nvmet_req_complete(struct nvmet_req *req, u16 status) +{ + if (!req->sq->sqhd_disabled) + nvmet_update_sq_head(req); req->rsp->sq_id = cpu_to_le16(req->sq->qid); req->rsp->command_id = req->cmd->common.command_id; - + if (status) + nvmet_set_status(req, status); if (req->ns) nvmet_put_namespace(req->ns); req->ops->queue_response(req); @@ -765,6 +767,7 @@ bool nvmet_req_init(struct nvmet_req *req, struct nvmet_cq *cq, req->sg_cnt = 0; req->transfer_len = 0; req->rsp->status = 0; + req->rsp->sq_head = 0; req->ns = NULL; /* no support for fused commands yet */ diff --git a/drivers/nvme/target/fabrics-cmd.c b/drivers/nvme/target/fabrics-cmd.c index d84ae004cb85..328ae46d8344 100644 --- a/drivers/nvme/target/fabrics-cmd.c +++ b/drivers/nvme/target/fabrics-cmd.c @@ -115,6 +115,12 @@ static u16 nvmet_install_queue(struct nvmet_ctrl *ctrl, struct nvmet_req *req) /* note: convert queue size from 0's-based value to 1's-based value */ nvmet_cq_setup(ctrl, req->cq, qid, sqsize + 1); nvmet_sq_setup(ctrl, req->sq, qid, sqsize + 1); + + if (c->cattr & NVME_CONNECT_DISABLE_SQFLOW) { + req->sq->sqhd_disabled = true; + req->rsp->sq_head = cpu_to_le16(0xffff); + } + return 0; } diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h index 03988fe9d915..547108c41ce9 100644 --- a/drivers/nvme/target/nvmet.h +++ b/drivers/nvme/target/nvmet.h @@ -106,6 +106,7 @@ struct nvmet_sq { u16 qid; u16 size; u32 sqhd; + bool sqhd_disabled; struct completion free_done; struct completion confirm_done; }; diff --git a/include/linux/nvme.h b/include/linux/nvme.h index 77d320d32ee5..e7d731776f62 100644 --- a/include/linux/nvme.h +++ b/include/linux/nvme.h @@ -1044,6 +1044,10 @@ struct nvmf_disc_rsp_page_hdr { struct nvmf_disc_rsp_page_entry entries[0]; }; +enum { + NVME_CONNECT_DISABLE_SQFLOW = (1 << 2), +}; + struct nvmf_connect_command { __u8 opcode; __u8 resv1;