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Wed, 09 Sep 2026 15:29:04 -0700 (PDT) X-Relaying-Domain: purestorage.com Received: from dev-csander.dev.purestorage.com (dev-csander.dev.purestorage.com [10.112.12.104]) by c7-smtp-2026.dev.purestorage.com (Postfix) with ESMTP id AFA1C402BE; Wed, 9 Sep 2026 16:29:03 -0600 (MDT) Received: by dev-csander.dev.purestorage.com (Postfix, from userid 1557716354) id AD682E40322; Wed, 9 Sep 2026 16:29:03 -0600 (MDT) From: Caleb Sander Mateos To: Jens Axboe , Keith Busch , Christoph Hellwig , Sagi Grimberg Cc: io-uring@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Caleb Sander Mateos Subject: [PATCH 6/6] nvme/ioctl: support fixed buffer for metadata Date: Wed, 9 Sep 2026 16:28:36 -0600 Message-ID: <20260909222836.2475352-7-csander@purestorage.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909222836.2475352-1-csander@purestorage.com> References: <20260909222836.2475352-1-csander@purestorage.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit io_uring NVMe passthrough supports using a "fixed" (registered) buffer for data, but not metadata. On high-IOPS workloads, the pinning and unpinning overhead for the metadata pages is significant and could be avoided if fixed metadata buffers were supported. Define a NVME_URING_CMD_FIXED_METADATA bit for the nvme_uring_cmd's flags field (which is currently required to be 0) to indicate that the metadata buffer belongs to a fixed buffer registered with the io_uring. The metadata fixed buffer index is specified in a metadata_buf_index field replacing the existing rsvd1 in nvme_uring_cmd. If NVME_URING_CMD_FIXED_METADATA is set, the metadata iov_iter is obtained from io_uring_cmd_import_fixed_metadata() instead of iov_iter_ubuf(). Signed-off-by: Caleb Sander Mateos --- drivers/nvme/host/ioctl.c | 21 ++++++++++++++++----- include/uapi/linux/nvme_ioctl.h | 5 ++++- 2 files changed, 20 insertions(+), 6 deletions(-) diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c index 8e722184ecf1..4da8cf92c2e0 100644 --- a/drivers/nvme/host/ioctl.c +++ b/drivers/nvme/host/ioctl.c @@ -488,21 +488,22 @@ static int nvme_uring_cmd_io(struct nvme_ctrl *ctrl, struct nvme_ns *ns, struct iov_iter iter, meta_iter; struct iov_iter *map_iter = NULL, *map_meta_iter = NULL; struct request *req; blk_opf_t rq_flags = 0; blk_mq_req_flags_t blk_flags = 0; + u8 flags = READ_ONCE(cmd->flags); u32 metadata_len, data_len; u64 metadata, addr; u32 timeout_ms; int ddir; int ret; - c.common.opcode = READ_ONCE(cmd->opcode); - c.common.flags = READ_ONCE(cmd->flags); - if (c.common.flags) + if (flags & ~NVME_URING_CMD_FIXED_METADATA) return -EINVAL; + c.common.opcode = READ_ONCE(cmd->opcode); + c.common.flags = 0; c.common.command_id = 0; c.common.nsid = cpu_to_le32(cmd->nsid); if (!nvme_validate_passthru_nsid(ctrl, ns, le32_to_cpu(c.common.nsid))) return -EINVAL; @@ -539,12 +540,22 @@ static int nvme_uring_cmd_io(struct nvme_ctrl *ctrl, struct nvme_ns *ns, return ret; map_iter = &iter; } if (data_len && metadata && metadata_len) { - iov_iter_ubuf(&meta_iter, ddir, nvme_to_user_ptr(metadata), - metadata_len); + if (flags & NVME_URING_CMD_FIXED_METADATA) { + u16 buf_index = READ_ONCE(cmd->metadata_buf_index); + + ret = io_uring_cmd_import_fixed_metadata( + ioucmd, buf_index, metadata, metadata_len, ddir, + &meta_iter, issue_flags); + if (ret < 0) + return ret; + } else { + iov_iter_ubuf(&meta_iter, ddir, nvme_to_user_ptr(metadata), + metadata_len); + } map_meta_iter = &meta_iter; } if (issue_flags & IO_URING_F_NONBLOCK) { rq_flags |= REQ_NOWAIT; diff --git a/include/uapi/linux/nvme_ioctl.h b/include/uapi/linux/nvme_ioctl.h index 2f76cba67166..93973f636b48 100644 --- a/include/uapi/linux/nvme_ioctl.h +++ b/include/uapi/linux/nvme_ioctl.h @@ -68,15 +68,18 @@ struct nvme_passthru_cmd64 { __u32 timeout_ms; __u32 rsvd2; __u64 result; }; +/* struct nvme_uring_cmd flags field bits */ +#define NVME_URING_CMD_FIXED_METADATA (1U << 0) + /* same as struct nvme_passthru_cmd64, minus the 8b result field */ struct nvme_uring_cmd { __u8 opcode; __u8 flags; - __u16 rsvd1; + __u16 metadata_buf_index; __u32 nsid; __u32 cdw2; __u32 cdw3; __u64 metadata; __u64 addr; -- 2.55.0