From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07425C433F5 for ; Thu, 10 Mar 2022 08:33:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240361AbiCJIeQ (ORCPT ); Thu, 10 Mar 2022 03:34:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240369AbiCJIeP (ORCPT ); Thu, 10 Mar 2022 03:34:15 -0500 Received: from mail-lf1-x132.google.com (mail-lf1-x132.google.com [IPv6:2a00:1450:4864:20::132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F1A525C864; Thu, 10 Mar 2022 00:33:12 -0800 (PST) Received: by mail-lf1-x132.google.com with SMTP id n19so8100838lfh.8; Thu, 10 Mar 2022 00:33:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=CHbpwpNAXxSBKfhDwIRmudJnsbVYGAke39m3xKYChPE=; b=L/DkDf9IC2x74KpLQAlmtKu3IaTcmokKlvdUBeJzpMWmhxTRloGr2UzxDAyiEnDr0i Pti1RmTn59LLWHUg2e4IMofp6JY+7MBZUON552Tx8W1DeqkoV9/e4P7XtL4AMxwBFtKg u/Sr4BwLmYLN/Mtw3tGxluKjrI7FqlMTwWPUYVNn+ZmXEHmchbPoNTlv4/Ff90CpXlgv ylzHH2keNi9xhF1r7Q0MRn3Ub+yq1KAXSCncY8uEUnoU6Fu9sNGPQ37dxGyWlJwiSfu1 UL/rAL+3AC+lv3hDPYiyUBmk+qTPa//Fj4oybspPvTDRe4DHwlFEhYw0KguCpqtJyQG+ zeyw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=CHbpwpNAXxSBKfhDwIRmudJnsbVYGAke39m3xKYChPE=; b=dzZeH0virluXIepJsCkoFStkbNj+CLSb5UHJKgGHJFgoroZBlWQGuYGOB8wEHKPYjE 0i8wAGwJqvilhTO38LNAZ2RHtriTQKXUAnp9+jbihevWeDN3vPdqUpfPylQEXfODjukd Nbj9KHlIgIAqTnhHokQ4NeoF1bChzoYmgWQ+WNTaEha08cwldo2F7Li2DiaL3ln9Sx/5 PDQI3C0NxwgaNbPYI+tbreKdwO+F4W9jHdZph7TmecbqlPe+qKqQtIwM8QAgpAjRMxIj feCrIVNescAAsMxUk6eFY8xDdtqZpFTIKrzzSrKnuDVap+Tfu8UuFnIGBMGEempHc8ah O1cg== X-Gm-Message-State: AOAM533vsm+8ety/yrbTgXa0r+4JKlejaGvcS1lV3xLTZwkEhkH/Ljlo M82uLibHilZLxOJPNKN+PCV8ex0x5I/m1P44Ifw= X-Google-Smtp-Source: ABdhPJywu0uHNvT9G5e/CDKAa05XQh1Gy4awrCqbwE+r3qeyU8kGngSEue7+mGmQJRsKiqPISGtXBRz7RiuLKgg+8eg= X-Received: by 2002:ac2:5e2f:0:b0:443:671b:cead with SMTP id o15-20020ac25e2f000000b00443671bceadmr2249180lfg.306.1646901190862; Thu, 10 Mar 2022 00:33:10 -0800 (PST) MIME-Version: 1.0 References: <20220308152105.309618-1-joshi.k@samsung.com> <20220308152105.309618-6-joshi.k@samsung.com> <7e163c463c4d420abf68ae2a2a061cc8@kioxia.com> In-Reply-To: <7e163c463c4d420abf68ae2a2a061cc8@kioxia.com> From: Kanchan Joshi Date: Thu, 10 Mar 2022 14:02:46 +0530 Message-ID: Subject: Re: [PATCH 05/17] nvme: wire-up support for async-passthru on char-device. To: Clay Mayers Cc: Kanchan Joshi , "axboe@kernel.dk" , "hch@lst.de" , "kbusch@kernel.org" , "asml.silence@gmail.com" , "io-uring@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-block@vger.kernel.org" , "sbates@raithlin.com" , "logang@deltatee.com" , "pankydev8@gmail.com" , "javier@javigon.com" , "mcgrof@kernel.org" , "a.manzanares@samsung.com" , "anuj20.g@samsung.com" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Thu, Mar 10, 2022 at 5:32 AM Clay Mayers wrote: > > > From: Linux-nvme On Behalf Of > > Kanchan Joshi > > Sent: Tuesday, March 8, 2022 7:21 AM > > To: axboe@kernel.dk; hch@lst.de; kbusch@kernel.org; > > asml.silence@gmail.com > > Cc: io-uring@vger.kernel.org; linux-nvme@lists.infradead.org; linux- > > block@vger.kernel.org; sbates@raithlin.com; logang@deltatee.com; > > pankydev8@gmail.com; javier@javigon.com; mcgrof@kernel.org; > > a.manzanares@samsung.com; joshiiitr@gmail.com; anuj20.g@samsung.com > > Subject: [PATCH 05/17] nvme: wire-up support for async-passthru on char- > > device. > > > > Introduce handler for fops->async_cmd(), implementing async passthru > > on char device (/dev/ngX). The handler supports NVME_IOCTL_IO64_CMD > > for > > read and write commands. Returns failure for other commands. > > This is low overhead path for processing the inline commands housed > > inside io_uring's sqe. Neither the commmand is fetched via > > copy_from_user, nor the result (inside passthru command) is updated via > > put_user. > > > > Signed-off-by: Kanchan Joshi > > Signed-off-by: Anuj Gupta > > --- > > drivers/nvme/host/core.c | 1 + > > drivers/nvme/host/ioctl.c | 205 ++++++++++++++++++++++++++++------ > > drivers/nvme/host/multipath.c | 1 + > > drivers/nvme/host/nvme.h | 3 + > > 4 files changed, 178 insertions(+), 32 deletions(-) > > > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > > index 159944499c4f..3fe8f5901cd9 100644 > > --- a/drivers/nvme/host/core.c > > +++ b/drivers/nvme/host/core.c > > @@ -3667,6 +3667,7 @@ static const struct file_operations > > nvme_ns_chr_fops = { > > .release = nvme_ns_chr_release, > > .unlocked_ioctl = nvme_ns_chr_ioctl, > > .compat_ioctl = compat_ptr_ioctl, > > + .async_cmd = nvme_ns_chr_async_cmd, > > }; > > > > static int nvme_add_ns_cdev(struct nvme_ns *ns) > > diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c > > index 5c9cd9695519..1df270b47af5 100644 > > --- a/drivers/nvme/host/ioctl.c > > +++ b/drivers/nvme/host/ioctl.c > > @@ -18,6 +18,76 @@ static void __user *nvme_to_user_ptr(uintptr_t ptrval) > > ptrval = (compat_uptr_t)ptrval; > > return (void __user *)ptrval; > > } > > +/* > > + * This overlays struct io_uring_cmd pdu. > > + * Expect build errors if this grows larger than that. > > + */ > > +struct nvme_uring_cmd_pdu { > > + u32 meta_len; > > + union { > > + struct bio *bio; > > + struct request *req; > > + }; > > + void *meta; /* kernel-resident buffer */ > > + void __user *meta_buffer; > > +} __packed; > > + > > +static struct nvme_uring_cmd_pdu *nvme_uring_cmd_pdu(struct > > io_uring_cmd *ioucmd) > > +{ > > + return (struct nvme_uring_cmd_pdu *)&ioucmd->pdu; > > +} > > + > > +static void nvme_pt_task_cb(struct io_uring_cmd *ioucmd) > > +{ > > + struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd); > > + struct request *req = pdu->req; > > + int status; > > + struct bio *bio = req->bio; > > + > > + if (nvme_req(req)->flags & NVME_REQ_CANCELLED) > > + status = -EINTR; > > + else > > + status = nvme_req(req)->status; > > + > > + /* we can free request */ > > + blk_mq_free_request(req); > > + blk_rq_unmap_user(bio); > > + > > + if (!status && pdu->meta_buffer) { > > + if (copy_to_user(pdu->meta_buffer, pdu->meta, pdu- > > >meta_len)) > > + status = -EFAULT; > > + } > > + kfree(pdu->meta); > > + > > + io_uring_cmd_done(ioucmd, status); > > +} > > + > > +static void nvme_end_async_pt(struct request *req, blk_status_t err) > > +{ > > + struct io_uring_cmd *ioucmd = req->end_io_data; > > + struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd); > > + /* extract bio before reusing the same field for request */ > > + struct bio *bio = pdu->bio; > > + > > + pdu->req = req; > > + req->bio = bio; > > + /* this takes care of setting up task-work */ > > + io_uring_cmd_complete_in_task(ioucmd, nvme_pt_task_cb); > > +} > > + > > +static void nvme_setup_uring_cmd_data(struct request *rq, > > + struct io_uring_cmd *ioucmd, void *meta, > > + void __user *meta_buffer, u32 meta_len) > > +{ > > + struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd); > > + > > + /* to free bio on completion, as req->bio will be null at that time */ > > + pdu->bio = rq->bio; > > + pdu->meta = meta; > > + pdu->meta_buffer = meta_buffer; > > + pdu->meta_len = meta_len; > > + rq->end_io_data = ioucmd; > > +} > > > > static void *nvme_add_user_metadata(struct bio *bio, void __user *ubuf, > > unsigned len, u32 seed, bool write) > > @@ -56,7 +126,8 @@ static void *nvme_add_user_metadata(struct bio > > *bio, void __user *ubuf, > > static int nvme_submit_user_cmd(struct request_queue *q, > > struct nvme_command *cmd, void __user *ubuffer, > > unsigned bufflen, void __user *meta_buffer, unsigned > > meta_len, > > - u32 meta_seed, u64 *result, unsigned timeout) > > + u32 meta_seed, u64 *result, unsigned timeout, > > + struct io_uring_cmd *ioucmd) > > { > > bool write = nvme_is_write(cmd); > > struct nvme_ns *ns = q->queuedata; > > @@ -64,9 +135,15 @@ static int nvme_submit_user_cmd(struct > > request_queue *q, > > struct request *req; > > struct bio *bio = NULL; > > void *meta = NULL; > > + unsigned int rq_flags = 0; > > + blk_mq_req_flags_t blk_flags = 0; > > int ret; > > > > - req = nvme_alloc_request(q, cmd, 0, 0); > > + if (ioucmd && (ioucmd->flags & IO_URING_F_NONBLOCK)) { > > + rq_flags |= REQ_NOWAIT; > > + blk_flags |= BLK_MQ_REQ_NOWAIT; > > + } > > + req = nvme_alloc_request(q, cmd, blk_flags, rq_flags); > > if (IS_ERR(req)) > > return PTR_ERR(req); > > > > @@ -92,6 +169,19 @@ static int nvme_submit_user_cmd(struct > > request_queue *q, > > req->cmd_flags |= REQ_INTEGRITY; > > } > > } > > + if (ioucmd) { /* async dispatch */ > > + if (cmd->common.opcode == nvme_cmd_write || > > + cmd->common.opcode == nvme_cmd_read) { > > + nvme_setup_uring_cmd_data(req, ioucmd, meta, > > meta_buffer, > > + meta_len); > > + blk_execute_rq_nowait(req, 0, nvme_end_async_pt); > > + return 0; > > + } else { > > + /* support only read and write for now. */ > > + ret = -EINVAL; > > + goto out_meta; > > + } > > + } > > > > ret = nvme_execute_passthru_rq(req); > > if (result) > > @@ -100,6 +190,7 @@ static int nvme_submit_user_cmd(struct > > request_queue *q, > > if (copy_to_user(meta_buffer, meta, meta_len)) > > ret = -EFAULT; > > } > > + out_meta: > > kfree(meta); > > out_unmap: > > if (bio) > > @@ -170,7 +261,8 @@ static int nvme_submit_io(struct nvme_ns *ns, struct > > nvme_user_io __user *uio) > > > > return nvme_submit_user_cmd(ns->queue, &c, > > nvme_to_user_ptr(io.addr), length, > > - metadata, meta_len, lower_32_bits(io.slba), NULL, > > 0); > > + metadata, meta_len, lower_32_bits(io.slba), NULL, 0, > > + NULL); > > } > > > > static bool nvme_validate_passthru_nsid(struct nvme_ctrl *ctrl, > > @@ -224,7 +316,7 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, > > struct nvme_ns *ns, > > status = nvme_submit_user_cmd(ns ? ns->queue : ctrl->admin_q, &c, > > nvme_to_user_ptr(cmd.addr), cmd.data_len, > > nvme_to_user_ptr(cmd.metadata), > > cmd.metadata_len, > > - 0, &result, timeout); > > + 0, &result, timeout, NULL); > > > > if (status >= 0) { > > if (put_user(result, &ucmd->result)) > > @@ -235,45 +327,53 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, > > struct nvme_ns *ns, > > } > > > > static int nvme_user_cmd64(struct nvme_ctrl *ctrl, struct nvme_ns *ns, > > - struct nvme_passthru_cmd64 __user *ucmd) > > + struct nvme_passthru_cmd64 __user *ucmd, > > + struct io_uring_cmd *ioucmd) > > { > > - struct nvme_passthru_cmd64 cmd; > > + struct nvme_passthru_cmd64 cmd, *cptr; > > struct nvme_command c; > > unsigned timeout = 0; > > int status; > > > > if (!capable(CAP_SYS_ADMIN)) > > return -EACCES; > > - if (copy_from_user(&cmd, ucmd, sizeof(cmd))) > > - return -EFAULT; > > - if (cmd.flags) > > + if (!ioucmd) { > > + if (copy_from_user(&cmd, ucmd, sizeof(cmd))) > > + return -EFAULT; > > + cptr = &cmd; > > + } else { > > + if (ioucmd->cmd_len != sizeof(struct nvme_passthru_cmd64)) > > + return -EINVAL; > > + cptr = (struct nvme_passthru_cmd64 *)ioucmd->cmd; > > + } > > + if (cptr->flags) > > return -EINVAL; > > - if (!nvme_validate_passthru_nsid(ctrl, ns, cmd.nsid)) > > + if (!nvme_validate_passthru_nsid(ctrl, ns, cptr->nsid)) > > return -EINVAL; > > > > memset(&c, 0, sizeof(c)); > > - c.common.opcode = cmd.opcode; > > - c.common.flags = cmd.flags; > > - c.common.nsid = cpu_to_le32(cmd.nsid); > > - c.common.cdw2[0] = cpu_to_le32(cmd.cdw2); > > - c.common.cdw2[1] = cpu_to_le32(cmd.cdw3); > > - c.common.cdw10 = cpu_to_le32(cmd.cdw10); > > - c.common.cdw11 = cpu_to_le32(cmd.cdw11); > > - c.common.cdw12 = cpu_to_le32(cmd.cdw12); > > - c.common.cdw13 = cpu_to_le32(cmd.cdw13); > > - c.common.cdw14 = cpu_to_le32(cmd.cdw14); > > - c.common.cdw15 = cpu_to_le32(cmd.cdw15); > > - > > - if (cmd.timeout_ms) > > - timeout = msecs_to_jiffies(cmd.timeout_ms); > > + c.common.opcode = cptr->opcode; > > + c.common.flags = cptr->flags; > > + c.common.nsid = cpu_to_le32(cptr->nsid); > > + c.common.cdw2[0] = cpu_to_le32(cptr->cdw2); > > + c.common.cdw2[1] = cpu_to_le32(cptr->cdw3); > > + c.common.cdw10 = cpu_to_le32(cptr->cdw10); > > + c.common.cdw11 = cpu_to_le32(cptr->cdw11); > > + c.common.cdw12 = cpu_to_le32(cptr->cdw12); > > + c.common.cdw13 = cpu_to_le32(cptr->cdw13); > > + c.common.cdw14 = cpu_to_le32(cptr->cdw14); > > + c.common.cdw15 = cpu_to_le32(cptr->cdw15); > > + > > + if (cptr->timeout_ms) > > + timeout = msecs_to_jiffies(cptr->timeout_ms); > > > > status = nvme_submit_user_cmd(ns ? ns->queue : ctrl->admin_q, &c, > > - nvme_to_user_ptr(cmd.addr), cmd.data_len, > > - nvme_to_user_ptr(cmd.metadata), > > cmd.metadata_len, > > - 0, &cmd.result, timeout); > > + nvme_to_user_ptr(cptr->addr), cptr->data_len, > > + nvme_to_user_ptr(cptr->metadata), cptr- > > >metadata_len, > > + 0, &cptr->result, timeout, ioucmd); > > > > - if (status >= 0) { > > - if (put_user(cmd.result, &ucmd->result)) > > + if (!ioucmd && status >= 0) { > > + if (put_user(cptr->result, &ucmd->result)) > > return -EFAULT; > > } > > > > @@ -296,7 +396,7 @@ static int nvme_ctrl_ioctl(struct nvme_ctrl *ctrl, > > unsigned int cmd, > > case NVME_IOCTL_ADMIN_CMD: > > return nvme_user_cmd(ctrl, NULL, argp); > > case NVME_IOCTL_ADMIN64_CMD: > > - return nvme_user_cmd64(ctrl, NULL, argp); > > + return nvme_user_cmd64(ctrl, NULL, argp, NULL); > > default: > > return sed_ioctl(ctrl->opal_dev, cmd, argp); > > } > > @@ -340,7 +440,7 @@ static int nvme_ns_ioctl(struct nvme_ns *ns, > > unsigned int cmd, > > case NVME_IOCTL_SUBMIT_IO: > > return nvme_submit_io(ns, argp); > > case NVME_IOCTL_IO64_CMD: > > - return nvme_user_cmd64(ns->ctrl, ns, argp); > > + return nvme_user_cmd64(ns->ctrl, ns, argp, NULL); > > default: > > return -ENOTTY; > > } > > @@ -369,6 +469,33 @@ long nvme_ns_chr_ioctl(struct file *file, unsigned int > > cmd, unsigned long arg) > > return __nvme_ioctl(ns, cmd, (void __user *)arg); > > } > > > > +static int nvme_ns_async_ioctl(struct nvme_ns *ns, struct io_uring_cmd > > *ioucmd) > > +{ > > + int ret; > > + > > + BUILD_BUG_ON(sizeof(struct nvme_uring_cmd_pdu) > > > sizeof(ioucmd->pdu)); > > + > > + switch (ioucmd->cmd_op) { > > + case NVME_IOCTL_IO64_CMD: > > + ret = nvme_user_cmd64(ns->ctrl, ns, NULL, ioucmd); > > + break; > > + default: > > + ret = -ENOTTY; > > + } > > + > > + if (ret >= 0) > > + ret = -EIOCBQUEUED; > > + return ret; > > +} > > ret can equal -EAGAIN, which will cause io_uring to reissue the cmd > from a worker thread. This can happen when ioucmd->flags has > IO_URING_F_NONBLOCK set causing nvme_alloc_request() to return > -EAGAIN when there are no tags available. > > Either -EAGAIN needs to be remapped or force set REQ_F_NOWAIT in the > io_uring cmd request in patch 3 (the 2nd option is untested). This patch already sets REQ_F_NOWAIT for IO_URING_F_NONBLOCK flag. Here: + if (ioucmd && (ioucmd->flags & IO_URING_F_NONBLOCK)) { + rq_flags |= REQ_NOWAIT; + blk_flags |= BLK_MQ_REQ_NOWAIT; + } + req = nvme_alloc_request(q, cmd, blk_flags, rq_flags); And if -EAGAIN goes to io_uring, we don't try to setup the worker and instead return the error to userspace for retry. Here is the relevant fragment from Patch 3: + ioucmd->flags |= issue_flags; + ret = file->f_op->async_cmd(ioucmd); + /* queued async, consumer will call io_uring_cmd_done() when complete */ + if (ret == -EIOCBQUEUED) + return 0; + io_uring_cmd_done(ioucmd, ret); > > + > > +int nvme_ns_chr_async_cmd(struct io_uring_cmd *ioucmd) > > +{ > > + struct nvme_ns *ns = container_of(file_inode(ioucmd->file)->i_cdev, > > + struct nvme_ns, cdev); > > + > > + return nvme_ns_async_ioctl(ns, ioucmd); > > +} > > + > > #ifdef CONFIG_NVME_MULTIPATH > > static int nvme_ns_head_ctrl_ioctl(struct nvme_ns *ns, unsigned int cmd, > > void __user *argp, struct nvme_ns_head *head, int srcu_idx) > > @@ -412,6 +539,20 @@ int nvme_ns_head_ioctl(struct block_device *bdev, > > fmode_t mode, > > return ret; > > } > > > > +int nvme_ns_head_chr_async_cmd(struct io_uring_cmd *ioucmd) > > +{ > > + struct cdev *cdev = file_inode(ioucmd->file)->i_cdev; > > + struct nvme_ns_head *head = container_of(cdev, struct > > nvme_ns_head, cdev); > > + int srcu_idx = srcu_read_lock(&head->srcu); > > + struct nvme_ns *ns = nvme_find_path(head); > > + int ret = -EWOULDBLOCK; > > -EWOULDBLOCK has the same value as -EAGAIN so the same issue > Is here as with nvme_ns_async_ioctl() returning it. Same as above. > > + > > + if (ns) > > + ret = nvme_ns_async_ioctl(ns, ioucmd); > > + srcu_read_unlock(&head->srcu, srcu_idx); > > + return ret; > > +} > > + > > long nvme_ns_head_chr_ioctl(struct file *file, unsigned int cmd, > > unsigned long arg) > > { > > @@ -480,7 +621,7 @@ long nvme_dev_ioctl(struct file *file, unsigned int > > cmd, > > case NVME_IOCTL_ADMIN_CMD: > > return nvme_user_cmd(ctrl, NULL, argp); > > case NVME_IOCTL_ADMIN64_CMD: > > - return nvme_user_cmd64(ctrl, NULL, argp); > > + return nvme_user_cmd64(ctrl, NULL, argp, NULL); > > case NVME_IOCTL_IO_CMD: > > return nvme_dev_user_cmd(ctrl, argp); > > case NVME_IOCTL_RESET: > > diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c > > index f8bf6606eb2f..1d798d09456f 100644 > > --- a/drivers/nvme/host/multipath.c > > +++ b/drivers/nvme/host/multipath.c > > @@ -459,6 +459,7 @@ static const struct file_operations > > nvme_ns_head_chr_fops = { > > .release = nvme_ns_head_chr_release, > > .unlocked_ioctl = nvme_ns_head_chr_ioctl, > > .compat_ioctl = compat_ptr_ioctl, > > + .async_cmd = nvme_ns_head_chr_async_cmd, > > }; > > > > static int nvme_add_ns_head_cdev(struct nvme_ns_head *head) > > diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h > > index b32f4e2c68fd..e6a30543d7c8 100644 > > --- a/drivers/nvme/host/nvme.h > > +++ b/drivers/nvme/host/nvme.h > > @@ -16,6 +16,7 @@ > > #include > > #include > > #include > > +#include > > > > #include > > > > @@ -752,6 +753,8 @@ long nvme_ns_head_chr_ioctl(struct file *file, > > unsigned int cmd, > > unsigned long arg); > > long nvme_dev_ioctl(struct file *file, unsigned int cmd, > > unsigned long arg); > > +int nvme_ns_chr_async_cmd(struct io_uring_cmd *ioucmd); > > +int nvme_ns_head_chr_async_cmd(struct io_uring_cmd *ioucmd); > > int nvme_getgeo(struct block_device *bdev, struct hd_geometry *geo); > > > > extern const struct attribute_group *nvme_ns_id_attr_groups[]; > > -- > > 2.25.1 > > On 5.10 with our version of this patch, I've seen that returning -EAGAIN to > io_uring results in poisoned bios and crashed kernel threads (NULL current->mm) > while constructing the async pass through request. I looked at > git://git.kernel.dk/linux-block and git://git.infradead.org/nvme.git > and as best as I can tell, the same thing will happen. As pointed above in the snippet, any error except -EIOCBQUEUED is just posted in CQE during submission itself. So I do not see why -EAGAIN should cause trouble, at least in this patchset. FWIW- I tested by forcefully returning -EAGAIN from nvme, and also tag saturation case (which also returns -EAGAIN) and did not see that sort of issue. Please take this series for a spin. Kernel: for-next in linux-block, on top of commit 9e9d83faa ("io_uring: Remove unneeded test in io_run_task_work_sig")