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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E7600C25B7A for ; Wed, 22 May 2024 21:36:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=EYRD4+gZk4WizP4p9em+YVZ4sWQq44kUyRcamWC81LM=; b=Z6D2cILU61PhwspAWeaBm3r2BY sRvTVQIAWOBSIOXPjJcWaaVdluV2g44RJnlQ1YME6IoIWlT06Hx3geBhT6Gb8EumjC7NKvOslRzZS LFWftE6bfKu1VZ84E4wtzQJwhEz5gnto3IK9owEK94JM9EKAz8VX03gHgv6E6ugsiGzs1pR9OQZ7l KHGn+SV4cdQhHxEbrjnHrgOL+NuordH6hCdFQmdgstODtS7wrK8Tt7ojkIGjNTliXkZQzlVeDRcL3 08NC2Kv2H++lnMtYUaR+QZMjfoiQR16jHsNt+D8paEDdfXTiiXuc9r0l/UDnNW0FhEFKqIYPnq0Q8 b3VJzmXA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9tdN-00000004ATe-2vTG; Wed, 22 May 2024 21:36:29 +0000 Received: from sin.source.kernel.org ([145.40.73.55]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9tdK-00000004ASu-4Bsc for linux-nvme@lists.infradead.org; Wed, 22 May 2024 21:36:28 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id BB30DCE0B57; Wed, 22 May 2024 21:36:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A7DBDC2BBFC; Wed, 22 May 2024 21:36:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1716413782; bh=N1FwWzcOSWZaO+shg26gJg6z1yhNQ0C9raiU4/p/750=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cEj3q1JRH6IO1TOmYXNH7ODd1EuD3J/jqXElKhK2GLJKXavMzzf4qCRnmCDDn1wUm Rvy6uhn6Yjt2VncG278fQSbXGKEG4iNAN/BE/jSoPmmx7deuYvhbPnlOvyPWKi13bT w6v88rX8VwpOXnpdkljnQJbpRpcuqKyX2FKsDw23cSMoV4aFAEcpPCXRwGY06db1fX hnuQLdxLBRI03o8tpTr7WJdaENN+wRgskP9/k/MuuHna/oY/UDMKsQz789glcoUf8i 2CmdxMGSyOaY4yAuBulHz7ylC3K19Kjwdb276Dp+0naC9aBRAKllm0ZLxzhPhBX4Kx 0uLzjfhNrYrsw== Date: Wed, 22 May 2024 15:36:19 -0600 From: Keith Busch To: Sagi Grimberg Cc: Christoph Hellwig , Shinichiro Kawasaki , "linux-nvme@lists.infradead.org" Subject: Re: [PATCH] nvme-pci: silence a lockdep complaint Message-ID: References: <20240522091534.472449-1-sagi@grimberg.me> <20240522162845.GA16783@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240522_143627_478525_D6793336 X-CRM114-Status: GOOD ( 31.90 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Wed, May 22, 2024 at 09:00:34PM +0300, Sagi Grimberg wrote: > I don't understand lockdep well enough to do that. This warning > exists for 6 months now. The conclusion that Keith came to (and I agreed) > is that it can't happen, because nvme_timeout handler will not disable the > device while the ctrl reset_work is running, the ctrl state machine will > prevent that from happening. > > There was an attempt to convert namespaces_rwsem a srcu, but my comment to > that was that this is an intrusive change for a complaint that we think is a > false-positive. I'll play devil's advocate and suggest there might be some whacky timeout_work, scan_work, reset_work, and pciehp irq that could result in a read, write, wait, read deadlock. I don't think it can happen, but it's harder to prove that. The below patch is what I'm messing with. I have a CMIC PCI NVMe and nvme native multipathing enabled, and that can recreate the lockdep splat 100% of the time. It goes away with this patch. Non-multipath devices are harder to hit the lockdep splat for a different reason. >From 00dd7a573d3dd14be748b46e040bb5eb0f5687b1 Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Tue, 21 May 2024 06:41:45 -0700 Subject: [PATCH] nvme: switch rwsem to srcu Signed-off-by: Keith Busch --- drivers/nvme/host/core.c | 94 +++++++++++++++++++++-------------- drivers/nvme/host/ioctl.c | 12 ++--- drivers/nvme/host/multipath.c | 21 ++++---- drivers/nvme/host/nvme.h | 3 +- 4 files changed, 76 insertions(+), 54 deletions(-) diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 7706df2373494..480af74f1606e 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -3684,9 +3684,10 @@ static int nvme_init_ns_head(struct nvme_ns *ns, struct nvme_ns_info *info) struct nvme_ns *nvme_find_get_ns(struct nvme_ctrl *ctrl, unsigned nsid) { struct nvme_ns *ns, *ret = NULL; + int srcu_idx; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) { + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) { if (ns->head->ns_id == nsid) { if (!nvme_get_ns(ns)) continue; @@ -3696,7 +3697,7 @@ struct nvme_ns *nvme_find_get_ns(struct nvme_ctrl *ctrl, unsigned nsid) if (ns->head->ns_id > nsid) break; } - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); return ret; } EXPORT_SYMBOL_NS_GPL(nvme_find_get_ns, NVME_TARGET_PASSTHRU); @@ -3710,7 +3711,7 @@ static void nvme_ns_add_to_ctrl_list(struct nvme_ns *ns) list_for_each_entry_reverse(tmp, &ns->ctrl->namespaces, list) { if (tmp->head->ns_id < ns->head->ns_id) { - list_add(&ns->list, &tmp->list); + list_add_rcu(&ns->list, &tmp->list); return; } } @@ -3776,17 +3777,17 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, struct nvme_ns_info *info) if (nvme_update_ns_info(ns, info)) goto out_unlink_ns; - down_write(&ctrl->namespaces_rwsem); + mutex_lock(&ctrl->namespaces_lock); /* * Ensure that no namespaces are added to the ctrl list after the queues * are frozen, thereby avoiding a deadlock between scan and reset. */ if (test_bit(NVME_CTRL_FROZEN, &ctrl->flags)) { - up_write(&ctrl->namespaces_rwsem); + mutex_unlock(&ctrl->namespaces_lock); goto out_unlink_ns; } nvme_ns_add_to_ctrl_list(ns); - up_write(&ctrl->namespaces_rwsem); + mutex_unlock(&ctrl->namespaces_lock); nvme_get_ctrl(ctrl); if (device_add_disk(ctrl->device, ns->disk, nvme_ns_attr_groups)) @@ -3809,9 +3810,9 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, struct nvme_ns_info *info) out_cleanup_ns_from_list: nvme_put_ctrl(ctrl); - down_write(&ctrl->namespaces_rwsem); - list_del_init(&ns->list); - up_write(&ctrl->namespaces_rwsem); + mutex_lock(&ctrl->namespaces_lock); + list_del_rcu(&ns->list); + mutex_unlock(&ctrl->namespaces_lock); out_unlink_ns: mutex_lock(&ctrl->subsys->lock); list_del_rcu(&ns->siblings); @@ -3861,10 +3862,11 @@ static void nvme_ns_remove(struct nvme_ns *ns) nvme_cdev_del(&ns->cdev, &ns->cdev_device); del_gendisk(ns->disk); - down_write(&ns->ctrl->namespaces_rwsem); - list_del_init(&ns->list); - up_write(&ns->ctrl->namespaces_rwsem); + mutex_lock(&ns->ctrl->namespaces_lock); + list_del_rcu(&ns->list); + mutex_unlock(&ns->ctrl->namespaces_lock); + synchronize_srcu(&ns->ctrl->srcu); if (last_path) nvme_mpath_shutdown_disk(ns->head); nvme_put_ns(ns); @@ -3953,16 +3955,17 @@ static void nvme_remove_invalid_namespaces(struct nvme_ctrl *ctrl, struct nvme_ns *ns, *next; LIST_HEAD(rm_list); - down_write(&ctrl->namespaces_rwsem); + mutex_lock(&ctrl->namespaces_lock); list_for_each_entry_safe(ns, next, &ctrl->namespaces, list) { if (ns->head->ns_id > nsid) - list_move_tail(&ns->list, &rm_list); + list_splice_init_rcu(&ns->list, &rm_list, synchronize_rcu); } - up_write(&ctrl->namespaces_rwsem); + mutex_unlock(&ctrl->namespaces_lock); list_for_each_entry_safe(ns, next, &rm_list, list) nvme_ns_remove(ns); + synchronize_srcu(&ctrl->srcu); } static int nvme_scan_ns_list(struct nvme_ctrl *ctrl) @@ -4132,12 +4135,14 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl) /* this is a no-op when called from the controller reset handler */ nvme_change_ctrl_state(ctrl, NVME_CTRL_DELETING_NOIO); - down_write(&ctrl->namespaces_rwsem); - list_splice_init(&ctrl->namespaces, &ns_list); - up_write(&ctrl->namespaces_rwsem); + mutex_lock(&ctrl->namespaces_lock); + list_splice_init_rcu(&ctrl->namespaces, &ns_list, synchronize_rcu); + mutex_unlock(&ctrl->namespaces_lock); list_for_each_entry_safe(ns, next, &ns_list, list) nvme_ns_remove(ns); + + synchronize_srcu(&ctrl->srcu); } EXPORT_SYMBOL_GPL(nvme_remove_namespaces); @@ -4582,6 +4587,7 @@ static void nvme_free_ctrl(struct device *dev) key_put(ctrl->tls_key); nvme_free_cels(ctrl); nvme_mpath_uninit(ctrl); + cleanup_srcu_struct(&ctrl->srcu); nvme_auth_stop(ctrl); nvme_auth_free(ctrl); __free_page(ctrl->discard_page); @@ -4614,10 +4620,15 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev, ctrl->passthru_err_log_enabled = false; clear_bit(NVME_CTRL_FAILFAST_EXPIRED, &ctrl->flags); spin_lock_init(&ctrl->lock); + mutex_init(&ctrl->namespaces_lock); + + ret = init_srcu_struct(&ctrl->srcu); + if (ret) + return ret; + mutex_init(&ctrl->scan_lock); INIT_LIST_HEAD(&ctrl->namespaces); xa_init(&ctrl->cels); - init_rwsem(&ctrl->namespaces_rwsem); ctrl->dev = dev; ctrl->ops = ops; ctrl->quirks = quirks; @@ -4697,6 +4708,7 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev, out: if (ctrl->discard_page) __free_page(ctrl->discard_page); + cleanup_srcu_struct(&ctrl->srcu); return ret; } EXPORT_SYMBOL_GPL(nvme_init_ctrl); @@ -4705,22 +4717,24 @@ EXPORT_SYMBOL_GPL(nvme_init_ctrl); void nvme_mark_namespaces_dead(struct nvme_ctrl *ctrl) { struct nvme_ns *ns; + int srcu_idx; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) blk_mark_disk_dead(ns->disk); - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); } EXPORT_SYMBOL_GPL(nvme_mark_namespaces_dead); void nvme_unfreeze(struct nvme_ctrl *ctrl) { struct nvme_ns *ns; + int srcu_idx; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) blk_mq_unfreeze_queue(ns->queue); - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); clear_bit(NVME_CTRL_FROZEN, &ctrl->flags); } EXPORT_SYMBOL_GPL(nvme_unfreeze); @@ -4728,14 +4742,15 @@ EXPORT_SYMBOL_GPL(nvme_unfreeze); int nvme_wait_freeze_timeout(struct nvme_ctrl *ctrl, long timeout) { struct nvme_ns *ns; + int srcu_idx; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) { + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) { timeout = blk_mq_freeze_queue_wait_timeout(ns->queue, timeout); if (timeout <= 0) break; } - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); return timeout; } EXPORT_SYMBOL_GPL(nvme_wait_freeze_timeout); @@ -4743,23 +4758,25 @@ EXPORT_SYMBOL_GPL(nvme_wait_freeze_timeout); void nvme_wait_freeze(struct nvme_ctrl *ctrl) { struct nvme_ns *ns; + int srcu_idx; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) blk_mq_freeze_queue_wait(ns->queue); - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); } EXPORT_SYMBOL_GPL(nvme_wait_freeze); void nvme_start_freeze(struct nvme_ctrl *ctrl) { struct nvme_ns *ns; + int srcu_idx; set_bit(NVME_CTRL_FROZEN, &ctrl->flags); - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) blk_freeze_queue_start(ns->queue); - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); } EXPORT_SYMBOL_GPL(nvme_start_freeze); @@ -4802,11 +4819,12 @@ EXPORT_SYMBOL_GPL(nvme_unquiesce_admin_queue); void nvme_sync_io_queues(struct nvme_ctrl *ctrl) { struct nvme_ns *ns; + int srcu_idx; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) blk_sync_queue(ns->queue); - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); } EXPORT_SYMBOL_GPL(nvme_sync_io_queues); diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c index 499a8bb7cac7d..0f05058692b55 100644 --- a/drivers/nvme/host/ioctl.c +++ b/drivers/nvme/host/ioctl.c @@ -789,16 +789,16 @@ static int nvme_dev_user_cmd(struct nvme_ctrl *ctrl, void __user *argp, bool open_for_write) { struct nvme_ns *ns; - int ret; + int ret, srcu_idx; - down_read(&ctrl->namespaces_rwsem); + srcu_idx = srcu_read_lock(&ctrl->srcu); if (list_empty(&ctrl->namespaces)) { ret = -ENOTTY; goto out_unlock; } - ns = list_first_entry(&ctrl->namespaces, struct nvme_ns, list); - if (ns != list_last_entry(&ctrl->namespaces, struct nvme_ns, list)) { + ns = list_first_or_null_rcu(&ctrl->namespaces, struct nvme_ns, list); + if (!ns) { dev_warn(ctrl->device, "NVME_IOCTL_IO_CMD not supported when multiple namespaces present!\n"); ret = -EINVAL; @@ -808,14 +808,14 @@ static int nvme_dev_user_cmd(struct nvme_ctrl *ctrl, void __user *argp, dev_warn(ctrl->device, "using deprecated NVME_IOCTL_IO_CMD ioctl on the char device!\n"); kref_get(&ns->kref); - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); ret = nvme_user_cmd(ctrl, ns, argp, 0, open_for_write); nvme_put_ns(ns); return ret; out_unlock: - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); return ret; } diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index 1bee176fd850e..d8b6b4648eaff 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -151,16 +151,17 @@ void nvme_mpath_end_request(struct request *rq) void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl) { struct nvme_ns *ns; + int srcu_idx; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) { + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) { if (!ns->head->disk) continue; kblockd_schedule_work(&ns->head->requeue_work); if (nvme_ctrl_state(ns->ctrl) == NVME_CTRL_LIVE) disk_uevent(ns->head->disk, KOBJ_CHANGE); } - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); } static const char *nvme_ana_state_names[] = { @@ -194,13 +195,14 @@ bool nvme_mpath_clear_current_path(struct nvme_ns *ns) void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl) { struct nvme_ns *ns; + int srcu_idx; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) { + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) { nvme_mpath_clear_current_path(ns); kblockd_schedule_work(&ns->head->requeue_work); } - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); } void nvme_mpath_revalidate_paths(struct nvme_ns *ns) @@ -681,6 +683,7 @@ static int nvme_update_ana_state(struct nvme_ctrl *ctrl, u32 nr_nsids = le32_to_cpu(desc->nnsids), n = 0; unsigned *nr_change_groups = data; struct nvme_ns *ns; + int srcu_idx; dev_dbg(ctrl->device, "ANA group %d: %s.\n", le32_to_cpu(desc->grpid), @@ -692,8 +695,8 @@ static int nvme_update_ana_state(struct nvme_ctrl *ctrl, if (!nr_nsids) return 0; - down_read(&ctrl->namespaces_rwsem); - list_for_each_entry(ns, &ctrl->namespaces, list) { + srcu_idx = srcu_read_lock(&ctrl->srcu); + list_for_each_entry_rcu(ns, &ctrl->namespaces, list) { unsigned nsid; again: nsid = le32_to_cpu(desc->nsids[n]); @@ -706,7 +709,7 @@ static int nvme_update_ana_state(struct nvme_ctrl *ctrl, if (ns->head->ns_id > nsid) goto again; } - up_read(&ctrl->namespaces_rwsem); + srcu_read_unlock(&ctrl->srcu, srcu_idx); return 0; } diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h index fc31bd340a63a..a005941a8b67e 100644 --- a/drivers/nvme/host/nvme.h +++ b/drivers/nvme/host/nvme.h @@ -282,7 +282,8 @@ struct nvme_ctrl { struct blk_mq_tag_set *tagset; struct blk_mq_tag_set *admin_tagset; struct list_head namespaces; - struct rw_semaphore namespaces_rwsem; + struct mutex namespaces_lock; + struct srcu_struct srcu; struct device ctrl_device; struct device *device; /* char device */ #ifdef CONFIG_NVME_HWMON -- 2.43.0