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 EE362D20693 for ; Wed, 16 Oct 2024 03:38:04 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:References:Cc:To:From:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=oWxECMca74WLPsmqhLVotQu3G4fMeZsdvp9eijNM/gM=; b=dpb2B23TSOHdGgtzcu28CTUN0M IVDPDIWz8+GhkwZr7Gn8hERUr+L0N3FNmniSj4wxQIdwg1DeMb6rTqFwh2gyRXIi9DK1tuVVpKvpV 6TWpM9zVVxUXfNSBobFaBqo/6rJtR+11ZCaNo2CDoorfIOIO4TFdGnUvmcEY0rPRQBjyyoeULzQa1 4zzbj6VdKFgI57kaqP48APVnUeQ4L2aDLbQQ3f/GK2HyFhMexHQgiXwC6JL8JOiUzbKVaWnNJ8UXw oHjkh9/uezxoCglL4tCvQ14BVpd9xEikh6ExOg8hCSiiGACTvvArGxGrdOELaZpDBBaFspmSSYANh 6dPwsrYA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t0urI-0000000AMvK-3TOJ; Wed, 16 Oct 2024 03:38:00 +0000 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t0urF-0000000AMuo-46d6 for linux-nvme@lists.infradead.org; Wed, 16 Oct 2024 03:37:59 +0000 Received: from pps.filterd (m0360083.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 49G2snJs005147; Wed, 16 Oct 2024 03:37:53 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=oWxECM ca74WLPsmqhLVotQu3G4fMeZsdvp9eijNM/gM=; b=JdoOSiUaSd97u28Tx4UtDv HUNEwduRQGKTd4z3BLpyjJnKH7s3Pjw50fJYxZhuX8y+P6JDp9nDLXI2IP9U24zv l0QHUAr3y7nqEQcWVPSEFoMi+g+5GfAT8SYs5wUHLeNelkzYPD1S+FrD7lHqzfmu h5wCDkzBYG0AC/vGbw/P56BzzRwz8ebMp4cbE4XyUfQUn1tFJgF+EMcr8VrMigqj O0dMVsGzdZ25m78sRQ6iUq4gXI/yx6CjJccXxaqxjxkskqwBht3ocFH+6wib6tLW zI0ZJtyg2eXuwegrI0oVSPmVpGBr8YLuLJWk+qVtV+8b9btpFWN/RCOoghPeeD2Q == Received: from ppma13.dal12v.mail.ibm.com (dd.9e.1632.ip4.static.sl-reverse.com [50.22.158.221]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 42a54dg3te-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 16 Oct 2024 03:37:52 +0000 (GMT) Received: from pps.filterd (ppma13.dal12v.mail.ibm.com [127.0.0.1]) by ppma13.dal12v.mail.ibm.com (8.18.1.2/8.18.1.2) with ESMTP id 49FNWika005377; Wed, 16 Oct 2024 03:19:14 GMT Received: from smtprelay03.wdc07v.mail.ibm.com ([172.16.1.70]) by ppma13.dal12v.mail.ibm.com (PPS) with ESMTPS id 4285nj6tde-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 16 Oct 2024 03:19:14 +0000 Received: from smtpav05.dal12v.mail.ibm.com (smtpav05.dal12v.mail.ibm.com [10.241.53.104]) by smtprelay03.wdc07v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 49G3JD0J22479584 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 16 Oct 2024 03:19:14 GMT Received: from smtpav05.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C798658067; Wed, 16 Oct 2024 03:19:13 +0000 (GMT) Received: from smtpav05.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 32F1358056; Wed, 16 Oct 2024 03:19:10 +0000 (GMT) Received: from [9.171.76.114] (unknown [9.171.76.114]) by smtpav05.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 16 Oct 2024 03:19:09 +0000 (GMT) Message-ID: <2476d00b-35d3-4516-b76c-9b76a499e4fc@linux.ibm.com> Date: Wed, 16 Oct 2024 08:49:08 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv4 RFC 1/1] nvme-multipath: Add sysfs attributes for showing multipath info From: Nilay Shroff To: Hannes Reinecke , linux-nvme@lists.infradead.org Cc: dwagner@suse.de, hch@lst.de, kbusch@kernel.org, sagi@grimberg.me, axboe@fb.com, gjoyce@linux.ibm.com References: <20240911062653.1060056-1-nilay@linux.ibm.com> <20240911062653.1060056-4-nilay@linux.ibm.com> <5050777a-2812-4fcf-bed9-00f0cb5706fc@suse.de> <93af0dc5-c988-423c-9788-e93ca8703fd5@linux.ibm.com> <0f4528f0-8ef3-449f-bb15-47878d93a002@suse.de> <48bf8a1d-3a47-4c94-8cd0-7d8c4ea5d3ab@linux.ibm.com> Content-Language: en-US In-Reply-To: <48bf8a1d-3a47-4c94-8cd0-7d8c4ea5d3ab@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 93hur8SKxQNf_xoHnEc3z70IaNtAUyX_ X-Proofpoint-ORIG-GUID: 93hur8SKxQNf_xoHnEc3z70IaNtAUyX_ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 phishscore=0 mlxlogscore=999 lowpriorityscore=0 suspectscore=0 bulkscore=0 spamscore=0 malwarescore=0 clxscore=1015 mlxscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410160021 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241015_203758_163274_3E67DB46 X-CRM114-Status: GOOD ( 27.99 ) 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 Hi Hannes, On 10/7/24 21:03, Nilay Shroff wrote: > > > On 10/7/24 19:34, Hannes Reinecke wrote: >> On 10/7/24 15:47, Nilay Shroff wrote: >>> >>> >>> On 10/7/24 15:44, Hannes Reinecke wrote: >>>> On 9/11/24 08:26, Nilay Shroff wrote: >>>>> NVMe native multipath supports different IO policies for selecting I/O >>>>> path, however we don't have any visibility about which path is being >>>>> selected by multipath code for forwarding I/O. >>>>> This patch helps add that visibility by adding new sysfs attribute files >>>>> named "numa_nodes" and "queue_depth" under each namespace block device >>>>> path /sys/block/nvmeXcYnZ/. We also create a "multipath" sysfs directory >>>>> under head disk node and then from this directory add a link to each >>>>> namespace path device this head disk node points to. >>>>> >>>>> For instance, /sys/block/nvmeXnY/multipath/ would create a soft link to >>>>> each path the head disk node points to: >>>>> >>>>> $ ls -1 /sys/block/nvme1n1/ >>>>> nvme1c1n1 -> ../../../../../pci052e:78/052e:78:00.0/nvme/nvme1/nvme1c1n1 >>>>> nvme1c3n1 -> ../../../../../pci058e:78/058e:78:00.0/nvme/nvme3/nvme1c3n1 >>>>> >>>>> For round-robin I/O policy, we could easily infer from the above output >>>>> that I/O workload targeted to nvme3n1 would toggle across paths nvme1c1n1 >>>>> and nvme1c3n1. >>>>> >>>>> For numa I/O policy, the "numa_nodes" attribute file shows the numa nodes >>>>> being preferred by the respective block device path. The numa nodes value >>>>> is comma delimited list of nodes or A-B range of nodes. >>>>> >>>>> For queue-depth I/O policy, the "queue_depth" attribute file shows the >>>>> number of active/in-flight I/O requests currently queued for each path. >>>>> >>>>> Signed-off-by: Nilay Shroff >>>>> --- >>>>>    drivers/nvme/host/core.c      |  3 ++ >>>>>    drivers/nvme/host/multipath.c | 71 +++++++++++++++++++++++++++++++++++ >>>>>    drivers/nvme/host/nvme.h      | 20 ++++++++-- >>>>>    drivers/nvme/host/sysfs.c     | 20 ++++++++++ >>>>>    4 files changed, 110 insertions(+), 4 deletions(-) >>>>> >>>>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c >>>>> index 983909a600ad..6be29fd64236 100644 >>>>> --- a/drivers/nvme/host/core.c >>>>> +++ b/drivers/nvme/host/core.c >>>>> @@ -3951,6 +3951,9 @@ static void nvme_ns_remove(struct nvme_ns *ns) >>>>>          if (!nvme_ns_head_multipath(ns->head)) >>>>>            nvme_cdev_del(&ns->cdev, &ns->cdev_device); >>>>> + >>>>> +    nvme_mpath_remove_sysfs_link(ns); >>>>> + >>>>>        del_gendisk(ns->disk); >>>>>          mutex_lock(&ns->ctrl->namespaces_lock); >>>>> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c >>>>> index 518e22dd4f9b..7d9c36a7a261 100644 >>>>> --- a/drivers/nvme/host/multipath.c >>>>> +++ b/drivers/nvme/host/multipath.c >>>>> @@ -654,6 +654,8 @@ static void nvme_mpath_set_live(struct nvme_ns *ns) >>>>>            nvme_add_ns_head_cdev(head); >>>>>        } >>>>>    +    nvme_mpath_add_sysfs_link(ns); >>>>> + >>>>>        mutex_lock(&head->lock); >>>>>        if (nvme_path_is_optimized(ns)) { >>>>>            int node, srcu_idx; >>>> Nearly there. >>> Thank you for your review comments! >>> >>>> >>>> You can only call 'nvme_mpath_add_sysfs_link()' if the gendisk on the head had been created. >>>> >>>> And there is one branch in nvme_mpath_add_disk(): >>>> >>>>                  if (desc.state) { >>>>                          /* found the group desc: update */ >>>>                          nvme_update_ns_ana_state(&desc, ns); >>>> >>>> which does not go via nvme_mpath_set_live(), yet a device link would need to be create here, too. >>>> But you can't call nvme_mpath_add_sysfs_link() from nvme_mpath_add_disk(), as the actual gendisk >>>> might only be created later on during ANA log parsing.>> >>>> It is a tangle, and I haven't found a good way out of this. >>>> But I am _very much_ in favour of having these links, so please >>>> update your patch. >>>> In case disk supports ANA group then yes it would go through nvme_mpath_add_disk()->nvme_update_ns_ana_state(); >>>> and later nvme_update_ns_ana_state() would also fall through function nvme_mpath_set_live where we call >>>> nvme_mpath_add_sysfs_link(). >>> >>> So I think that in any case while multipath namespace is being created it has to go through >>> nvme_mpath_set_live function. And as we see in nvme_mpath_set_live function, we only create >>> sysfs link after the gendisk on the head is created. Do you agree with this? Or please let >>> me know if you have any further question. >>> >> But it doesn't: >> >>         if (nvme_state_is_live(ns->ana_state) && >>             nvme_ctrl_state(ns->ctrl) == NVME_CTRL_LIVE) >>                 nvme_mpath_set_live(ns); >> >> so if a namespace is being created for which nvme_state_is_live() returns 'false' nvme_mpath_set_live() is not called, and no links are being created. >> This can happen eg. if the first namespace to be encountered is in any other state than 'optimized' or 'non-optimized'. >> > > OK I got what you're suggesting here. So in this particular case when ANA state of a shared namespace > is neither "optimized" nor "non-optimized", we would have gendisk for shared namepspace (i.e. > nvmeXcYnZ) created but we don't have yet gendisk for corresponding head node (i.e. nvmeXnY) created. > So without the gendisk for head node created, how could we create a link from it to the namespace node? > > The link from gendisk head node would be eventually created when the ANA state of the namespace transition > to "optimized" or "non-optimized" state. I think, it's not anyways possible to have multipathing function > enabled until the gendisk for the head node created, isn't it? So I don't yet understand why do we really > need device link created if we don't have gendisk for head not ready? Am I missing anything here? > >> Cheers, >> >> Hannes > A gentle ping about this thread. Does change look okay or you have further comments? Am I missing something here? If so, can you please help me with it? Thanks, --Nilay