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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68C3CC433E0 for ; Thu, 11 Jun 2020 14:34:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4AA222072F for ; Thu, 11 Jun 2020 14:34:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728243AbgFKOe1 (ORCPT ); Thu, 11 Jun 2020 10:34:27 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2303 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728193AbgFKOe1 (ORCPT ); Thu, 11 Jun 2020 10:34:27 -0400 Received: from lhreml724-chm.china.huawei.com (unknown [172.18.7.106]) by Forcepoint Email with ESMTP id 827081DD25A8BE449D66; Thu, 11 Jun 2020 15:34:25 +0100 (IST) Received: from [127.0.0.1] (10.210.169.30) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1913.5; Thu, 11 Jun 2020 15:34:23 +0100 Subject: Re: [PATCH RFC v7 07/12] blk-mq: Add support in hctx_tags_bitmap_show() for a shared sbitmap To: Hannes Reinecke , , , , , , , , , , , CC: , , , , References: <1591810159-240929-1-git-send-email-john.garry@huawei.com> <1591810159-240929-8-git-send-email-john.garry@huawei.com> <9f4741c5-d117-d764-cf3a-a57192a788c3@suse.de> From: John Garry Message-ID: Date: Thu, 11 Jun 2020 15:33:04 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <9f4741c5-d117-d764-cf3a-a57192a788c3@suse.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.210.169.30] X-ClientProxiedBy: lhreml713-chm.china.huawei.com (10.201.108.64) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org >> +static int hctx_tags_shared_sbitmap_bitmap_show(void *data, struct >> seq_file *m) >> +{ >> +    struct blk_mq_hw_ctx *hctx = data; >> +    struct request_queue *q = hctx->queue; >> +    struct blk_mq_tag_set *set = q->tag_set; >> +    struct sbitmap shared_sb, *sb; >> +    int res; >> + >> +    if (!set) >> +        return 0; >> + >> +    /* >> +     * We could use the allocated sbitmap for that hctx here, but >> +     * that would mean that we would need to clean it prior to use. >> +     */ * >> +    res = sbitmap_init_node(&shared_sb, >> +                set->__bitmap_tags.sb.depth, >> +                set->__bitmap_tags.sb.shift, >> +                GFP_KERNEL, NUMA_NO_NODE); >> +    if (res) >> +        return res; >> +    sb = &shared_sb; >> + >> +    res = mutex_lock_interruptible(&q->sysfs_lock); >> +    if (res) >> +        goto out; >> +    if (hctx->tags) { >> +        hctx_filter_sb(sb, hctx); >> +        sbitmap_bitmap_show(sb, m); >> +    } >> + >> +    mutex_unlock(&q->sysfs_lock); >> + >> +out: >> +    sbitmap_free(&shared_sb); >> +    return res; >> +} >> + >>   static int hctx_tags_bitmap_show(void *data, struct seq_file *m) >>   { >>       struct blk_mq_hw_ctx *hctx = data; >> @@ -823,6 +884,7 @@ static const struct blk_mq_debugfs_attr >> blk_mq_debugfs_hctx_shared_sbitmap_attrs >>       {"busy", 0400, hctx_busy_show}, >>       {"ctx_map", 0400, hctx_ctx_map_show}, >>       {"tags", 0400, hctx_tags_show}, >> +    {"tags_bitmap", 0400, hctx_tags_shared_sbitmap_bitmap_show}, >>       {"sched_tags", 0400, hctx_sched_tags_show}, >>       {"sched_tags_bitmap", 0400, hctx_sched_tags_bitmap_show}, >>       {"io_poll", 0600, hctx_io_poll_show, hctx_io_poll_write}, >> > Ah, right. Here it is. > > But I don't get it; why do we have to allocate a temporary bitmap and > can't walk the existing shared sbitmap? For the bitmap dump - sbitmap_bitmap_show() - it is passed a struct sbitmap *. So we have to filter into a temp per-hctx struct sbitmap. We could change sbitmap_bitmap_show() to accept a filter iterator - which I think you're getting at - but I am not sure it's worth the change. Or else use the allocated sbitmap for the hctx, as above*, but I may be remove that (see 4/12 response). Cheers, John