From patchwork Thu Aug 15 19:57:50 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tejun Heo X-Patchwork-Id: 11096425 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 558BD1395 for ; Thu, 15 Aug 2019 19:57:55 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 439BB2898C for ; Thu, 15 Aug 2019 19:57:55 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 379DC2899C; Thu, 15 Aug 2019 19:57:55 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A98042898C for ; Thu, 15 Aug 2019 19:57:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730132AbfHOT5y (ORCPT ); Thu, 15 Aug 2019 15:57:54 -0400 Received: from mail-qk1-f196.google.com ([209.85.222.196]:43857 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728956AbfHOT5x (ORCPT ); Thu, 15 Aug 2019 15:57:53 -0400 Received: by mail-qk1-f196.google.com with SMTP id m2so2801865qkd.10; Thu, 15 Aug 2019 12:57:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=NK0PK6csvakTjylMz8jDV7zgrirY2g6A6SS9gcMGP38=; b=XEiIETwR/iRc/lXiBJkeGJWLPwdP3OTZNZTIZNNbaUyYnuuBUMWk76hAjCesVsGRvR DVIXJNeKmQfqKXW702SF1PUeP9sMQBQHvirBaKtwjRZq+JeR2Bqiqj8abtcJSMCd1jzQ 70f4yD1051JXCEGH8Jf4XgvdEGl7z6LtJqxDO8gRemoNlh+IeCfl8mEaqjzVNU4JR8CL rQRPxZoa84hi4tZtGQDIy5KO8uZu8JaNvj9NPih9o3iaXsNOSBCo6teWiZ/GbCdlfiuX p4mSuilXdKhg1WbG1k1KNt5O/wZddMSeF2o9jyOlaEWhRejaiNoKnop+vbB73UpmszkK DYkw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=NK0PK6csvakTjylMz8jDV7zgrirY2g6A6SS9gcMGP38=; b=JSiPhVl6cYU2AppTF3Y2khVQgFb1256EC58comULgg8Pw2ubbLCeu2O8q4raJra8pr mJIIdAxaYLmCQshCImx+biolu6tsKPx/7JMBEiEWjD2yyoY+KCYTStjobiUb8ewyI7Lf 6CeiMbLxINoNNIqn6l6hbuQCRnHWROkfLTD5LEyXvCyufvy9Y48c7/+3nyXhDtrgbFFI pkZfJzcGXrCUKeLiA51DeZF99+HepuSRXejBDbNVBsSAchVN7cVnkAcDV06F6XqonD52 fsvZR6GLJXIRhqBebAMUl4JJnPOyasUeT09irldpufzItqnPWFGgRqPTYTkMjNaUG9Nw vWUQ== X-Gm-Message-State: APjAAAVpDnWertv07XkjopAyu0WuhotGztzmfczwjyJlDykxBd2ub1ew r1RPG7CEbtw4BAhk3XZxXUQ= X-Google-Smtp-Source: APXvYqxgqkXzG03UW+nQ2wzQV8lJWn1lUi6WbNWPWMtyk1a9ytxbt9vAVv4HDVD3hmWenqlqAUYrlw== X-Received: by 2002:ae9:e411:: with SMTP id q17mr5416347qkc.465.1565899072231; Thu, 15 Aug 2019 12:57:52 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::1:25cd]) by smtp.gmail.com with ESMTPSA id o21sm1768914qkk.100.2019.08.15.12.57.51 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 15 Aug 2019 12:57:51 -0700 (PDT) Date: Thu, 15 Aug 2019 12:57:50 -0700 From: Tejun Heo To: axboe@kernel.dk, jack@suse.cz, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, guro@fb.com, akpm@linux-foundation.org Subject: [PATCH 2/5] bdi: Add bdi->id Message-ID: <20190815195750.GC2263813@devbig004.ftw2.facebook.com> References: <20190815195619.GA2263813@devbig004.ftw2.facebook.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190815195619.GA2263813@devbig004.ftw2.facebook.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP There currently is no way to universally identify and lookup a bdi without holding a reference and pointer to it. This patch adds an non-recycling bdi->id and implements bdi_get_by_id() which looks up bdis by their ids. This will be used by memcg foreign inode flushing. I left bdi_list alone for simplicity and because while rb_tree does support rcu assignment it doesn't seem to guarantee lossless walk when walk is racing aginst tree rebalance operations. Signed-off-by: Tejun Heo Reviewed-by: Jan Kara --- include/linux/backing-dev-defs.h | 2 + include/linux/backing-dev.h | 1 mm/backing-dev.c | 65 +++++++++++++++++++++++++++++++++++++-- 3 files changed, 66 insertions(+), 2 deletions(-) --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -185,6 +185,8 @@ struct bdi_writeback { }; struct backing_dev_info { + u64 id; + struct rb_node rb_node; /* keyed by ->id */ struct list_head bdi_list; unsigned long ra_pages; /* max readahead in PAGE_SIZE units */ unsigned long io_pages; /* max allowed IO size */ --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -24,6 +24,7 @@ static inline struct backing_dev_info *b return bdi; } +struct backing_dev_info *bdi_get_by_id(u64 id); void bdi_put(struct backing_dev_info *bdi); __printf(2, 3) --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0-only #include +#include #include #include #include @@ -22,10 +23,12 @@ EXPORT_SYMBOL_GPL(noop_backing_dev_info) static struct class *bdi_class; /* - * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side - * locking. + * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU + * reader side locking. */ DEFINE_SPINLOCK(bdi_lock); +static u64 bdi_id_cursor; +static struct rb_root bdi_tree = RB_ROOT; LIST_HEAD(bdi_list); /* bdi_wq serves all asynchronous writeback tasks */ @@ -859,9 +862,58 @@ struct backing_dev_info *bdi_alloc_node( } EXPORT_SYMBOL(bdi_alloc_node); +static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp) +{ + struct rb_node **p = &bdi_tree.rb_node; + struct rb_node *parent = NULL; + struct backing_dev_info *bdi; + + lockdep_assert_held(&bdi_lock); + + while (*p) { + parent = *p; + bdi = rb_entry(parent, struct backing_dev_info, rb_node); + + if (bdi->id > id) + p = &(*p)->rb_left; + else if (bdi->id < id) + p = &(*p)->rb_right; + else + break; + } + + if (parentp) + *parentp = parent; + return p; +} + +/** + * bdi_get_by_id - lookup and get bdi from its id + * @id: bdi id to lookup + * + * Find bdi matching @id and get it. Returns NULL if the matching bdi + * doesn't exist or is already unregistered. + */ +struct backing_dev_info *bdi_get_by_id(u64 id) +{ + struct backing_dev_info *bdi = NULL; + struct rb_node **p; + + spin_lock_bh(&bdi_lock); + p = bdi_lookup_rb_node(id, NULL); + if (*p) { + bdi = rb_entry(*p, struct backing_dev_info, rb_node); + bdi_get(bdi); + } + spin_unlock_bh(&bdi_lock); + + return bdi; +} + int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args) { struct device *dev; + struct rb_node *parent, **p; if (bdi->dev) /* The driver needs to use separate queues per device */ return 0; @@ -877,7 +929,15 @@ int bdi_register_va(struct backing_dev_i set_bit(WB_registered, &bdi->wb.state); spin_lock_bh(&bdi_lock); + + bdi->id = ++bdi_id_cursor; + + p = bdi_lookup_rb_node(bdi->id, &parent); + rb_link_node(&bdi->rb_node, parent, p); + rb_insert_color(&bdi->rb_node, &bdi_tree); + list_add_tail_rcu(&bdi->bdi_list, &bdi_list); + spin_unlock_bh(&bdi_lock); trace_writeback_bdi_register(bdi); @@ -918,6 +978,7 @@ EXPORT_SYMBOL(bdi_register_owner); static void bdi_remove_from_list(struct backing_dev_info *bdi) { spin_lock_bh(&bdi_lock); + rb_erase(&bdi->rb_node, &bdi_tree); list_del_rcu(&bdi->bdi_list); spin_unlock_bh(&bdi_lock);