From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 296E326AE5; Tue, 18 Aug 2026 07:08:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787036902; cv=none; b=bo4WSbXK2OKzAXh58hzH0NXoxik6FWLk3SoBbBl30v6m3aBfig4Act8nkr7zSHIw5xj6fCqVooHEk7n/rgfGu2Aj3MYkHVdR3c/9FTvpAIi9B4Aww9hDAJi0BGdu0BZh95AvMBB/hJhPnYKY+HrDkk+G9F66Ol4CsAVYfqm6w/8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787036902; c=relaxed/simple; bh=l/419XZXkAWDjlMDRws2++0fLyD0VDmz2P57GWPFBFo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oLiaPI6rl5NT+RD1N+dQsKo9P4ja7C2HpED9wPbBB7Lct6MTTeOQ4VJV45tGRrpRjARTS1J0MtC6Xb59I1/SqDWAlHleKkLIdDgbOlfzNZRvcHNoRW5+OmT+NtLa3dU4ukd0pco+WoXt3AgiD7N56tyUT58amkHtHuOlT2otFuU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gSCMDPJG; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gSCMDPJG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 290911F00A3A; Tue, 18 Aug 2026 07:08:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787036900; bh=OJWwT1pxPD5QyI83sGp5gqWWT9hcHXQl/xlvBToC+M4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gSCMDPJGbrCHu+5p6+1Yq0H+yk9h9W6iFybV4rFgnQno9h0F2tkL1xxTRCOXsbyhA fmyoBJQ/wWZDqrPaETcNPFbv1CNmX37EZoacfK5lSakac/i8jTsEQZ15jrp/Xz47l4 +ZlnWVQXnvyZH4Ytw+IJ3fsSHWNHnO0jdKdmuX53p92tR31iYhHk1W4pjOM/k0yqxc 6pmXx2dHtP5SPJHztg1sHsZ2/2n1tSe9hIv+SideG6NRMZZO7pxiuv+tjwnBCqN/a3 hYuRdhESoKBVH/etd/f7NfjXfj5tasjwDwoCy3u6UfraO+20hK+wae63kB59llewbG MOrvBAW2eCEQg== From: Yu Kuai To: Jens Axboe , Tejun Heo , Josef Bacik , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= Cc: Yu Kuai , Christoph Hellwig , Tao Cui , Jan Kara , Ming Lei , Jonathan Corbet , Shuah Khan , Coly Li , Kent Overstreet , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , Song Liu , Li Nan , Xiao Ni , Pankaj Gupta , Dan Williams , Vishal Verma , Dave Jiang , Alison Schofield , Ira Weiny , Andreas Gruenbacher , Matthew Wilcox , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, dm-devel@lists.linux.dev, linux-raid@vger.kernel.org, nvdimm@lists.linux.dev, virtualization@lists.linux.dev, gfs2@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v3 3/3] blk-cgroup: move async bio punt state to blkcg Date: Tue, 18 Aug 2026 15:06:41 +0800 Message-ID: <20260818070641.756747-4-yukuai@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260818070641.756747-1-yukuai@kernel.org> References: <20260818070641.756747-1-yukuai@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Yu Kuai blkcg_punt_bio_submit() currently queues punted bios on blkg->async_bios, so it has to call bio_blkg() to find or create a queue-local blkg. Bios now carry and pin the blkcg css, so punted bio lifetime no longer needs to be anchored by a blkg. Keeping the punt state in blkg can instantiate a blkg even when no blkcg policy is enabled, just to bounce submission from a shared kthread. Move async_bio_lock, async_bios and async_bio_work to struct blkcg, and queue punted bios on bio_blkcg() for non-root cgroups. Root or unassociated bios are submitted directly. This preserves the priority-inversion avoidance while preventing blkcg_punt_bio_submit() from creating blkgs that are not needed by any policy. Signed-off-by: Yu Kuai --- block/blk-cgroup.c | 44 +++++++++++++++++++++----------------------- block/blk-cgroup.h | 14 ++++++-------- 2 files changed, 27 insertions(+), 31 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index c3bbcb3e7e58..2c758c26bce6 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -178,14 +178,10 @@ static void blkg_free(struct blkcg_gq *blkg) static void __blkg_release(struct rcu_head *rcu) { struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head); -#ifdef CONFIG_BLK_CGROUP_PUNT_BIO - WARN_ON(!bio_list_empty(&blkg->async_bios)); -#endif - blkg_free(blkg); } /* * A group is RCU protected, but having an rcu lock does not mean that one @@ -224,23 +220,22 @@ static void blkg_release(struct percpu_ref *ref) } #ifdef CONFIG_BLK_CGROUP_PUNT_BIO static struct workqueue_struct *blkcg_punt_bio_wq; -static void blkg_async_bio_workfn(struct work_struct *work) +static void blkcg_async_bio_workfn(struct work_struct *work) { - struct blkcg_gq *blkg = container_of(work, struct blkcg_gq, - async_bio_work); + struct blkcg *blkcg = container_of(work, struct blkcg, async_bio_work); struct bio_list bios = BIO_EMPTY_LIST; struct bio *bio; struct blk_plug plug; bool need_plug = false; - /* as long as there are pending bios, @blkg can't go away */ - spin_lock(&blkg->async_bio_lock); - bio_list_merge_init(&bios, &blkg->async_bios); - spin_unlock(&blkg->async_bio_lock); + /* as long as there are pending bios, @blkcg can't go away */ + spin_lock(&blkcg->async_bio_lock); + bio_list_merge_init(&bios, &blkcg->async_bios); + spin_unlock(&blkcg->async_bio_lock); /* start plug only when bio_list contains at least 2 bios */ if (bios.head && bios.head->bi_next) { need_plug = true; blk_start_plug(&plug); @@ -257,19 +252,19 @@ static void blkg_async_bio_workfn(struct work_struct *work) * cgroup. Use this helper instead of submit_bio to punt the actual issuing to * a dedicated per-blkcg work item to avoid such priority inversions. */ void blkcg_punt_bio_submit(struct bio *bio) { - struct blkcg_gq *blkg = bio_blkg(bio); + struct blkcg *blkcg = bio_blkcg(bio); - if (blkg && blkg->parent) { - spin_lock(&blkg->async_bio_lock); - bio_list_add(&blkg->async_bios, bio); - spin_unlock(&blkg->async_bio_lock); - queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work); + if (blkcg && cgroup_parent(blkcg->css.cgroup)) { + spin_lock(&blkcg->async_bio_lock); + bio_list_add(&blkcg->async_bios, bio); + spin_unlock(&blkcg->async_bio_lock); + queue_work(blkcg_punt_bio_wq, &blkcg->async_bio_work); } else { - /* Never bounce if there is no non-root blkg to queue on. */ + /* Never bounce if there is no non-root blkcg to queue on. */ submit_bio(bio); } } EXPORT_SYMBOL_GPL(blkcg_punt_bio_submit); @@ -348,15 +343,10 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk, blkg->q = disk->queue; INIT_LIST_HEAD(&blkg->q_node); blkg->blkcg = blkcg; blkg->blkcg_id = blkcg->css.id; blkg->iostat.blkg = blkg; -#ifdef CONFIG_BLK_CGROUP_PUNT_BIO - spin_lock_init(&blkg->async_bio_lock); - bio_list_init(&blkg->async_bios); - INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn); -#endif u64_stats_init(&blkg->iostat.sync); for_each_possible_cpu(cpu) { u64_stats_init(&per_cpu_ptr(blkg->iostat_cpu, cpu)->sync); per_cpu_ptr(blkg->iostat_cpu, cpu)->blkg = blkg; @@ -1388,10 +1378,13 @@ static void blkcg_css_free(struct cgroup_subsys_state *css) if (blkcg->cpd[i]) blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]); mutex_unlock(&blkcg_pol_mutex); +#ifdef CONFIG_BLK_CGROUP_PUNT_BIO + WARN_ON(!bio_list_empty(&blkcg->async_bios)); +#endif free_percpu(blkcg->lhead); kfree(blkcg); } static struct cgroup_subsys_state * @@ -1436,10 +1429,15 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css) } spin_lock_init(&blkcg->lock); refcount_set(&blkcg->online_pin, 1); INIT_HLIST_HEAD(&blkcg->blkg_list); +#ifdef CONFIG_BLK_CGROUP_PUNT_BIO + spin_lock_init(&blkcg->async_bio_lock); + bio_list_init(&blkcg->async_bios); + INIT_WORK(&blkcg->async_bio_work, blkcg_async_bio_workfn); +#endif #ifdef CONFIG_CGROUP_WRITEBACK INIT_LIST_HEAD(&blkcg->cgwb_list); #endif list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs); diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index 936428b6127e..eb76cc38b41b 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -75,18 +75,11 @@ struct blkcg_gq { struct blkg_iostat_set __percpu *iostat_cpu; struct blkg_iostat_set iostat; struct blkg_policy_data *pd[BLKCG_MAX_POLS]; -#ifdef CONFIG_BLK_CGROUP_PUNT_BIO - spinlock_t async_bio_lock; - struct bio_list async_bios; -#endif - union { - struct work_struct async_bio_work; - struct work_struct free_work; - }; + struct work_struct free_work; atomic_t use_delay; atomic64_t delay_nsec; atomic64_t delay_start; u64 last_delay; @@ -111,10 +104,15 @@ struct blkcg { /* * List of updated percpu blkg_iostat_set's since the last flush. */ struct llist_head __percpu *lhead; +#ifdef CONFIG_BLK_CGROUP_PUNT_BIO + spinlock_t async_bio_lock; /* protects async_bios */ + struct bio_list async_bios; + struct work_struct async_bio_work; +#endif #ifdef CONFIG_BLK_CGROUP_FC_APPID char fc_app_id[FC_APPID_LEN]; #endif #ifdef CONFIG_CGROUP_WRITEBACK struct list_head cgwb_list; -- 2.51.0