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b=IAwWiY7Deif7+Op6gb6GTVrcArdtHpbZNbaSOIvOLfg6xNsYUstfjsHxncwqEtpfl QLB+whWLHYdrRa0XmEoYUgIakQ72eSVY/qdZErsXoAIWvfs6KmDM3fdiX2gm9Ov4hy ntu71EE3AAu0PcI3ZCImhPon24ne5FPDnPVuEEJZOnJvLytoTHvkQY1qaqNYNUN1er UOu9VQwtWOG4Om8WSjVYir9knzzfaf1GUkJKbfj3qPoKbx5E4Aq67QCPLdhnCyNTF1 opEYoRB3bzAQMyYxtaF1HHsVaSX0js+vBicMtWeMmAzZ7GU0pWjqQgHpRLKogLEJmM 4C+DutKsVjfAA== From: Yu Kuai To: Jens Axboe , Josef Bacik , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Jonathan Corbet , Shuah Khan , Randy Dunlap , Coly Li , Kent Overstreet , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , Song Liu , Li Nan , Xiao Ni , Andreas Gruenbacher , Matthew Wilcox , Jan Kara , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt Cc: Yu Kuai , Christoph Hellwig , Nilay Shroff , Tao Cui , linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org, dm-devel@lists.linux.dev, linux-raid@vger.kernel.org, gfs2@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev Subject: [PATCH v3 3/3] blk-cgroup: move async bio punt state to blkcg Date: Fri, 18 Sep 2026 12:17:44 +0800 Message-ID: <20260918041744.1526924-4-yukuai@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260918041744.1526924-1-yukuai@kernel.org> References: <20260918041744.1526924-1-yukuai@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 405F580005 X-Stat-Signature: rm8ictjn8tr9tq5ssukgu4wrtut397iy X-Rspam-User: X-HE-Tag: 1789705110-981592 X-HE-Meta: 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 CuijLUI9 LSko+v8u6TKN/KE1aHYlcZDQ+9+tW8wL3dTcpGX2XWcWSG8xeGtozR4bq7pxqP7u8W8iw4y3IKfJJitl4V+3pyDDzKGMdZrxJcxgA0jrxVnxWIzUO5nMI87uxg3BAI6wfRG8sJtJAct+NSKdz/Z49glV027DHXX5W3KKaqk0f4xI4w6iynp6N+7Ld9NN9rUOpqfTrP6RopYFGx2rupjPDVXOVOQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 | 40 +++++++++++++++++----------------------- block/blk-cgroup.h | 14 ++++++-------- 2 files changed, 23 insertions(+), 31 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 59ccfefe16a8..32e82880893b 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -180,14 +180,10 @@ 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 @@ -226,23 +222,22 @@ 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); @@ -259,19 +254,19 @@ 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); @@ -350,15 +345,10 @@ 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; @@ -1447,10 +1437,14 @@ 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); + 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 f68ea21958f5..7fee8555e713 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; + struct bio_list async_bios __guarded_by(&async_bio_lock); + 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