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b=Iczf3uijRgzjcA6B/j/Tqrmvx+RsfZ3ic3oyBMPLcYvnCHOsXKyP9Uc1mt+/kKnnw aCg+5WRQK3xX+vxyURFmuUZHcSElN7klIvjPQE6mDsVw1YZ5AFDf1AAtA0XwzjL8wn +V2QyfyO6vno/fnpnsGTHl2ZEAO2dG8ITTJty28KpY7y6myWHuzx9uKF6XML/6ocWn xvqP6MKXEWsqi/kbkY12AbVGGUnwkZKeU30q1clDS3JVvAqF5/4amoYAcBdl8PAJcy L5zGAiYTsbSph5NkP7VwbiyncINSGTTNYAtDbuitLlkDswP1sKH01tBnohL9UMffqh dcTwXOi8G8ajw== 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 v2 4/4] blk-cgroup: move async bio punt state to blkcg Date: Tue, 11 Aug 2026 14:47:44 +0800 Message-ID: <20260811064744.1139446-5-yukuai@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260811064744.1139446-1-yukuai@kernel.org> References: <20260811064744.1139446-1-yukuai@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 1FDC0C000A X-Stat-Signature: cp7dihitbczenng6pbs4nbdkjd5e6pf8 X-HE-Tag: 1786431104-59339 X-HE-Meta: U2FsdGVkX1+0g5D5L7oM1gbJgSmlY3RuPDj5ZxeNCbmvZk07dR52StHmBWtHOgNjAbVhksR73zzpDq9Y10kWdM/512yNiiqZBX2gPsdQ4Xvf0hL1zr8A0/HZ79B12MGqQMwAc6O0QXrQTTc+7xWfgqSpvhmZeR/1I72RWvT1x6CAxZhgltdiS3Mm3dAsSnE09gxCLRI+3oaXbL8BZ+gjIXA83vIL5oD/Ks27v50D7d1VJRCUGnPRBLHpTkYKDekdL+F+7guIdBilWO53m7+Kvg4rGlMD57obLM4EGxw/Ls5jC7+SCF/2HBFe1fl6bfwHbz89ZWCoULfNef/1F0UeAwEfgJKj4EjDiLZOPAcEZCPmII2/j7uxg3sS69EyQucJga3xUs04MHxaaBaiehw4lhTqIkgR4de6AWVDM6YUdHBUREC6fWzcbXM7wlm23xaZdM7S4MUDQ6Pxz5YkeTwkPNAmQEWDnwFTRgg2tkt+uLmT3rXKmJ8fDAfJ5UT97UuXUkTITIoToFQb6rKlPOe1wMnjirMzzquPO00to0UzFCYOIfvUmvPw0K70lj+7XNP6j2ywAJdDtg1mHFdx+itaoxd3e8PJD2CQtdgX8ZYe/vuAAfYKAHGTur36JaYlO2YmN8yw5Pl7wVVqKUVLoC0hnxhTJM5GNdkbe6df1QX1kFs7qIOHK7CQE51sv1shKBDSN1mGp2iGJ9KsAE7tn7VziL0W9rD8ePF1dwB1iqc8oNrijBG561GxWLwRVBCR3MVZ+QKFu8/MU4815AODa8krGTBZL29z0eyfVAYDnDZ95myiW28uzYDIn0PmEUZi6BZQkB+dKR6k15IAtr/azTqRufMIVhJJib205FM7m2c/x5ztxvafGH9JIm7yuOsPjbAZJ0dT18J6UbA2wG6wPcrcyWL9t5VVSZ4UL74Nr+gu9wBcNLKXdpQuPgm7NAzisU+2TP7SaBqc6zKAutgaBS2 mMbrMfUQ llo1gUMsIOguimQ4ooeLPoMz23h5Bgi/2cpHcAvdPdux5Nu6ZDcqysUiLiFIHrvT/QY8JLYh4GNIz8RhT4jUsC1MewyWbnbWoWC9dXGPyFkWS9fClBsU13UXdLMnXmGHxhvpF8gcBGBJC1CQVytwxvn7oLOlDr0YnLxqTmps5LwjpXGvp9esPGUv2EeHtIth4VLoyLpEJHesz1iHjDCBja3srx3yFdjm2ZfkhN/sQoNGsEdTQzuG85xL6Pg7eQ6atF9gQ+VpybTUzDuDGVEboMpioVSG29or5v2yI 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 | 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 1de2f2433d11..e76e9a52f95d 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -177,14 +177,10 @@ 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 @@ -218,23 +214,22 @@ 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); @@ -251,19 +246,19 @@ 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); @@ -342,15 +337,10 @@ 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; @@ -1370,10 +1360,13 @@ 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 * @@ -1418,10 +1411,15 @@ 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 3d113f6f6d25..efef0967d39e 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -74,18 +74,11 @@ 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; @@ -110,10 +103,15 @@ 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