From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Williams, Dan J" Subject: Re: [PATCH 08/15] block, dax, pmem: reference counting infrastructure Date: Fri, 25 Sep 2015 21:08:59 +0000 Message-ID: <1443215335.19562.1.camel@intel.com> References: <20150923043737.36490.70547.stgit@dwillia2-desk3.jf.intel.com> <20150923044155.36490.2017.stgit@dwillia2-desk3.jf.intel.com> <20150924151503.GF24375@infradead.org> <20150925113206.GA22272@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Cc: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "ross.zwisler@linux.intel.com" , "linux-fsdevel@vger.kernel.org" , "akpm@linux-foundation.org" , "axboe@kernel.dk" , "linux-nvdimm@ml01.01.org" To: "hch@infradead.org" Return-path: Received: from mga03.intel.com ([134.134.136.65]:25405 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933224AbbIYVJA (ORCPT ); Fri, 25 Sep 2015 17:09:00 -0400 In-Reply-To: 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vger.kernel.org via listexpand id S933323AbbIYVJE (ORCPT ); Fri, 25 Sep 2015 17:09:04 -0400 Received: from mga03.intel.com ([134.134.136.65]:25405 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933224AbbIYVJA (ORCPT ); Fri, 25 Sep 2015 17:09:00 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,588,1437462000"; d="scan'208";a="777289759" From: "Williams, Dan J" To: "hch@infradead.org" CC: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "ross.zwisler@linux.intel.com" , "linux-fsdevel@vger.kernel.org" , "akpm@linux-foundation.org" , "axboe@kernel.dk" , "linux-nvdimm@ml01.01.org" Subject: Re: [PATCH 08/15] block, dax, pmem: reference counting infrastructure Thread-Topic: [PATCH 08/15] block, dax, pmem: reference counting infrastructure Thread-Index: AQHQ9br7jLJH/VSMDUeQCRXK2tFlCZ5MQXWAgACTlwCAAMBzAIAAoSmA Date: Fri, 25 Sep 2015 21:08:59 +0000 Message-ID: <1443215335.19562.1.camel@intel.com> References: <20150923043737.36490.70547.stgit@dwillia2-desk3.jf.intel.com> <20150923044155.36490.2017.stgit@dwillia2-desk3.jf.intel.com> <20150924151503.GF24375@infradead.org> <20150925113206.GA22272@infradead.org> In-Reply-To: <20150925113206.GA22272@infradead.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.22.254.139] Content-Type: text/plain; charset="utf-8" Content-ID: MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id t8PL9ABv032054 On Fri, 2015-09-25 at 04:32 -0700, Christoph Hellwig wrote: > On Thu, Sep 24, 2015 at 05:03:18PM -0700, Dan Williams wrote: > > That makes sense to me, especially because drivers/nvdimm/blk.c is > > broken in the same way as drivers/nvdimm/pmem.c and it would be > > awkward to have it use blk_dax_get() / blk_dax_put(). The > > percpu_refcount should be valid for all queues and it will only ever > > be > 1 in the blk_mq and libnvdimm cases (for now). Will fix. > > Looking at this a bit more it might actually make sense to grab the > referene in common code before calling into ->make_request. > > Jens, any opinion on that? ...this works for me: 8<----- Subject: [PATCH] block: generic request_queue reference counting Allow pmem, and other synchronous/bio-based block drivers, to fallback on a per-cpu reference count managed by the core for tracking queue live/dead state. The existing per-cpu reference count for the blk_mq case is promoted to be used in all block i/o scenarios. This involves initializing it by default, waiting for it to drop to zero at exit, and holding a live reference over the invocation of q->make_request_fn() in generic_make_request(). The blk_mq code continues to take its own reference per blk_mq request and retains the ability to freeze the queue, but the check that the queue is frozen is moved to generic_make_request(). This fixes crash signatures like the following: BUG: unable to handle kernel paging request at ffff880140000000 [..] Call Trace: [] ? copy_user_handle_tail+0x5f/0x70 [] pmem_do_bvec.isra.11+0x70/0xf0 [nd_pmem] [] pmem_make_request+0xd1/0x200 [nd_pmem] [] ? mempool_alloc+0x72/0x1a0 [] generic_make_request+0xd6/0x110 [] submit_bio+0x76/0x170 [] submit_bh_wbc+0x12f/0x160 [] submit_bh+0x12/0x20 [] jbd2_write_superblock+0x8d/0x170 [] jbd2_mark_journal_empty+0x5d/0x90 [] jbd2_journal_destroy+0x24b/0x270 [] ? put_pwq_unlocked+0x2a/0x30 [] ? destroy_workqueue+0x225/0x250 [] ext4_put_super+0x64/0x360 [] generic_shutdown_super+0x6a/0xf0 Cc: Jens Axboe Cc: Keith Busch Cc: Ross Zwisler Suggested-by: Christoph Hellwig Signed-off-by: Dan Williams --- block/blk-core.c | 71 ++++++++++++++++++++++++++++++++++++++------ block/blk-mq-sysfs.c | 6 ---- block/blk-mq.c | 80 +++++++++++++++----------------------------------- block/blk-sysfs.c | 3 +- block/blk.h | 14 +++++++++ include/linux/blk-mq.h | 1 - include/linux/blkdev.h | 2 +- 7 files changed, 102 insertions(+), 75 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 2eb722d48773..6062550baaef 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -554,19 +554,17 @@ void blk_cleanup_queue(struct request_queue *q) * Drain all requests queued before DYING marking. Set DEAD flag to * prevent that q->request_fn() gets invoked after draining finished. */ - if (q->mq_ops) { - blk_mq_freeze_queue(q); - spin_lock_irq(lock); - } else { - spin_lock_irq(lock); + blk_freeze_queue(q); + spin_lock_irq(lock); + if (!q->mq_ops) __blk_drain_queue(q, true); - } queue_flag_set(QUEUE_FLAG_DEAD, q); spin_unlock_irq(lock); /* @q won't process any more request, flush async actions */ del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer); blk_sync_queue(q); + percpu_ref_exit(&q->q_usage_counter); if (q->mq_ops) blk_mq_free_queue(q); @@ -629,6 +627,40 @@ struct request_queue *blk_alloc_queue(gfp_t gfp_mask) } EXPORT_SYMBOL(blk_alloc_queue); +int blk_queue_enter(struct request_queue *q, gfp_t gfp) +{ + while (true) { + int ret; + + if (percpu_ref_tryget_live(&q->q_usage_counter)) + return 0; + + if (!(gfp & __GFP_WAIT)) + return -EBUSY; + + ret = wait_event_interruptible(q->mq_freeze_wq, + !atomic_read(&q->mq_freeze_depth) || + blk_queue_dying(q)); + if (blk_queue_dying(q)) + return -ENODEV; + if (ret) + return ret; + } +} + +void blk_queue_exit(struct request_queue *q) +{ + percpu_ref_put(&q->q_usage_counter); +} + +static void blk_queue_usage_counter_release(struct percpu_ref *ref) +{ + struct request_queue *q = + container_of(ref, struct request_queue, q_usage_counter); + + wake_up_all(&q->mq_freeze_wq); +} + struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) { struct request_queue *q; @@ -690,11 +722,22 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) init_waitqueue_head(&q->mq_freeze_wq); - if (blkcg_init_queue(q)) + /* + * Init percpu_ref in atomic mode so that it's faster to shutdown. + * See blk_register_queue() for details. + */ + if (percpu_ref_init(&q->q_usage_counter, + blk_queue_usage_counter_release, + PERCPU_REF_INIT_ATOMIC, GFP_KERNEL)) goto fail_bdi; + if (blkcg_init_queue(q)) + goto fail_ref; + return q; +fail_ref: + percpu_ref_exit(&q->q_usage_counter); fail_bdi: bdi_destroy(&q->backing_dev_info); fail_split: @@ -1966,9 +2009,19 @@ void generic_make_request(struct bio *bio) do { struct request_queue *q = bdev_get_queue(bio->bi_bdev); - q->make_request_fn(q, bio); + if (likely(blk_queue_enter(q, __GFP_WAIT) == 0)) { + + q->make_request_fn(q, bio); + + blk_queue_exit(q); - bio = bio_list_pop(current->bio_list); + bio = bio_list_pop(current->bio_list); + } else { + struct bio *bio_next = bio_list_pop(current->bio_list); + + bio_io_error(bio); + bio = bio_next; + } } while (bio); current->bio_list = NULL; /* deactivate */ } diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index 279c5d674edf..731b6eecce82 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -412,12 +412,6 @@ static void blk_mq_sysfs_init(struct request_queue *q) kobject_init(&ctx->kobj, &blk_mq_ctx_ktype); } -/* see blk_register_queue() */ -void blk_mq_finish_init(struct request_queue *q) -{ - percpu_ref_switch_to_percpu(&q->mq_usage_counter); -} - int blk_mq_register_disk(struct gendisk *disk) { struct device *dev = disk_to_dev(disk); diff --git a/block/blk-mq.c b/block/blk-mq.c index f2d67b4047a0..6d91894cf85e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -77,47 +77,13 @@ static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx, clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word); } -static int blk_mq_queue_enter(struct request_queue *q, gfp_t gfp) -{ - while (true) { - int ret; - - if (percpu_ref_tryget_live(&q->mq_usage_counter)) - return 0; - - if (!(gfp & __GFP_WAIT)) - return -EBUSY; - - ret = wait_event_interruptible(q->mq_freeze_wq, - !atomic_read(&q->mq_freeze_depth) || - blk_queue_dying(q)); - if (blk_queue_dying(q)) - return -ENODEV; - if (ret) - return ret; - } -} - -static void blk_mq_queue_exit(struct request_queue *q) -{ - percpu_ref_put(&q->mq_usage_counter); -} - -static void blk_mq_usage_counter_release(struct percpu_ref *ref) -{ - struct request_queue *q = - container_of(ref, struct request_queue, mq_usage_counter); - - wake_up_all(&q->mq_freeze_wq); -} - void blk_mq_freeze_queue_start(struct request_queue *q) { int freeze_depth; freeze_depth = atomic_inc_return(&q->mq_freeze_depth); if (freeze_depth == 1) { - percpu_ref_kill(&q->mq_usage_counter); + percpu_ref_kill(&q->q_usage_counter); blk_mq_run_hw_queues(q, false); } } @@ -125,18 +91,34 @@ EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_start); static void blk_mq_freeze_queue_wait(struct request_queue *q) { - wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter)); + wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter)); } /* * Guarantee no request is in use, so we can change any data structure of * the queue afterward. */ -void blk_mq_freeze_queue(struct request_queue *q) +void blk_freeze_queue(struct request_queue *q) { + /* + * In the !blk_mq case we are only calling this to kill the + * q_usage_counter, otherwise this increases the freeze depth + * and waits for it to return to zero. For this reason there is + * no blk_unfreeze_queue(), and blk_freeze_queue() is not + * exported to drivers as the only user for unfreeze is blk_mq. + */ blk_mq_freeze_queue_start(q); blk_mq_freeze_queue_wait(q); } + +void blk_mq_freeze_queue(struct request_queue *q) +{ + /* + * ...just an alias to keep freeze and unfreeze actions balanced + * in the blk_mq_* namespace + */ + blk_freeze_queue(q); +} EXPORT_SYMBOL_GPL(blk_mq_freeze_queue); void blk_mq_unfreeze_queue(struct request_queue *q) @@ -146,7 +128,7 @@ void blk_mq_unfreeze_queue(struct request_queue *q) freeze_depth = atomic_dec_return(&q->mq_freeze_depth); WARN_ON_ONCE(freeze_depth < 0); if (!freeze_depth) { - percpu_ref_reinit(&q->mq_usage_counter); + percpu_ref_reinit(&q->q_usage_counter); wake_up_all(&q->mq_freeze_wq); } } @@ -255,7 +237,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp, struct blk_mq_alloc_data alloc_data; int ret; - ret = blk_mq_queue_enter(q, gfp); + ret = blk_queue_enter(q, gfp); if (ret) return ERR_PTR(ret); @@ -278,7 +260,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp, } blk_mq_put_ctx(ctx); if (!rq) { - blk_mq_queue_exit(q); + blk_queue_exit(q); return ERR_PTR(-EWOULDBLOCK); } return rq; @@ -297,7 +279,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx, clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags); blk_mq_put_tag(hctx, tag, &ctx->last_tag); - blk_mq_queue_exit(q); + blk_queue_exit(q); } void blk_mq_free_hctx_request(struct blk_mq_hw_ctx *hctx, struct request *rq) @@ -1184,11 +1166,7 @@ static struct request *blk_mq_map_request(struct request_queue *q, int rw = bio_data_dir(bio); struct blk_mq_alloc_data alloc_data; - if (unlikely(blk_mq_queue_enter(q, GFP_KERNEL))) { - bio_io_error(bio); - return NULL; - } - + blk_queue_enter_live(q); ctx = blk_mq_get_ctx(q); hctx = q->mq_ops->map_queue(q, ctx->cpu); @@ -1979,14 +1957,6 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, hctxs[i]->queue_num = i; } - /* - * Init percpu_ref in atomic mode so that it's faster to shutdown. - * See blk_register_queue() for details. - */ - if (percpu_ref_init(&q->mq_usage_counter, blk_mq_usage_counter_release, - PERCPU_REF_INIT_ATOMIC, GFP_KERNEL)) - goto err_hctxs; - setup_timer(&q->timeout, blk_mq_rq_timer, (unsigned long) q); blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ); @@ -2062,8 +2032,6 @@ void blk_mq_free_queue(struct request_queue *q) blk_mq_exit_hw_queues(q, set, set->nr_hw_queues); blk_mq_free_hw_queues(q, set); - percpu_ref_exit(&q->mq_usage_counter); - kfree(q->mq_map); q->mq_map = NULL; diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 3e44a9da2a13..61fc2633bbea 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -599,9 +599,8 @@ int blk_register_queue(struct gendisk *disk) */ if (!blk_queue_init_done(q)) { queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q); + percpu_ref_switch_to_percpu(&q->q_usage_counter); blk_queue_bypass_end(q); - if (q->mq_ops) - blk_mq_finish_init(q); } ret = blk_trace_init_sysfs(dev); diff --git a/block/blk.h b/block/blk.h index 98614ad37c81..5b2cd393afbe 100644 --- a/block/blk.h +++ b/block/blk.h @@ -72,6 +72,20 @@ void blk_dequeue_request(struct request *rq); void __blk_queue_free_tags(struct request_queue *q); bool __blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes, unsigned int bidi_bytes); +int blk_queue_enter(struct request_queue *q, gfp_t gfp); +void blk_queue_exit(struct request_queue *q); +void blk_freeze_queue(struct request_queue *q); + +static inline void blk_queue_enter_live(struct request_queue *q) +{ + /* + * Given that running in generic_make_request() context + * guarantees that a live reference against q_usage_counter has + * been established, further references under that same context + * need not check that the queue has been frozen (marked dead). + */ + percpu_ref_get(&q->q_usage_counter); +} void blk_rq_timed_out_timer(unsigned long data); unsigned long blk_rq_timeout(unsigned long timeout); diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 37d1602c4f7a..25ce763fbb81 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -167,7 +167,6 @@ enum { struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *); struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, struct request_queue *q); -void blk_mq_finish_init(struct request_queue *q); int blk_mq_register_disk(struct gendisk *); void blk_mq_unregister_disk(struct gendisk *); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 99da9ebc7377..0a0def66c61e 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -450,7 +450,7 @@ struct request_queue { #endif struct rcu_head rcu_head; wait_queue_head_t mq_freeze_wq; - struct percpu_ref mq_usage_counter; + struct percpu_ref q_usage_counter; struct list_head all_q_node; struct blk_mq_tag_set *tag_set; -- 2.1.0 {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I