From patchwork Sat Jun 10 02:30:43 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 13274703 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1C59C7EE2E for ; Sat, 10 Jun 2023 02:35:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232413AbjFJCfI (ORCPT ); Fri, 9 Jun 2023 22:35:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49338 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229942AbjFJCfG (ORCPT ); Fri, 9 Jun 2023 22:35:06 -0400 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5628935B3; Fri, 9 Jun 2023 19:35:04 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4QdMVX4xj3z4f3m7K; Sat, 10 Jun 2023 10:35:00 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP4 (Coremail) with SMTP id gCh0CgAHoZRT4YNktllkLQ--.11524S4; Sat, 10 Jun 2023 10:35:01 +0800 (CST) From: Yu Kuai To: jack@suse.cz, axboe@kernel.dk, qiulaibin@huawei.com, andriy.shevchenko@linux.intel.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com Subject: [PATCH -next v2] blk-mq: fix potential io hang by wrong 'wake_batch' Date: Sat, 10 Jun 2023 10:30:43 +0800 Message-Id: <20230610023043.2559121-1-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-CM-TRANSID: gCh0CgAHoZRT4YNktllkLQ--.11524S4 X-Coremail-Antispam: 1UD129KBjvJXoWxXrWrAFW7Jr15ZrWfWw4kJFb_yoWrJF4fpa yUCa17Kw1Sqr1UXayDt39rXF1Sgan0yr13Jrsaqa4YvF1j9r1fXr18urW0qrW0qrs3AF43 urs8trW8tF4UG37anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvY14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26ryj6F1UM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E 2Ix0cI8IcVAFwI0_JrI_JrylYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJV W8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1lFIxGxcIEc7CjxVA2 Y2ka0xkIwI1l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4 xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43 MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_JFI_Gr1lIxAIcVC0I7IYx2IY6xkF7I 0E14v26F4j6r4UJwCI42IY6xAIw20EY4v20xvaj40_Zr0_Wr1UMIIF0xvEx4A2jsIE14v2 6r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0J UZa9-UUUUU= X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Yu Kuai In __blk_mq_tag_busy/idle(), updating 'active_queues' and calculating 'wake_batch' is not atomic: t1: t2: _blk_mq_tag_busy blk_mq_tag_busy inc active_queues // assume 1->2 inc active_queues // 2 -> 3 blk_mq_update_wake_batch // calculate based on 3 blk_mq_update_wake_batch /* calculate based on 2, while active_queues is actually 3. */ Fix this problem by protecting them wih 'tags->lock', this is not a hot path, so performance should not be concerned. And now that all writers are inside the lock, switch 'actives_queues' from atomic to unsigned int. Fixes: 180dccb0dba4 ("blk-mq: fix tag_get wait task can't be awakened") Signed-off-by: Yu Kuai Reviewed-by: Jan Kara --- Changes in v2: - switch 'active_queues' from atomic to unsigned int. block/blk-mq-debugfs.c | 2 +- block/blk-mq-tag.c | 15 ++++++++++----- block/blk-mq.h | 3 +-- include/linux/blk-mq.h | 3 +-- 4 files changed, 13 insertions(+), 10 deletions(-) diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index 68165a50951b..c3b5930106b2 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -401,7 +401,7 @@ static void blk_mq_debugfs_tags_show(struct seq_file *m, seq_printf(m, "nr_tags=%u\n", tags->nr_tags); seq_printf(m, "nr_reserved_tags=%u\n", tags->nr_reserved_tags); seq_printf(m, "active_queues=%d\n", - atomic_read(&tags->active_queues)); + READ_ONCE(tags->active_queues)); seq_puts(m, "\nbitmap_tags:\n"); sbitmap_queue_show(&tags->bitmap_tags, m); diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index dfd81cab5788..cc57e2dd9a0b 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -38,6 +38,7 @@ static void blk_mq_update_wake_batch(struct blk_mq_tags *tags, void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx) { unsigned int users; + struct blk_mq_tags *tags = hctx->tags; /* * calling test_bit() prior to test_and_set_bit() is intentional, @@ -55,9 +56,11 @@ void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx) return; } - users = atomic_inc_return(&hctx->tags->active_queues); - - blk_mq_update_wake_batch(hctx->tags, users); + spin_lock_irq(&tags->lock); + users = tags->active_queues + 1; + WRITE_ONCE(tags->active_queues, users); + blk_mq_update_wake_batch(tags, users); + spin_unlock_irq(&tags->lock); } /* @@ -90,9 +93,11 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx) return; } - users = atomic_dec_return(&tags->active_queues); - + spin_lock_irq(&tags->lock); + users = tags->active_queues - 1; + WRITE_ONCE(tags->active_queues, users); blk_mq_update_wake_batch(tags, users); + spin_unlock_irq(&tags->lock); blk_mq_tag_wakeup_all(tags, false); } diff --git a/block/blk-mq.h b/block/blk-mq.h index 8c642e9f32f1..1743857e0b01 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -412,8 +412,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, return true; } - users = atomic_read(&hctx->tags->active_queues); - + users = READ_ONCE(hctx->tags->active_queues); if (!users) return true; diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 59b52ec155b1..f401067ac03a 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -739,8 +739,7 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, struct blk_mq_tags { unsigned int nr_tags; unsigned int nr_reserved_tags; - - atomic_t active_queues; + unsigned int active_queues; struct sbitmap_queue bitmap_tags; struct sbitmap_queue breserved_tags;