From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 36DF08F55 for ; Sun, 16 Jul 2023 20:31:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB2DAC433C9; Sun, 16 Jul 2023 20:31:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689539476; bh=8uLWVgUzKUcTbGBBUWSFtguRGiA/2oFlGn4riYrsJpc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SPTRZSbW5ZKCf1X6P9FnmbYkERHQ8luztcnOfo+xe8uP3st2YnDVCY/bajpsak8zV RRrxqgLPqajnEelHpYH/fBHxxN4tKprZ+Wqdy2Q3lPrFGWsy0jOPr1CoDuz3IhyiDw iQCjl06TVc3gyiLqJVVDa+kUw1JzPr5ABGJa8ENk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yu Kuai , Jan Kara , Jens Axboe , Sasha Levin Subject: [PATCH 6.1 013/591] blk-mq: fix potential io hang by wrong wake_batch Date: Sun, 16 Jul 2023 21:42:32 +0200 Message-ID: <20230716194924.206867704@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230716194923.861634455@linuxfoundation.org> References: <20230716194923.861634455@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Yu Kuai [ Upstream commit 4f1731df60f9033669f024d06ae26a6301260b55 ] 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 Link: https://lore.kernel.org/r/20230610023043.2559121-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- 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 bd942341b6382..7675e663df365 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -427,7 +427,7 @@ 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 a80d7c62bdfe6..100889c276c3f 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -40,6 +40,7 @@ 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, @@ -57,9 +58,11 @@ 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); } /* @@ -92,9 +95,11 @@ 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 0b2870839cdd6..c6eca452ea2a2 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -362,8 +362,7 @@ 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 a9764cbf7f8d2..e4f676e1042b5 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -745,8 +745,7 @@ 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; -- 2.39.2