From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7FAAEC49EA4 for ; Wed, 23 Jun 2021 09:36:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6B36E6113B for ; Wed, 23 Jun 2021 09:36:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230001AbhFWJi7 (ORCPT ); Wed, 23 Jun 2021 05:38:59 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:60588 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230063AbhFWJi6 (ORCPT ); Wed, 23 Jun 2021 05:38:58 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id EDD7821976; Wed, 23 Jun 2021 09:36:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1624441000; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qB6WZciel8xDXNiwzVgwxTmPDuDpG5WLmuhtMkXt06M=; b=foJa93b4hWL2WpHcjtmksVe/3HTkmqn2PKnE6gAA3BQD3n8IvjF3GZG4d9IFWoTQnCbQvS N7oZk0f0dOni3/SnZ4kTxx4cpI6hAuQhogk7cROEmQJtbIZNdw9DOXeC/nZEm+UsKFlHmZ 4VDre6KBTyyxHIrqR4OoXFMlUpKTT3k= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1624441000; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qB6WZciel8xDXNiwzVgwxTmPDuDpG5WLmuhtMkXt06M=; b=ndt40tXPoFkIO0grQdgo8XwNK/KAZaR2YZuuo4S7G2JFgP51jYRnNi9eFOE835zksVdztq VLmFmO0FbYBk6DBQ== Received: from quack2.suse.cz (unknown [10.100.224.230]) by relay2.suse.de (Postfix) with ESMTP id 8E53FA3B8D; Wed, 23 Jun 2021 09:36:40 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id D11301F2CB0; Wed, 23 Jun 2021 11:36:38 +0200 (CEST) From: Jan Kara To: Jens Axboe Cc: , Paolo Valente , Jan Kara , Ming Lei Subject: [PATCH 2/2] blk: Fix lock inversion between ioc lock and bfqd lock Date: Wed, 23 Jun 2021 11:36:34 +0200 Message-Id: <20210623093634.27879-3-jack@suse.cz> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210623093634.27879-1-jack@suse.cz> References: <20210623093634.27879-1-jack@suse.cz> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=9349; h=from:subject; bh=I7PtGt7lGdlmr6gItnpXl70OEl0U2/tGO8fFojyBRA8=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBg0wCha8qmbTSrQdtEVVpCzKQaGkUrX/tmRRNSkOzR /KhjPluJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCYNMAoQAKCRCcnaoHP2RA2TuqB/ 9Z7Diygb4W/gnn4PifvSEk2IHzBiFkyWfIOyJrheR+teDbEB/x5TCkl49BdswbjwmfS20IuM1hVTz5 nwv9p5CQMxhkPUNR5ixnI5KXbWE/kkjgDKWpUroBv1hVxvIKpewyjZI/SeEbFo61T4wsczBZmpMm4l WbgzXRhGux6VHAQ9vEuKKe9M5w8OI9q0/2/NYaZCjhX2+XxtfewgSmQU09VqKx6Ffc7NSl+jSUAt3D oA0ozeqtASKRcBdKWwl6uJXy+g1vSKg6FyBx6LWHslsJxv5HIdRZPb9NLv09J4WsapIQ0cXNIB5LSH 3Lx5SW4put6i95NqYlx/BUfWjDSZA7 X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Lockdep complains about lock inversion between ioc->lock and bfqd->lock: bfqd -> ioc: put_io_context+0x33/0x90 -> ioc->lock grabbed blk_mq_free_request+0x51/0x140 blk_put_request+0xe/0x10 blk_attempt_req_merge+0x1d/0x30 elv_attempt_insert_merge+0x56/0xa0 blk_mq_sched_try_insert_merge+0x4b/0x60 bfq_insert_requests+0x9e/0x18c0 -> bfqd->lock grabbed blk_mq_sched_insert_requests+0xd6/0x2b0 blk_mq_flush_plug_list+0x154/0x280 blk_finish_plug+0x40/0x60 ext4_writepages+0x696/0x1320 do_writepages+0x1c/0x80 __filemap_fdatawrite_range+0xd7/0x120 sync_file_range+0xac/0xf0 ioc->bfqd: bfq_exit_icq+0xa3/0xe0 -> bfqd->lock grabbed put_io_context_active+0x78/0xb0 -> ioc->lock grabbed exit_io_context+0x48/0x50 do_exit+0x7e9/0xdd0 do_group_exit+0x54/0xc0 To avoid this inversion we change blk_mq_sched_try_insert_merge() to not free the merged request but rather leave that upto the caller similarly to blk_mq_sched_try_merge(). And in bfq_insert_requests() we make sure to free all the merged requests after dropping bfqd->lock. Fixes: aee69d78dec0 ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler") Reviewed-by: Ming Lei Acked-by: Paolo Valente Signed-off-by: Jan Kara --- block/bfq-iosched.c | 6 ++++-- block/blk-merge.c | 19 ++++++++----------- block/blk-mq-sched.c | 5 +++-- block/blk-mq-sched.h | 3 ++- block/blk-mq.h | 11 +++++++++++ block/blk.h | 2 +- block/elevator.c | 11 ++++++++--- block/mq-deadline-main.c | 5 ++++- include/linux/elevator.h | 3 ++- 9 files changed, 43 insertions(+), 22 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 9433d38e486c..727955918563 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2345,9 +2345,9 @@ static bool bfq_bio_merge(struct request_queue *q, struct bio *bio, ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free); + spin_unlock_irq(&bfqd->lock); if (free) blk_mq_free_request(free); - spin_unlock_irq(&bfqd->lock); return ret; } @@ -5969,14 +5969,16 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, struct bfq_queue *bfqq; bool idle_timer_disabled = false; unsigned int cmd_flags; + LIST_HEAD(free); #ifdef CONFIG_BFQ_GROUP_IOSCHED if (!cgroup_subsys_on_dfl(io_cgrp_subsys) && rq->bio) bfqg_stats_update_legacy_io(q, rq); #endif spin_lock_irq(&bfqd->lock); - if (blk_mq_sched_try_insert_merge(q, rq)) { + if (blk_mq_sched_try_insert_merge(q, rq, &free)) { spin_unlock_irq(&bfqd->lock); + blk_mq_free_requests(&free); return; } diff --git a/block/blk-merge.c b/block/blk-merge.c index 4d97fb6dd226..1398b52a24b4 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -846,18 +846,15 @@ static struct request *attempt_front_merge(struct request_queue *q, return NULL; } -int blk_attempt_req_merge(struct request_queue *q, struct request *rq, - struct request *next) +/* + * Try to merge 'next' into 'rq'. Return true if the merge happened, false + * otherwise. The caller is responsible for freeing 'next' if the merge + * happened. + */ +bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, + struct request *next) { - struct request *free; - - free = attempt_merge(q, rq, next); - if (free) { - blk_put_request(free); - return 1; - } - - return 0; + return attempt_merge(q, rq, next); } bool blk_rq_merge_ok(struct request *rq, struct bio *bio) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 2403a5c2b053..c838d81ac058 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -399,9 +399,10 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio, return ret; } -bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq) +bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq, + struct list_head *free) { - return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq); + return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq, free); } EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge); diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h index aff037cfd8e7..5246ae040704 100644 --- a/block/blk-mq-sched.h +++ b/block/blk-mq-sched.h @@ -13,7 +13,8 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs, struct request **merged_request); bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs); -bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq); +bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq, + struct list_head *free); void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx); void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx); diff --git a/block/blk-mq.h b/block/blk-mq.h index 4b1ca7b7bbeb..d08779f77a26 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -302,6 +302,17 @@ static inline struct blk_plug *blk_mq_plug(struct request_queue *q, return NULL; } +/* Free all requests on the list */ +static inline void blk_mq_free_requests(struct list_head *list) +{ + while (!list_empty(list)) { + struct request *rq = list_entry_rq(list->next); + + list_del_init(&rq->queuelist); + blk_mq_free_request(rq); + } +} + /* * For shared tag users, we track the number of currently active users * and attempt to provide a fair share of the tag depth for each of them. diff --git a/block/blk.h b/block/blk.h index d3fa47af3607..9ad3c7ee6ba0 100644 --- a/block/blk.h +++ b/block/blk.h @@ -224,7 +224,7 @@ ssize_t part_timeout_store(struct device *, struct device_attribute *, void __blk_queue_split(struct bio **bio, unsigned int *nr_segs); int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs); -int blk_attempt_req_merge(struct request_queue *q, struct request *rq, +bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, struct request *next); unsigned int blk_recalc_rq_segments(struct request *rq); void blk_rq_set_mixed_merge(struct request *rq); diff --git a/block/elevator.c b/block/elevator.c index 85d0d4adbb64..52ada14cfe45 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -350,9 +350,11 @@ enum elv_merge elv_merge(struct request_queue *q, struct request **req, * we can append 'rq' to an existing request, so we can throw 'rq' away * afterwards. * - * Returns true if we merged, false otherwise + * Returns true if we merged, false otherwise. 'free' will contain all + * requests that need to be freed. */ -bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) +bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq, + struct list_head *free) { struct request *__rq; bool ret; @@ -363,8 +365,10 @@ bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) /* * First try one-hit cache. */ - if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) + if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) { + list_add(&rq->queuelist, free); return true; + } if (blk_queue_noxmerges(q)) return false; @@ -378,6 +382,7 @@ bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) if (!__rq || !blk_attempt_req_merge(q, __rq, rq)) break; + list_add(&rq->queuelist, free); /* The merged request could be merged with others, try again */ ret = true; rq = __rq; diff --git a/block/mq-deadline-main.c b/block/mq-deadline-main.c index 4815e536091f..9db6da9ef4c6 100644 --- a/block/mq-deadline-main.c +++ b/block/mq-deadline-main.c @@ -719,6 +719,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, struct dd_per_prio *per_prio; enum dd_prio prio; struct dd_blkcg *blkcg; + LIST_HEAD(free); lockdep_assert_held(&dd->lock); @@ -742,8 +743,10 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, WARN_ON_ONCE(rq->elv.priv[0]); rq->elv.priv[0] = blkcg; - if (blk_mq_sched_try_insert_merge(q, rq)) + if (blk_mq_sched_try_insert_merge(q, rq, &free)) { + blk_mq_free_requests(&free); return; + } trace_block_rq_insert(rq); diff --git a/include/linux/elevator.h b/include/linux/elevator.h index 783ecb3cb77a..ef9ceead3db1 100644 --- a/include/linux/elevator.h +++ b/include/linux/elevator.h @@ -117,7 +117,8 @@ extern void elv_merge_requests(struct request_queue *, struct request *, struct request *); extern void elv_merged_request(struct request_queue *, struct request *, enum elv_merge); -extern bool elv_attempt_insert_merge(struct request_queue *, struct request *); +extern bool elv_attempt_insert_merge(struct request_queue *, struct request *, + struct list_head *); extern struct request *elv_former_request(struct request_queue *, struct request *); extern struct request *elv_latter_request(struct request_queue *, struct request *); void elevator_init_mq(struct request_queue *q); -- 2.26.2