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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 B49BAC433ED for ; Wed, 5 May 2021 15:00:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90125613BA for ; Wed, 5 May 2021 15:00:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232327AbhEEPB3 (ORCPT ); Wed, 5 May 2021 11:01:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:54475 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232314AbhEEPB3 (ORCPT ); Wed, 5 May 2021 11:01:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620226832; h=from:from:reply-to:subject:subject: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=FnKGMrpRyV8NQ9pDisyD52tnueLAa5EI5Tw8ZvCTQ6Q=; b=ZChQQqjRdNyeyzO1TTzeA6c4VkkCMEqgB/X7IrtQ7brZwwu5HZ2W+CZnxvZa+B//SuS3TH 1SSY4IrHKQJhqZs2uTBnupZlwWv1RnfufkDZpfMJ5xIf9eMQv23DhdyGh7sZvolHJyjz4l jUKX7fEW6f7YXPUWy/QdCpkqN2ukb/o= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-218-MEkHIQ0EOcm6Wc2ApmUNHQ-1; Wed, 05 May 2021 11:00:30 -0400 X-MC-Unique: MEkHIQ0EOcm6Wc2ApmUNHQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 78D051923781; Wed, 5 May 2021 15:00:29 +0000 (UTC) Received: from localhost (ovpn-12-80.pek2.redhat.com [10.72.12.80]) by smtp.corp.redhat.com (Postfix) with ESMTP id 47D4D687C9; Wed, 5 May 2021 15:00:05 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Bart Van Assche , Hannes Reinecke , John Garry , David Jeffery , Ming Lei Subject: [PATCH V5 3/4] blk-mq: clear stale request in tags->rq[] before freeing one request pool Date: Wed, 5 May 2021 22:58:54 +0800 Message-Id: <20210505145855.174127-4-ming.lei@redhat.com> In-Reply-To: <20210505145855.174127-1-ming.lei@redhat.com> References: <20210505145855.174127-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org refcount_inc_not_zero() in bt_tags_iter() still may read one freed request. Fix the issue by the following approach: 1) hold a per-tags spinlock when reading ->rqs[tag] and calling refcount_inc_not_zero in bt_tags_iter() 2) clearing stale request referred via ->rqs[tag] before freeing request pool, the per-tags spinlock is held for clearing stale ->rq[tag] So after we cleared stale requests, bt_tags_iter() won't observe freed request any more, also the clearing will wait for pending request reference. The idea of clearing ->rqs[] is borrowed from John Garry's previous patch and one recent David's patch. Tested-by: John Garry Reviewed-by: David Jeffery Reviewed-by: Bart Van Assche Signed-off-by: Ming Lei --- block/blk-mq-tag.c | 8 +++++++- block/blk-mq-tag.h | 3 +++ block/blk-mq.c | 39 ++++++++++++++++++++++++++++++++++----- 3 files changed, 44 insertions(+), 6 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 4a40d409f5dd..8b239dcce85f 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -203,9 +203,14 @@ static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags, unsigned int bitnr) { struct request *rq = tags->rqs[bitnr]; + unsigned long flags; - if (!rq || !refcount_inc_not_zero(&rq->ref)) + spin_lock_irqsave(&tags->lock, flags); + if (!rq || !refcount_inc_not_zero(&rq->ref)) { + spin_unlock_irqrestore(&tags->lock, flags); return NULL; + } + spin_unlock_irqrestore(&tags->lock, flags); return rq; } @@ -538,6 +543,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, tags->nr_tags = total_tags; tags->nr_reserved_tags = reserved_tags; + spin_lock_init(&tags->lock); if (blk_mq_is_sbitmap_shared(flags)) return tags; diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index 7d3e6b333a4a..f942a601b5ef 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -20,6 +20,9 @@ struct blk_mq_tags { struct request **rqs; struct request **static_rqs; struct list_head page_list; + + /* used to clear rqs[] before one request pool is freed */ + spinlock_t lock; }; extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, diff --git a/block/blk-mq.c b/block/blk-mq.c index d053e80fa6d7..c1b28e09a27e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2306,6 +2306,38 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio) return BLK_QC_T_NONE; } +static size_t order_to_size(unsigned int order) +{ + return (size_t)PAGE_SIZE << order; +} + +/* called before freeing request pool in @tags */ +static void blk_mq_clear_rq_mapping(struct blk_mq_tag_set *set, + struct blk_mq_tags *tags, unsigned int hctx_idx) +{ + struct blk_mq_tags *drv_tags = set->tags[hctx_idx]; + struct page *page; + unsigned long flags; + + spin_lock_irqsave(&drv_tags->lock, flags); + list_for_each_entry(page, &tags->page_list, lru) { + unsigned long start = (unsigned long)page_address(page); + unsigned long end = start + order_to_size(page->private); + int i; + + for (i = 0; i < set->queue_depth; i++) { + struct request *rq = drv_tags->rqs[i]; + unsigned long rq_addr = (unsigned long)rq; + + if (rq_addr >= start && rq_addr < end) { + WARN_ON_ONCE(refcount_read(&rq->ref) != 0); + cmpxchg(&drv_tags->rqs[i], rq, NULL); + } + } + } + spin_unlock_irqrestore(&drv_tags->lock, flags); +} + void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags, unsigned int hctx_idx) { @@ -2324,6 +2356,8 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags, } } + blk_mq_clear_rq_mapping(set, tags, hctx_idx); + while (!list_empty(&tags->page_list)) { page = list_first_entry(&tags->page_list, struct page, lru); list_del_init(&page->lru); @@ -2383,11 +2417,6 @@ struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, return tags; } -static size_t order_to_size(unsigned int order) -{ - return (size_t)PAGE_SIZE << order; -} - static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq, unsigned int hctx_idx, int node) { -- 2.29.2