From patchwork Wed Apr 15 13:00:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Giuliano Procida X-Patchwork-Id: 227955 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=-17.4 required=3.0 tests=DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 110D8C2BA19 for ; Wed, 15 Apr 2020 13:00:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD3E42078B for ; Wed, 15 Apr 2020 13:00:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Kh9PxRKS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2505701AbgDONAj (ORCPT ); Wed, 15 Apr 2020 09:00:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2505704AbgDONAf (ORCPT ); Wed, 15 Apr 2020 09:00:35 -0400 Received: from mail-wr1-x449.google.com (mail-wr1-x449.google.com [IPv6:2a00:1450:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A07DC061A0C for ; Wed, 15 Apr 2020 06:00:35 -0700 (PDT) Received: by mail-wr1-x449.google.com with SMTP id q10so3990178wrv.10 for ; Wed, 15 Apr 2020 06:00:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=2UV+AKDA4iEmqm7ZUjmQLtTc9rj0RmktA+MuCIQAXQs=; b=Kh9PxRKS3VUM33vtK19o53nAO6ex33O7LCJaEhBiAg9o9KPZIkZ9ajIGr+dl4iiBkY 0JaVhxnVbtGWikryxmfbfnM7O2NASXKbmixSu7a6sNRozwlbWs12+mshAvCycnd8bXle hfVNEPPYA64rT0RuZww0GdpYspaWCGm7E07MicehKsTJU1QAxCHHzfImJKJHIEjJNGYa f+u5kiB0KbNTNnWKhB1HEgGypfPJ4L9l3EkG1oE6H9fZrfRWO5ARfLZS+FbX1TClF6FR 5vbWaoyIm8exxKPlvRIvB+IQgMt1Lh0VhW95UDwYMJ2s5r72NeWQh8jO6ESwSejZnYNN gHpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=2UV+AKDA4iEmqm7ZUjmQLtTc9rj0RmktA+MuCIQAXQs=; b=UzKl1v9Ubb55p3hwG1dDtkDWUETxg8CME4OT3w7neDMLktUJaavufjufkROeShxmUE kJBiEAnZqUxiNDRbmVyHsd4ctUi/H1EFPH4SxjXssUUF4JkXbeWJRtmO2JuZCzTNyfov /GJ/RwN5TuARLTo/WnetA74KtNBkTk1uJIU1FoXQhZwBkTHJST0TsYTnOBhHs3cGaz2F 7M04E8OPWaMARnEBgkbGnhTsBEvADfZq8NT76Fxje7HEmBFU1dySapOXXqbvwG1TpRjB wi4dQZtFgAIpILtURqtx9xJaOZ/QnQED5qx6zpbmSQzqWHUHW/d+nPY6J9KQrru44uSi BHTA== X-Gm-Message-State: AGi0PuZ37oF1vb2Iu6bhUv7DvoBziZltzFBi+D7WPWly6P6PVaSKZFRl WAZIzI3OO+9LUe/kjuR1rRqOUrSuDXmwRA== X-Google-Smtp-Source: APiQypL9uylGrQea/UxwB1BDWUUiyk0xf/DrSmA5OjRIN8UrN+0JmEn8GdhYHxzHW/zEZTZIcU2NaPyRs7YYFg== X-Received: by 2002:adf:dd83:: with SMTP id x3mr21196481wrl.298.1586955634125; Wed, 15 Apr 2020 06:00:34 -0700 (PDT) Date: Wed, 15 Apr 2020 14:00:17 +0100 In-Reply-To: Message-Id: <20200415130017.244979-5-gprocida@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.26.0.110.g2183baf09c-goog Subject: [PATCH v2 4/4] blk-mq: Allow blocking queue tag iter callbacks From: Giuliano Procida To: greg@kroah.com Cc: Giuliano Procida , stable@vger.kernel.org, Jianchao Wang , Keith Busch , Jens Axboe Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org commit 530ca2c9bd6949c72c9b5cfc330cb3dbccaa3f5b upstream. A recent commit runs tag iterator callbacks under the rcu read lock, but existing callbacks do not satisfy the non-blocking requirement. The commit intended to prevent an iterator from accessing a queue that's being modified. This patch fixes the original issue by taking a queue reference instead of reading it, which allows callbacks to make blocking calls. Fixes: f5bbbbe4d6357 ("blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter") Acked-by: Jianchao Wang Signed-off-by: Keith Busch Signed-off-by: Jens Axboe Signed-off-by: Giuliano Procida --- block/blk-mq-tag.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index bf356de30134..c1c654319287 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -484,11 +484,8 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, /* * Avoid potential races with things like queue removal. */ - rcu_read_lock(); - if (percpu_ref_is_zero(&q->q_usage_counter)) { - rcu_read_unlock(); + if (!percpu_ref_tryget(&q->q_usage_counter)) return; - } queue_for_each_hw_ctx(q, hctx, i) { struct blk_mq_tags *tags = hctx->tags; @@ -505,7 +502,7 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, bt_for_each(hctx, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv, false); } - rcu_read_unlock(); + blk_queue_exit(q); } static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt)