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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6FB73C3DA4A for ; Tue, 20 Aug 2024 22:39:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7D5B66B0085; Tue, 20 Aug 2024 18:39:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 75E656B0088; Tue, 20 Aug 2024 18:39:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5FE076B0089; Tue, 20 Aug 2024 18:39:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 3F2BE6B0085 for ; Tue, 20 Aug 2024 18:39:06 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id B0CE41A05C1 for ; Tue, 20 Aug 2024 22:39:05 +0000 (UTC) X-FDA: 82474090650.07.69E4DE5 Received: from mail78-59.sinamail.sina.com.cn (mail78-59.sinamail.sina.com.cn [219.142.78.59]) by imf09.hostedemail.com (Postfix) with ESMTP id 1F6AD14001B for ; Tue, 20 Aug 2024 22:39:01 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf09.hostedemail.com: domain of hdanton@sina.com designates 219.142.78.59 as permitted sender) smtp.mailfrom=hdanton@sina.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724193528; a=rsa-sha256; cv=none; b=HXK0xvZoOuP/3KpTnQYwqmdbZr9RjvttSJyI5ETSvGYxQCDglod6F0zyt16lkU8TqfQJAG 03ghNl6xHpaOhp9Gdx260YzlBVFM6Pch0V5u+/EUCzhPtI/nNyAtlZ03HQINaYa5X9+wEW aH4ulb3s6gYpJuzJ1NCwjq9iidA1qtg= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf09.hostedemail.com: domain of hdanton@sina.com designates 219.142.78.59 as permitted sender) smtp.mailfrom=hdanton@sina.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724193528; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references; bh=on7roJKRMMlEs9Io03F9gG7vVpjhL65HOapRQNKRuKE=; b=Uos8iMZa4l1SqdPnXPOTLHefq0gtcA8PZ6CGcGvTO5iZxWBpkT0IKxtQ1jSE38Lgyj7Zk1 +3H3aWsxO9fuJZB6ZhhTOmniZx59G/I/YGWlv5RwYesIH26jfcgB55j2Nx2CCyBgxp6+qC oGjGJii9PCkyxUynFpV73MHPDRDkn+E= X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([113.118.66.189]) by sina.com (10.185.250.24) with ESMTP id 66C51AFE00005C77; Tue, 21 Aug 2024 06:38:57 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com X-SMAIL-MID: 23513810748479 X-SMAIL-UIID: A5E29B964BFE4EC482B6F72378661E3A-20240821-063857-1 From: Hillf Danton To: "Liam R. Howlett" Cc: Andrew Morton , maple-tree@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Paul E. McKenney" , "Liam R. Howlett" , syzbot+036af2f0c7338a33b0cd@syzkaller.appspotmail.com Subject: Re: [PATCH] maple_tree: Remove rcu_read_lock() from mt_validate() Date: Wed, 21 Aug 2024 06:38:45 +0800 Message-ID: <20240820175417.2782532-1-Liam.Howlett@oracle.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 1F6AD14001B X-Rspamd-Server: rspam01 X-Stat-Signature: rysse6p18ei8h64kqw44rntzxpd9pr1f X-HE-Tag: 1724193541-818241 X-HE-Meta: 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 8IeomH2f 0E3Ca6VRZLwOSKGGx2FHam+KBA4me6IKr4YHg+uB84Cot9MxgWbBxoQQAZ4wJ0GC2BcZlyxA82i/VqzVlOjnLfiL9YoBpbwfCAYdKIjyQ/tYKSPa2Qc1dChHCXJ03I4hAMb+IJkN2Oqv8mitdILcX8aIGx9ZFQ95ZFD67pYz3uKCtf3R0FYMY7vgeVrjYfC/n3lq2qQpRgNrxeZDulWT9jE0jF7rzWBSW4nzuCQZnW+A308weyQ9iuiVXinpCqvQb+/nL6/VXAGLS79bFCbDAZBPHTPaMkJrOWw/UJglDAuXpd8LOpqldwiVMEjA+O7XcmWFs6kxr+6u4KMmhGnf+NQRGkmYgyWjRCBYK9Xvr9IlMY+c4QMlEjvb9Lgd6T4cJTIHbIBZlqR2Q6dIHvx53EZ4FGwsjNzbU/Rm86ZgPBTAJuRbeQouGkr6vqONgbAH+dvSi X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Message-ID: <20240820223845.pfNZ8kTk3qagu7kMVy4sJ8_nUCP26ftd3w4BSSQDgHc@z> On Tue, 20 Aug 2024 13:54:17 -0400 "Liam R. Howlett" > > The write lock should be held when validating the tree to avoid updates > racing with checks. Holding the rcu read lock during a large tree > validation may also cause a prolonged rcu read window. > >From the rcu stall's view, holding spin lock plays the same role of rcu read lock, so what are you fixing by simply dropping rcu read lock? > Link: https://lore.kernel.org/all/0000000000001d12d4062005aea1@google.com/ > Fixes: 54a611b60590 ("Maple Tree: add new data structure") > Signed-off-by: Liam R. Howlett > Reported-by: syzbot+036af2f0c7338a33b0cd@syzkaller.appspotmail.com > --- > lib/maple_tree.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/lib/maple_tree.c b/lib/maple_tree.c > index 755ba8b18e14..fe1b01b29201 100644 > --- a/lib/maple_tree.c > +++ b/lib/maple_tree.c > @@ -7588,14 +7588,14 @@ static void mt_validate_nulls(struct maple_tree *mt) > * 2. The gap is correctly set in the parents > */ > void mt_validate(struct maple_tree *mt) > + __must_hold(mas->tree->ma_lock) > { > unsigned char end; > lockdep_assert_held(ma_lock); instead > MA_STATE(mas, mt, 0, 0); > - rcu_read_lock(); > mas_start(&mas); > if (!mas_is_active(&mas)) > - goto done; > + return; > > while (!mte_is_leaf(mas.node)) > mas_descend(&mas); > @@ -7616,9 +7616,6 @@ void mt_validate(struct maple_tree *mt) > mas_dfs_postorder(&mas, ULONG_MAX); > } > mt_validate_nulls(mt); > -done: > - rcu_read_unlock(); > - > } > EXPORT_SYMBOL_GPL(mt_validate); > > -- > 2.43.0