From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp153-171.sina.com.cn (smtp153-171.sina.com.cn [61.135.153.171]) (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 73C582D9787 for ; Thu, 28 May 2026 23:01:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=61.135.153.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780009308; cv=none; b=H66SeEdzwTuH2SqHcg0tUVp377xqxelLuInqK2224cWQ8Nyx+bwx5dzhxIT7rytRMtV5PlI6hX4oVJ7GNbT8VieRPQOHK0IX9EMloCyp6e9npmgZTzSNbmRPZYgf+Qxf0kATitY1Nh8KIyn8gObtxVlbhFqWSIQcgNJYkD++U5w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780009308; c=relaxed/simple; bh=1T8/I6TvjiS18ZZDLJG7k3gfStyk9dmBa1e4cJe4Qtk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oziePcXtoQDj/GgR+wJKUVX/3VLVnlUu+Njmd5ewUnjcMwhl9xokx9f+8RS50Gxn8v1NFYHAY4aHjFpr8KEZ7YmM1EUZ+QtfTgkkBLOB3LgAt0g6G3dhpABbbqIpxI4owxY6V5lJC5cp9WmXeBfBI4G5URaKTRXTK8TizT0JUa0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com; spf=pass smtp.mailfrom=sina.com; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b=j3bh2zBo; arc=none smtp.client-ip=61.135.153.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sina.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b="j3bh2zBo" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sina.com; s=201208; t=1780009302; bh=ew4LKtHTQRw4JU9dPbT+Bkxy6WAebg2DDIpNh0S9wiE=; h=From:Subject:Date:Message-ID; b=j3bh2zBop3s2UXi2eDER1j43CzZ/29e4XHtwAYmjwhjKvZeEqIzphlqymomc01ngi 4jCg+4P9hs922NMUn9M9R1voKlxQhs9xM7gjHV1NH7cUiIQa9IQYVEeSimv4lgKWrs A1bpd2LRG7Xu5pmTTQpQca0h5g+JtbXzAhTqfUxM= X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([114.249.62.144]) by sina.com (10.54.253.34) with ESMTP id 6A18C92B0000506E; Thu, 29 May 2026 07:01:01 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 5580266291955 X-SMAIL-UIID: 978DE95D27164842A9C09416F2C93710-20260529-070101-1 From: Hillf Danton To: Ming Lei Cc: Tetsuo Handa , Jens Axboe , Bart Van Assche , Christoph Hellwig , Damien Le Moal , linux-block , LKML , Andrew Morton , Linus Torvalds , linux-btrfs@vger.kernel.org, David Sterba , linux-fsdevel@vger.kernel.org, Christian Brauner Subject: Re: [PATCH v3] loop: Fix NULL pointer dereference in lo_rw_aio() Date: Fri, 29 May 2026 07:00:47 +0800 Message-ID: <20260528230050.1185-1-hdanton@sina.com> In-Reply-To: <20260528054334.1159-1-hdanton@sina.com> References: Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Thu, 28 May 2026 13:43:31 +0800 Hillf Danton wrote: >On Tue, 26 May 2026 22:00:49 -0500 Ming Lei wrote: >>On Wed, May 27, 2026 at 10:35:56AM +0900, Tetsuo Handa wrote: >>> On 2026/05/27 10:20, Ming Lei wrote: >>> >> Of course we should try to figure out the root cause first, but how can we do? >>> > >>> > Definitely unexpected write IO(after umount & loop closed) from btrfs is more serious, >>> > which may cause data loss, so CC btrfs list and maintainer. >>> >>> Why do you assume that the culprit is btrfs? >>> >>> https://syzkaller.appspot.com/bug?extid=bc273027d5643e48e5b3 indicated that >>> this similar race is also happening with jfs. >> >> I just didn't see the above report on jfs. >> >> It doesn't change anything, the same question still stands: unexpected write IO is issued >> or crosses umount & last closing of loop disk. >> > Given the loop workqueue that triggered the jfs warning, can you specify > the reason why the workqueue in question is NOT flushed while closing disk? > Got it, the loop workqueue is NOT flushed to avoid deadlock, see d292dc80686a ("loop: don't destroy lo->workqueue in __loop_clr_fd") for detail. And the deadlock can be reproduced by flushing the loop workqueue with disk->open_mutex held [1]. [1] Subject: Re: [syzbot] possible deadlock in blkdev_put (3) https://lore.kernel.org/lkml/000000000000ea753505da2658d5@google.com/