From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 013.lax.mailroute.net (013.lax.mailroute.net [199.89.1.16]) (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 A809E394462; Mon, 24 Aug 2026 22:54:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=199.89.1.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787612047; cv=none; b=SOZzIhNqWMGm5dUiXAS/gt2kt1yivBzEpweZHViCVeukjbwyyW23VZI5fhLLEgTaDkjbqQ/Jw853bddY2lADkqIomSLg26MIhS4lqBWDn0cl6puURr6aD3coCgZQ4Ea/NkEj91RDg1oJguxNqDaXMYCGcMm731CTasDHcSovh/g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787612047; c=relaxed/simple; bh=fIEAMrSn9qVQ98whfUHmurKZ4stg2V53zJ0ACfdmkeQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=E2TvJ5125b8QEBgTxXt0l+T16f3ZWL3GH6Po5z7EL89sRxhz8bTaeex5hpHZzSi9IfPBBSH6i2ysy1UB7d8t9loYkCF3vJirnlPnkxMG6B50X3JaJIGk2fHJukHWgO2AaOkc7SG0zRPeqQ4DVxAvhM/KGwtW+XGQu1oKGTjZXxA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org; spf=pass smtp.mailfrom=acm.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b=kUqnjA6H; arc=none smtp.client-ip=199.89.1.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=acm.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b="kUqnjA6H" Received: from localhost (localhost [127.0.0.1]) by 013.lax.mailroute.net (Postfix) with ESMTP id 4hTR6h757LzlfwgD; Mon, 24 Aug 2026 22:54:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=acm.org; h= content-transfer-encoding:content-type:content-type:in-reply-to :from:from:content-language:references:subject:subject :user-agent:mime-version:date:date:message-id:received:received; s=mr01; t=1787612036; x=1790204037; bh=fIEAMrSn9qVQ98whfUHmurKZ 4stg2V53zJ0ACfdmkeQ=; b=kUqnjA6H9nOu4wBYMHnD7nwetgrycZRz51bh5y/0 zH+m1DmsVM5A0DCd7qxFTgXiLlLv+KUD9zt4qa5PBc770BaMXnZFbUxUqx4MW+sR 6XcFqztDi1bYRJ4cf+N1SOlqOd8btwrlPsyU+vYGh++wTY7eLQ9ec7fvOTvmpcM/ H5wV3P6DBUy1Fj4soCOKKPx6dxgrKf/pFJpXK73tCXLWDSkjmX9GdZeIMda3zjXa 2JInEovsFqJupAZBtZUgFCkLCdZPx/OEe7QVgN1bsGGK7cLDUizDGFyi8wGRafFd TDE6tcjBYGVZWFR7wnnNBqWH5PjjOO4fTLJp0o9HH5fAPg== X-Virus-Scanned: by MailRoute Received: from 013.lax.mailroute.net ([127.0.0.1]) by localhost (013.lax [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id 7GE_wI3mRROZ; Mon, 24 Aug 2026 22:53:56 +0000 (UTC) Received: from [100.80.227.50] (unknown [104.135.182.42]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bvanassche@acm.org) by 013.lax.mailroute.net (Postfix) with ESMTPSA id 4hTR6Q6ZQbzlfvq9; Mon, 24 Aug 2026 22:53:50 +0000 (UTC) Message-ID: <372ca5f6-81a0-4f6c-8f55-ebeeada9f955@acm.org> Date: Mon, 24 Aug 2026 15:53:49 -0700 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6] loop: Fix NULL pointer dereference in lo_rw_aio() To: Tetsuo Handa , Markus Elfring , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Alexander Viro , Damien Le Moal , Jens Axboe Cc: linux-kernel@vger.kernel.org, linux-next@vger.kernel.org, lkp@intel.com, oe-lkp@lists.linux.dev, Christian Brauner , Christoph Hellwig , Christoph Hellwig , Hillf Danton , Linus Torvalds , Mark Brown , Oliver Sang References: <8dedfc40-9cae-44ff-9960-e0eb1825e963@I-love.SAKURA.ne.jp> <550ff0b4-df39-46d2-9781-c8688df10c93@web.de> <38ad64c1-edc7-431d-8f52-fba572ebf3eb@I-love.SAKURA.ne.jp> Content-Language: en-US From: Bart Van Assche In-Reply-To: <38ad64c1-edc7-431d-8f52-fba572ebf3eb@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/24/26 3:06 PM, Tetsuo Handa wrote: > but sashiko found problems with Bart's series ( https://sashiko.dev/ > #/patchset/8330ca0e-b4d9-451a-bc0d-a50178194ea8@I-love.SAKURA.ne.jp > and https://sashiko.dev/#/patchset/2efb1032-34b9-4c31- > b6fc-4aa9b1d60895@I-love.SAKURA.ne.jp ). Thanks, I had not yet seen this feedback from Sashiko. My conclusion is that two of the three Sashiko findings are wrong. I will fix the third one - the finding about the potential wait-die deadlock. > I still cannot catch why Bart's approach can become safe without > synchronize_rcu() and drain_workqueue(). Agreed that drain_workqueue() or flush_workqueue() is necessary. I do not agree that an explicit synchronize_rcu() call is required. Waiting until the request queue is frozen includes this call implicitly. See also __percpu_ref_switch_to_atomic(). Thanks, Bart.