From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 0C0C12BD10; Mon, 3 Feb 2025 08:30:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738571418; cv=none; b=cOmIB98TVEgS6xEGj+xA4iDxaCrU1FT0DTrI6qN7U7masucf2+3lEkMWhsfZaErv//+3qE0XRtDeXdE5fhE3PDCto29PFMSt/2GogfC9U2baEAiONH2Y/cMpXtm39Oknj5mRo4WQuqROt+ejqIwRpkRz/9o+xRIBS7tPJag43L0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738571418; c=relaxed/simple; bh=3cO4qyclNc033Cj6ZmMnLChbflbiN24MN5QRcDeuegQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aqrzQA6DCzdqhjNtvtXlyyiZaOD60lha76RZESXtUCndewQKOkIEjN6vudPzeFwMlSM7EIQwCqOfXjyS2ZJvDq24dASzzJyN6IvCE47IdoZmARh2yGccxACPXFrtuG2WcmWWngJfaoiqpv8e8iCxBBoq8YbnsMq+3Ta4HqX+xbs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=XrHj1Q1e; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="XrHj1Q1e" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=GEeRARndOURU601MNaUwqkzgOLPL0RKLmzvNkf3CvH8=; b=XrHj1Q1eHOUdOfUOVDAHT0Q+1d QBl8BI1PJ9841YOZjOxYpvq5BaS6vsN2/94VlcjmiVRLDfWKYArcYxscCdLix7kecyROoHpgRdIEJ 2EpKbYV0YqZP4gk5HwXpWVMSjlRayadY0WswozBUqAtmDHfr2ySZN3OimPJxuAGE9EkGE+iUpTmUv gbAIaIHaOpRe/6/LO4ZHVeB19myKg673K2JCzuu9ZMeaSSjnqCMA9rYUHOiGO1ka2yaI7Kl4KpCYY Dj+2ShximPp3CRnGgpECevEnrObzSjcB+Oj6zJHZpqX0aQaD/DhB6v8V9n9GJyZc18hb9vOlxcGgg Tx5nfBww==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1terqQ-0000000EqEQ-1Jdo; Mon, 03 Feb 2025 08:30:14 +0000 Date: Mon, 3 Feb 2025 00:30:14 -0800 From: "hch@infradead.org" To: Matthew Wilcox Cc: Qu Wenruo , Johannes Thumshirn , "hch@infradead.org" , Kanchan Joshi , Theodore Ts'o , "lsf-pc@lists.linux-foundation.org" , "linux-btrfs@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-block@vger.kernel.org" , "josef@toxicpanda.com" Subject: Re: [LSF/MM/BPF TOPIC] File system checksum offload Message-ID: References: <20250130091545.66573-1-joshi.k@samsung.com> <20250130142857.GB401886@mit.edu> <97f402bc-4029-48d4-bd03-80af5b799d04@samsung.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Mon, Feb 03, 2025 at 08:26:33AM +0000, Matthew Wilcox wrote: > so this is a block layer issue if it's not set. And even if the flag is set direct I/O ignores it. So while passing through such a flag through virtio might be useful we need to eventually sort out the fact that direct I/O doesn't respect it. Locking up any thread touching memory under direct I/O might be quite heavy handed, so this means bounce buffering on page fault. We had plenty of discussion of this before, but I don't think anyone actually looked into implementing it.