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 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.lore.kernel.org (Postfix) with ESMTPS id 0BBC5C02196 for ; Mon, 3 Feb 2025 08:31:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=GEeRARndOURU601MNaUwqkzgOLPL0RKLmzvNkf3CvH8=; b=LWHnwb3hgKMx2WRrV9CKnSkAmm VV6p6XvoMaj6/TtYt4WbRjACxEMstpFuJJL6nKymvQZuaUSe419EWMSrEa6CsjwyLru/tuoyYxOii Cn7FDvJwI72jIjEtJ7tfXKIotb2xf/Z+ehknOyZeZ6+2GTUhQAfMTNxtTTPXXBUmsM9YG8Jh/qQEx 6r9Du0mmXd5KKq60H4JJRzrMtoNG0Oeb/Rp46O86++G20zmevtglfMSazHFsV1ocFzotCk5XyjyXM J/bdWDkFhCe0paeXdHe77uUziCpE/w7isQoY7Rpu8rkVUk2fbtIWhhPo9o/mGoSC/aQmU2EC3gge+ 3WSBVwlQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1terrT-0000000EqNk-1LWr; Mon, 03 Feb 2025 08:31:19 +0000 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org 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.