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 7C71BCF2560 for ; Tue, 18 Nov 2025 23:11:00 +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=rzPEj4eurnkGH9Ev1raz8nnyXgF/BqMIBftE0wJlaYE=; b=OnXHxF/zSdu9LfFEegcspY824t QnICP4hnFpe4Kc28daranC875i46QqcWsiiwohv0su2LmLEQPs5/MwliEo6LLAU49JusKCYcYnavN z8Kg2FXU3TIkdWFyXwtYxbr2+zwhHzPiJBcq0/Hs8beVrsu3kgenRUvVTym7PpvBQFjn5fpOipVik xsSX92iwTXjL+I+4AqTl6XOYP5TzVHp3dDasB/ipK+t7y8IZiaF21i5hl0kuAZcHBJtsT14GSldY2 6ifGUCTcm8D1V+D956OxDvAeREK15JNdBxLGiO3157i6UW1N+Y41Q36gWm+MQ3avc0/Dpx3t1FfaV q19FgUMg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vLUqe-00000001Dit-0Jg1; Tue, 18 Nov 2025 23:10:56 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vLUqc-00000001Dic-1tVw for linux-nvme@lists.infradead.org; Tue, 18 Nov 2025 23:10:54 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 88FED6014A; Tue, 18 Nov 2025 23:10:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 262B5C2BC86; Tue, 18 Nov 2025 23:10:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763507452; bh=7QQygTuOQynkohM3s2IldwIWULLZl54zzYKbrbFD0h8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bjl6TzrpZsV04eh6v4kBgSjuImsUEm9WB8cKFVv14EuRtklHdlW51lAuUidl0puBT /IF5mdPC3JYaXh8luXYGEmHJQo6wAyvmAkXCf0uDKs/u1yPKSB3EC5rRQ6qmwZWhyx FaDwU0h5JeIWJPU53QMFBRrhcdrYcLXS3EIyuLJTvuLMl/vXie8Kgsa9IFsKIUy0GO /h8GD/lqiNP4ZMu8+UmzWPn6pK8NKXbje/eKaBBlPAveJaAP6m1psqUscXnmTOWsik C89DuwxDNpGBXHoLLilCTvrfvxfD5l29AztFyNNomSnF5rTmkbcSzkWnn8HjY+SvPO KhHFFIK87Wpdg== Date: Tue, 18 Nov 2025 16:10:48 -0700 From: Keith Busch To: Christoph Hellwig Cc: Leon Romanovsky , Jens Axboe , Sagi Grimberg , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Chaitanya Kulkarni Subject: Re: [PATCH v2 1/2] nvme-pci: Use size_t for length fields to handle larger sizes Message-ID: References: <20251117-nvme-phys-types-v2-0-c75a60a2c468@nvidia.com> <20251117-nvme-phys-types-v2-1-c75a60a2c468@nvidia.com> <20251118051823.GA21858@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251118051823.GA21858@lst.de> 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 Tue, Nov 18, 2025 at 06:18:23AM +0100, Christoph Hellwig wrote: > On Mon, Nov 17, 2025 at 12:35:40PM -0700, Keith Busch wrote: > > > + size_t total_len; > > > > Changing the generic phys_vec sounds fine, but the nvme driver has a 8MB > > limitation on how large an IO can be, so I don't think the driver's > > length needs to match the phys_vec type. > > With the new dma mapping interface we could lift that limits for > SGL-based controllers as we basically only have a nr_segments limit now. > Not that I'm trying to argue for multi-GB I/O.. It's not a bad idea. The tricky part is in the timeout handling. If we allow very large IO, I think we need a dynamic timeout value to account for the link's throughput. We can already trigger blk-mq timeouts if you saturate enough queues with max sized IO, despite everything else working-as-designed.