From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from verein.lst.de ([213.95.11.211]:35721 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751704AbcADQjw (ORCPT ); Mon, 4 Jan 2016 11:39:52 -0500 Date: Mon, 4 Jan 2016 17:39:50 +0100 From: Christoph Hellwig To: Sagi Grimberg Cc: Christoph Hellwig , viro@zeniv.linux.org.uk, axboe@fb.com, milosz@adfin.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: selective block polling and preadv2/pwritev2 revisited Message-ID: <20160104163949.GA17409@lst.de> References: <1450966464-6847-1-git-send-email-hch@lst.de> <568A889E.4020204@dev.mellanox.co.il> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <568A889E.4020204@dev.mellanox.co.il> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Jan 04, 2016 at 04:58:38PM +0200, Sagi Grimberg wrote: > Hi Christoph, > >> Note that there are plenty of other use cases for preadv2/pwritev2 as well, >> but I'd like to concentrate on this one for now. Example are: non-blocking >> reads (the original purpose), per-I/O O_SYNC, user space support for T10 >> DIF/DIX applications tags and probably some more. > > So I'm trying to understand how can integrity metadata be used here. > Will the user-app append the meta-data to the data iovec (given there > is no metadata iovec)? If so, how will we separate data from metadata? The idea that was floated aroud a few times was to have a flag where the first half of the vectors would be the data, and the second half the metadata.