From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: Re: selective block polling and preadv2/pwritev2 revisited Date: Wed, 6 Jan 2016 19:01:13 +0200 Message-ID: <568D4859.4010206@dev.mellanox.co.il> References: <1450966464-6847-1-git-send-email-hch@lst.de> <568A889E.4020204@dev.mellanox.co.il> <20160104163949.GA17409@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160104163949.GA17409-jcswGhMUV9g@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Christoph Hellwig Cc: viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org, axboe-b10kYP2dOMg@public.gmane.org, milosz-B5zB6C1i6pkAvxtiuMwx3w@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org >> 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. This means that the user would need to pass iovec entries of 8 bytes correct? Seems like a waste for large IOs (sorry for diverging from the subject) From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f49.google.com ([74.125.82.49]:33224 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751755AbcAFRBS (ORCPT ); Wed, 6 Jan 2016 12:01:18 -0500 Received: by mail-wm0-f49.google.com with SMTP id f206so67088381wmf.0 for ; Wed, 06 Jan 2016 09:01:17 -0800 (PST) Subject: Re: selective block polling and preadv2/pwritev2 revisited To: Christoph Hellwig References: <1450966464-6847-1-git-send-email-hch@lst.de> <568A889E.4020204@dev.mellanox.co.il> <20160104163949.GA17409@lst.de> Cc: 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 From: Sagi Grimberg Message-ID: <568D4859.4010206@dev.mellanox.co.il> Date: Wed, 6 Jan 2016 19:01:13 +0200 MIME-Version: 1.0 In-Reply-To: <20160104163949.GA17409@lst.de> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: >> 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. This means that the user would need to pass iovec entries of 8 bytes correct? Seems like a waste for large IOs (sorry for diverging from the subject)