From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756051AbaCLSj2 (ORCPT ); Wed, 12 Mar 2014 14:39:28 -0400 Received: from mail-pa0-f54.google.com ([209.85.220.54]:46686 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755894AbaCLSjZ (ORCPT ); Wed, 12 Mar 2014 14:39:25 -0400 Message-ID: <1394649562.31499.202.camel@bobble.lax.corp.google.com> Subject: Re: [PATCH] block: Force sector and nr_sects to device alignment and granularity. From: Frank Mayhar To: Jeff Moyer Cc: Jens Axboe , linux-kernel , "Martin K. Petersen" , Theodore Tso Date: Wed, 12 Mar 2014 11:39:22 -0700 In-Reply-To: References: <1394474492.31499.177.camel@bobble.lax.corp.google.com> <1394553778.31499.180.camel@bobble.lax.corp.google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2014-03-12 at 14:20 -0400, Jeff Moyer wrote: > but you managed to read my mind well enough. The question is how high > up the stack do you put the logic for this? Is it worth it to duplicate > the checks in the OS that are already done on the device? I don't > know. Martin, do you have an opinion on this? Well, my opinion (and I suspect that Ted agrees with me to at least some extent) is that this is where it should be, i.e. in the block layer, in the place that already knows about and deals with alignment and granularity. Sure, you could leave it to the device itself but it seems reasonable to take care of this here for two reasons: First, doing this means that if a TRIM is issued it will be successful and the intent of the discard will be at least partly satisfied. Second, we're already doing most of the computations and making decisions based on the alignment and granularity anyway, so the overhead is pretty negligible (and if the discard size goes to zero we short-circuit the process and never go to the device at all). -- Frank Mayhar 310-460-4042