Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754761Ab1E0M7d (ORCPT ); Fri, 27 May 2011 08:59:33 -0400 Received: from mail-iy0-f174.google.com ([209.85.210.174]:53351 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753536Ab1E0M7c convert rfc822-to-8bit (ORCPT ); Fri, 27 May 2011 08:59:32 -0400 MIME-Version: 1.0 In-Reply-To: <1306476003-4624-3-git-send-email-namhyung@gmail.com> References: <1306476003-4624-1-git-send-email-namhyung@gmail.com> <1306476003-4624-3-git-send-email-namhyung@gmail.com> Date: Fri, 27 May 2011 08:59:31 -0400 Message-ID: Subject: Re: [PATCH 3/3] nbd: adjust 'max_part' according to part_shift From: Paul Clements To: Namhyung Kim Cc: Jens Axboe , linux-kernel@vger.kernel.org, Laurent Vivier Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2069 Lines: 59 On Fri, May 27, 2011 at 2:00 AM, Namhyung Kim wrote: > The 'max_part' parameter determines how many partitions are supported > on each nbd device. However the actual number can be changed to the > power of 2 minus 1 form during the module initialization as > alloc_disk() is called with (1 << part_shift) for some reason. > > So adjust 'max_part' also at least for consistency with loop and brd. > It is exported via sysfs already, and a user should check this value > after module loading if [s]he wants to use that number correctly > (i.e. fdisk or something). > > Signed-off-by: Namhyung Kim > Cc: Laurent Vivier > Cc: Paul Clements Sure, looks good. Thanks, Paul > --- > ?drivers/block/nbd.c | ? 13 ++++++++++++- > ?1 files changed, 12 insertions(+), 1 deletions(-) > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > index fdee7567fd15..f533f3375e24 100644 > --- a/drivers/block/nbd.c > +++ b/drivers/block/nbd.c > @@ -754,9 +754,20 @@ static int __init nbd_init(void) > ? ? ? ? ? ? ? ?return -ENOMEM; > > ? ? ? ?part_shift = 0; > - ? ? ? if (max_part > 0) > + ? ? ? if (max_part > 0) { > ? ? ? ? ? ? ? ?part_shift = fls(max_part); > > + ? ? ? ? ? ? ? /* > + ? ? ? ? ? ? ? ?* Adjust max_part according to part_shift as it is exported > + ? ? ? ? ? ? ? ?* to user space so that user can know the max number of > + ? ? ? ? ? ? ? ?* partition kernel should be able to manage. > + ? ? ? ? ? ? ? ?* > + ? ? ? ? ? ? ? ?* Note that -1 is required because partition 0 is reserved > + ? ? ? ? ? ? ? ?* for the whole disk. > + ? ? ? ? ? ? ? ?*/ > + ? ? ? ? ? ? ? max_part = (1UL << part_shift) - 1; > + ? ? ? } > + > ? ? ? ?if ((1UL << part_shift) > DISK_MAX_PARTS) > ? ? ? ? ? ? ? ?return -EINVAL; > > -- > 1.7.5.2 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/