Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755915Ab1FBNsT (ORCPT ); Thu, 2 Jun 2011 09:48:19 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:46409 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754501Ab1FBNsR convert rfc822-to-8bit (ORCPT ); Thu, 2 Jun 2011 09:48:17 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=chromium.org; s=google; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=oJjBYVzzXzfMrOdt9esT2puOLfYkvA3zkuhtHAnBbsYkL8pJJpHucDj5my4f/6L12J DqRemVIhbTGamqA1XyCrBBE1TVWaxPob15BkwWpY/tk/tQim9+xJcCB9vM9fvjO2WDHq JLe8V4o+IFOGFcmggANvRyQVcVXciawpCFPSY= MIME-Version: 1.0 In-Reply-To: References: <1306957788-12310-1-git-send-email-wad@chromium.org> Date: Thu, 2 Jun 2011 08:48:16 -0500 Message-ID: Subject: Re: [PATCH] init: add root=PARTUUID=UUID+/-%d support From: Will Drewry To: Kay Sievers Cc: linux-kernel@vger.kernel.org, Jens Axboe , Andrew Morton , Namhyung Kim , Trond Myklebust 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: 2748 Lines: 57 On Thu, Jun 2, 2011 at 7:49 AM, Kay Sievers wrote: > On Wed, Jun 1, 2011 at 21:49, Will Drewry wrote: >> Not sure if this is practical and/or interesting to others, but it's a >> minimal change -- >> >> Expands root=PARTUUID=UUID syntax to support selecting a root partition >> by integer offset from a known, unique partition. ?This approach >> provides similar properties to specifying a device and partition number, >> but using the UUID as the unique path prior to evaluating the offset. >> >> For example, >> ?root=PARTUUID=99DE9194-FC15-4223-9192-FC243948F88B+1 >> selects the partition with UUID 99DE.. then select the next >> partition. >> >> This change is motivated by a particular usecase in Chromium OS where >> the bootloader can easily determine what partition it is on (by UUID) >> but doesn't perform general partition table walking. >> >> That said, support for this approach provides a direct mechanism for the >> user to modify the root partition to boot without specifically needing >> to extract each PARTUUID or update the bootloader explicitly when the >> root partition UUID is changed (if it is recreated to be larger, for >> instance, restored, etc). ?Pinning to a /boot partition UUID with an >> offset allows the arbitrary root partition reconfiguration/modifications >> with slightly less ambiguity than just [dev][partition] and less >> stringency than the specific root partition UUID. > > Kind of a creative notation to add/substract something from a uuid. :) Necessity can sometimes do that :) > If we are not sure we'll not need another magic thing in the future, > we might want to go for a named parameter to add? > Maybe instead of: > ?root=PARTUUID=99DE9194-FC15-4223-9192-FC243948F88B+2 > we could do: > ?root=PARTUUID=99DE9194-FC15-4223-9192-FC243948F88B,PARTNROFF=2 > > Might be it's a but over the top, but the key is named PARTUUID, and a > +- to it doesn't seem to explain what it does and can not really be > expanded for even more creative uses. :) Good call! I'll take a pass at integrating that. I can see a couple different ways of handling the parsing (e.g., when and what does it affect). Do you think it would make sense to keep it isolated to just being a PARTUUID subargument or would it make more sense for PARTNROFF= to be evaluated as a generic root= attribute? I can see benefits to both, but one is considerably more minimal to implement :) [Maybe I'll try both and see how they look.] thanks! -- 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/