From mboxrd@z Thu Jan 1 00:00:00 1970 From: "John Stoffel" Subject: Re: [PATCH] md/raid0: add config parameters to specify zone layout Date: Thu, 30 Apr 2020 12:09:49 -0400 Message-ID: <24234.63565.561786.818825@quad.stoffel.home> References: <1585236500-12015-1-git-send-email-jbaron@akamai.com> <0b7aad8b-f0b7-24c6-ad19-99c6202a3036@suse.de> <8feb2018-7f99-6e02-c704-9d7fed40bba2@akamai.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Song Liu Cc: Jason Baron , Coly Li , "agk@redhat.com" , "snitzer@redhat.com" , "linux-raid@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Guoqing Jiang , NeilBrown List-Id: linux-raid.ids >>>>> "Song" == Song Liu writes: Song> Hi Jason, >> On Apr 27, 2020, at 2:10 PM, Jason Baron wrote: >> >> >> >> On 4/25/20 12:31 AM, Coly Li wrote: >>> On 2020/3/26 23:28, Jason Baron wrote: >>>> Let's add some CONFIG_* options to directly configure the raid0 layout >>>> if you know in advance how your raid0 array was created. This can be >>>> simpler than having to manage module or kernel command-line parameters. >>>> >>> >>> Hi Jason, >>> >>> If the people who compiling the kernel is not the end users, the >>> communication gap has potential risk to make users to use a different >>> layout for existing raid0 array after a kernel upgrade. >>> >>> If this patch goes into upstream, it is very probably such risky >>> situation may happen. >>> >>> The purpose of adding default_layout is to let *end user* to be aware of >>> they layout when they use difference sizes component disks to assemble >>> the raid0 array, and make decision which layout algorithm should be >>> used. Such situation cannot be decided in kernel compiling time. >> >> I agree that in general it may not be known at compile time. Thus, >> I've left the default as RAID0_LAYOUT_NONE. However, there are >> use-cases where it is known at compile-time which layout is needed. >> In our use-case, we knew that we didn't have any pre-3.14 raid0 >> arrays. Thus, we can safely set RAID0_ALT_MULTIZONE_LAYOUT. So >> this is a simpler configuration for us than setting module or command >> line parameters. Song> I would echo Coly's concern that CONFIG_ option could make it risky. Song> If the overhead of maintaining extra command line parameter, I would Song> recommend you carry a private patch for this change. For upstream, it Song> is better NOT to carry the default in CONFIG_. I agree as well. Just because you have a known base, doesn't mean that others wouldn't be hit with this problem. John