From mboxrd@z Thu Jan 1 00:00:00 1970 From: Song Liu Subject: Re: [PATCH] md/raid0: add config parameters to specify zone layout Date: Thu, 30 Apr 2020 06:19:26 +0000 Message-ID: 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: quoted-printable Return-path: In-Reply-To: <8feb2018-7f99-6e02-c704-9d7fed40bba2@akamai.com> Content-Language: en-US Content-ID: Sender: linux-kernel-owner@vger.kernel.org To: Jason Baron Cc: 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 Hi Jason, > On Apr 27, 2020, at 2:10 PM, Jason Baron wrote: >=20 >=20 >=20 > 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. >>>=20 >>=20 >> Hi Jason, >>=20 >> 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. >>=20 >> If this patch goes into upstream, it is very probably such risky >> situation may happen. >>=20 >> 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. >=20 > 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. I would echo Coly's concern that CONFIG_ option could make it risky.=20 If the overhead of maintaining extra command line parameter, I would recommend you carry a private patch for this change. For upstream, it is better NOT to carry the default in CONFIG_. Thanks, Song