Hi Jason, > On Apr 27, 2020, at 2:10 PM, Jason Baron <jbaron@xxxxxxxxxx> 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. I would echo Coly's concern that CONFIG_ option could make it risky. 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
