Re: [Qemu-devel] [PATCH V9 01/14] block: move bdrv_snapshot_find() to block/snapshot.c

[Markus Armbruster]

Kevin Wolf <address@hidden> writes:

> Am 13.03.2013 um 19:19 hat Markus Armbruster geschrieben:
>> Kevin Wolf <address@hidden> writes:
>> 
>> > Am 12.03.2013 um 06:01 hat Wenchao Xia geschrieben:
>> >>   Oops, Since it belongs to block layer I hope it can be LGPL2. Do you
>> >> know how to contact Fabrice Bellard to ask for a change?
>> >
>> > Fabrice is not the only copyright owner of this file.
>> >
>> > Just copy the license as it is, changing licenses is always a nasty
>> > thing and as I'm not a lawyer I prefer to stay on the safe side. The MIT
>> > license works well enough, there's no real reason to change it.
>> 
>> *Relicensing* a file is indeed "nasty" in the sense that it's a huge
>> hassle: you have to track down all copyright holders and get their
>> permission.
>> 
>> But this isn't relicensing.  This is exercising your *right* to
>> incorporate permissively-licensed stuff into work covered by a
>> compatible, stronger license.  That right was irrevocably granted to you
>> by the copyright holders.  You don't have to ask anyone to exercise it.
>
> But you have to do it right. This specific patch would introduce a
> copyright violation. It's really not that hard to conform to the terms
> of the MIT license, but that doesn't mean that you can ignore it. There
> is exactly one requirement and it reads like this:
>
>   The above copyright notice and this permission notice shall be
>   included in all copies or substantial portions of the Software.

That's why I pointed to resources and examples on how to do it properly.

> (I'm still waiting for a patch to blockdev.c, for which you did it
> wrong, by the way)

Oops, that one fell through the cracks.  Patch coming.

>> Of course, the stronger license still has to be compatible with GPLv2,
>> so we can accept the result into QEMU.
>> 
>> If a subsystem has additional requirements on licenses, its maintainers
>> will explain them to you.  For what it's worth, substantial parts of the
>> block layer are already GPLv2+.
>
> What parts exactly? As long as there are plans for a libqblock and as
> long as it doesn't seem completely impossible to have it under LGPL, I
> will ask to use either MIT or LGPL for block layer code (this doesn't
> apply to qemu-only code that isn't used in the tools - in this sense,
> things like blockdev.c are not part of the block layer)

$ git-grep -lw GPL block block*
block-migration.c
block/blkverify.c
block/gluster.c
block/linux-aio.c
block/raw-aio.h
block/rbd.c
block/sheepdog.c
blockdev-nbd.c
blockdev.c

>> You don't *have* to switch to a stronger license, of course.  It's your
>> choice.  Myself, I prefer to protect any substantial work I do with a
>> strong copyleft license such as GPLv2+.
>
> And it's my choice if I accept a patch that does nothing except moving
> code and switching to a stronger license. It feels wrong to do this,
> even though it may be legal. If you want to change the license for
> whatever reason, you should at least add substantial code of your own to
> justify this.

I wouldn't submit such a patch.  Not everything that's legal is proper.