Re: [PATCH] mm: Add new vma flag VM_LOCAL_CPU

From: Matthew Wilcox <willy@infradead.org>
To: Boaz Harrosh <boazh@netapp.com>
Cc: Jeff Moyer <jmoyer@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Rik van Riel <riel@redhat.com>, Jan Kara <jack@suse.cz>,
	Matthew Wilcox <mawilcox@microsoft.com>,
	Amit Golander <Amit.Golander@netapp.com>
Subject: Re: [PATCH] mm: Add new vma flag VM_LOCAL_CPU
Date: Tue, 15 May 2018 06:50:56 -0700	[thread overview]
Message-ID: <20180515135056.GG31599@bombadil.infradead.org> (raw)
In-Reply-To: <afe2c02f-3ecd-5f54-53ab-d45c11a5b4aa@netapp.com>

On Tue, May 15, 2018 at 04:29:22PM +0300, Boaz Harrosh wrote:
> On 15/05/18 15:03, Matthew Wilcox wrote:
> > You're getting dangerously close to admitting that the entire point
> > of this exercise is so that you can link non-GPL NetApp code into the
> > kernel in clear violation of the GPL.
> 
> It is not that at all. What I'm trying to do is enable a zero-copy,
> synchronous, low latency, low overhead. highly parallel - a new modern
> interface with application servers.

... and fully buzzword compliant.

> You yourself had such a project that could easily be served out-of-the-box
> with zufs, of a device that wanted to sit in user-mode.

For a very different reason.  I think the source code to that project
is publically available; the problem is that it's not written in C.

> Sometimes it is very convenient and needed for Servers to sit in
> user-mode. And this interface allows that. And it is not always
> a licensing thing. Though yes licensing is also an issue sometimes.
> It is the reality we are living in.
> 
> But please indulge me I am curious how the point of signing /sbin/
> servers, made you think about GPL licensing issues?
> 
> That said, is your point that as long as user-mode servers are sloooowwww
> they are OK to be supported but if they are as fast as the kernel,
> (as demonstrated a zufs based FS was faster then xfs-dax on same pmem)
> Then it is a GPL violation?

No.  Read what Linus wrote:

   NOTE! This copyright does *not* cover user programs that use kernel
 services by normal system calls - this is merely considered normal use
 of the kernel, and does *not* fall under the heading of "derived work".

What you're doing is far beyond that exception.  You're developing in
concert a userspace and kernel component, and claiming that the GPL does
not apply to the userspace component.  I'm not a lawyer, but you're on
very thin ice.