From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx180.postini.com [74.125.245.180]) by kanga.kvack.org (Postfix) with SMTP id 677F76B0005 for ; Tue, 12 Feb 2013 16:57:28 -0500 (EST) Date: Tue, 12 Feb 2013 13:57:26 -0800 From: Andrew Morton Subject: Re: [PATCH] mm: export mmu notifier invalidates Message-Id: <20130212135726.a40ff76f.akpm@linux-foundation.org> In-Reply-To: <20130212213534.GA5052@sgi.com> References: <20130212213534.GA5052@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Cliff Wickman Cc: linux-mm@kvack.org, aarcange@redhat.com, mgorman@suse.de On Tue, 12 Feb 2013 15:35:34 -0600 Cliff Wickman wrote: > > Commenting on this patch ended with Andrea's post on 07Jan, which was > a more-or-less endorsement and a question about support for extended vma > abstractions in kernel modules out of tree. > (that comment can be found at http://marc.info/?l=linux-mm&m=135757292605395&w=2) > > I'd like to make the request again to consider export of these two symbols. > > > We at SGI have a need to address some very high physical address ranges with > our GRU (global reference unit), sometimes across partitioned machine boundaries > and sometimes with larger addresses than the cpu supports. > We do this with the aid of our own 'extended vma' module which mimics the vma. > When something (either unmap or exit) frees an 'extended vma' we use the mmu > notifiers to clean them up. > > We had been able to mimic the functions __mmu_notifier_invalidate_range_start() > and __mmu_notifier_invalidate_range_end() by locking the per-mm lock and > walking the per-mm notifier list. But with the change to a global srcu > lock (static in mmu_notifier.c) we can no longer do that. Our module has > no access to that lock. > > So we request that these two functions be exported. > > ... > > +EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start); > +EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end); erk. Having remote, modular, out-of-tree *sending* mmu notifications is pretty abusive :( I don't have a problem with the patch personally. It's a GPL export and it's only 2 lines and if we break it, you own both pieces ;) But in a better world, the core kernel would support your machines adequately and you wouldn't need to maintain that out-of-tree MM code. What are the prospects of this? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org