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SubjectRe: [PATCH 4/4] FUSE: implement direct mmap
FromMiklos Szeredi <>
DateMon, 06 Jul 2009 13:41:12 +0200
On Sat, 04 Jul 2009, Tejun Heo wrote:
> > Afaics sound drivers now map the dma memory with remap_pfn_range().
> > Similary we could allocate a chunk of non-swapabble kernel memory on
> > request from the userspace server and map its pages using this trick
> > to both the server's and the client's address space.
> >
> > This is still sort of OSSP specific, I don't see clearly how it could
> > be made more generic.
>
> Using non-swappable memory would be fine for most device emulations
> but mapping large amount of pages would be problematic. Hmmm... this
> is difficult. It's a compromise among flexibility, scalability and
> code complexity.

What's the difficulty?

Allocating pages, giving them an ID and mapping them into various page
tables seems simple in contrast to trying to make a tmpfs file be a
fuse file at the same time, which the VM is really not prepared for.

Thanks,
Miklos


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