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Date: Mon, 09 Sep 2002 14:47:25 -0700
From: Andrew Morton <akpm@digeo.com>
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To: Manfred Spraul <manfred@colorfullife.com>
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Subject: Re: Calculating kernel logical address ..
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Manfred Spraul wrote:
> 
> Andrew Morton wrote:
> > Nobody seems to have come forth to implement a thought-out scatter/gather,
> > map-user-pages library infrastructure so I'd be a bit reluctant to
> > break stuff without offering a replacement.
> >
> 
> We'd need one.
> 
> get_user_pages() is broken if a kernel module access the virtual address
> of the page and the cpu caches are not coherent:

OK.  Most users seem to just want to put the pages under DMA though.

> Most of the flush functions need the vma pointer, but it's impossible to
> guarantee that it still exists when the get_user_pages() user calls
> page_cache_release().

Well presumably, if the driver is altering user memory by hand,
it is synchronous and they can hang onto mmap_sem while doing it?
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