Messages in this thread | | | Date | Tue, 17 Oct 2000 00:49:19 +0200 | From | Andrea Arcangeli <> | Subject | Re: mapping user space buffer to kernel address space |
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On Mon, Oct 16, 2000 at 02:59:59PM -0700, Linus Torvalds wrote: > No. Because "pinning" is _stupid_.
Pinning using map_user_kiobuf looks just the other way around of what we do usually with the mmap callback of the device driver and remap_page_range. I considered "pinning" just to convert the user page to one of the pages mapped with remap_page_range so they can threat them in the same way internally in the device driver (and the ones mapped with remap_page_range don't get unmapped and then into swap of course).
> Instead, the Linux answer is to say: pinning is bad, pinning is stupid, > pinning is useless - so dont do it.
So just delete map_user_kiobuf from your tree if people shouldn't do it. That would fix the mm corruption too indeed. I don't see why you provide that functionality and then you keep telling people not to use it. Also rawio and networking could use the other way around. I think that's mainly a matter of API. People is used to think in read/write terms. And infact rawio doesn't provide a completly transpartent read/write because it have constrants on the buffer alignment.
If you won't delete map_user_kiobuf from your tree I think I've just provided a real world MM corruption case where the user send the bug report back to us if we only increase the reference count of the page to pin it.
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