Re: mapping user space buffer to kernel address space

[Andrea Arcangeli]

On Tue, Oct 17, 2000 at 12:27:30PM -0700, David S. Miller wrote:
> Hint: smp_flush_tlb_page()
> 
> Current kiobufs never need to do that, under any circumstances.
> This is not by accident.

I don't understand. flush_tlb_page() done in the context of a thread won't care
about the state of the physical page. I don't see how it's related to kiobufs.

> I don't see what the big deal is in requiring that user applications
> do their own locking to protect page contents being modified in one
> thread while a direct I/O from it is happening in another thread.  I

We never talked about this issue in the previous emails. That is required
regardless of how we solve the MM corruption.

> also don't see why any bug with kiobufs can't be fixed without the
> expensive and complex pinning.

IMHO pinning the page in the pte is less expensive and less complex than making
rawio and the VM aware of those issues. (remap_page_range is so clean
implementation exactly because it pins the page into the pte)

Andrea
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