Quoting Hugh Dickins <[email protected]>:
> Two warnings if someone would like to post a MADV_DONTCOPY patch.
> It should include a matching MADV_DOCOPY to clear the condition, but
> that must not be allowed to clear VM_DONTCOPY set originally by driver:
> perhaps you'll end up with a VM_UDONTCOPY or something like that.
Thanks!
All existing drivers that set VM_DONTCOPY also set VM_IO.
So lets just disable playing with these flags from madvise if VM_IO is set.
There's no reason I can see that the driver should have a say
on what the process does with its own (non-IO) memory.
Sounds good?
By the way, as a separate issue, we still have a problem with DMA to pages
which are *needed* by the child process. What do you think about VM_COPY
(to do the old unix thing of actually copying the page instead of
setting the COW flag) and a matching madvise call to set/clear it?
> And Badari has a MADV_REMOVE patch in the works, taking the next
> slot (just after MADV_DONTNEED in most of the arches): probably
> best for you to base yours on top of his (though yours is simpler
> and might jump ahead).
>
> Hugh
Yep, I saw that posted for inclusion in -mm.
--
MST
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