There _is_ a major problem: being able to swap out page tables means that
the thing that swaps them out _has_ to own the mm semaphore.
That's the right thing to do anyway, but it means, for example, that the
_only_ process that can page stuff out would be kswapd.
Who knows? Maybe I should just bite the bullet and make that the rule,
then we could forget about all the extra recursive semaphore crap too. And
it has other advantages - it can speed up the page fault handler (which
right now has to get the kernel lock for certain situations).
Once that is done, paging out page tables is not really a problem.
> There are real cases where grab large linear block is needed.
Nobody has so far shown a reasonable implementation where this would be
possible.
Linus
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