Oh, you misunderstand.. (probably because I'm unclear)
I'm not saying that getting a page from a user space mapping is bad: a lot
of places do that independently of zero-copy.
But hopefully nobody should have the problematic last reference to a LRU
page _except_ the user space itself. That should be safe for page cache
pages thanks to the truncate change.
And for anonymous pages, I really think that the right solution is to do
the same remove-from-LRU thing for the "last unmap" (which should be
trivial to notice with rmap).
I'm trying to come up with what kept us safe in 2.4.x for anonymous pages,
and I get this sinking feeling that we really aren't.
Which may imply that Andrew's irq-safe LRU list is the right thing to do
after all. At least on 2.4.x (and if you do it there, then my arguments
about it being unnecessary on 2.5.x due to "design" just totally cruble
away, since clearly Andrew was rigth and the "design argument" was total
Let me sleep on this. Does anybody have any intelligent thoughts?
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