Benjamin Herrenschmidt wrote:
I have no problem keeping PG_reserved for that, and _ONLY_ for that.
(though i'd rather see it renamed then). I'm just afraid by doing so,
some drivers will jump in the gap and abuse it again...
Sure it would be renamed (better yet may be a slower page_is_valid()
that doesn't need to use a flag).
There is always the possibility for driver abuse, I guess... however
as it is now, the tree is basically past the critical mass of self
perpetuation (ie. cut-n-paste). So getting rid of that should certianly
help get things cleaner.
Also, we should
make sure we kill the "trick" of refcounting only in one direction.
Either we refcount both (but do nothing, or maybe just BUG_ON if the
page is "reserved" -> not valid RAM), or we don't refcount at all.
Yep, that's done. Actually having a BUG_ON PageReserved in the refcount
functions isn't a bad idea for the initial merge, and should help allay
my fears that I might have introduced refcount leaks on PageReserved
pages.
For things like Cell, We'll really end up needing struct page covering
the SPUs for example. That is not valid RAM, shouldn't be refcounted,
but we need to be able to have nopage() returning these etc...
In that case, remap_pfn_range should take care of it for you by
setting the VM_RESERVED flag on the vma.
Swsusp is the main "is valid ram" user I have in mind here. It
wants to know whether or not it should save and restore the
memory of a given `struct page`.
--
SUSE Labs, Novell Inc.
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