[PATCH] mm, hugetlb: Avoid double clearing for hugetlb pages

[Guilherme Piccoli]

When I first wrote that, the design was a bit different, the flag was
called __GFP_HTLB_PAGE or something like that. The design was to
signal/mark the composing pages of hugetlb as exactly this: they are
pages composing a huge page of hugetlb "type". Then, I skipped the
"init_on_alloc" thing for such pages.

If your concern is more about semantics (or giving multiple users,
like drivers, the power to try "optimize" their code and skip this
security feature), I think my first approach was better! This way, the
flag would be restricted to hugetlb usage only.
I've changed my mind about that approach before submitting for 2 reasons:

(a) It feels a waste of resources having a GFP flag *only* to signal
regular pages composing hugetlb pages, it's a single user only,
forever!
(b) Having 2 conditional settings on __GFP_BITS_SHIFT (LOCKDEP and
HUGETLB) started to make this define a bit tricky to code, since we'd
have 2 Kconfig-conditional bits to be set.

So, I've moved to this other approach, hereby submitted.
Cheers,


Guilherme