mm: avoid zeroing user movable page twice with init_on_alloc=1

Commit 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and
init_on_free=1 boot options") forces allocated page to be zeroed in
post_alloc_hook() when init_on_alloc=1.

For order-0 folios, if arch does not define
vma_alloc_zeroed_movable_folio(), the default implementation again zeros
the page return from the buddy allocator.  So the page is zeroed twice. 
Fix it by passing __GFP_ZERO instead to avoid double page zeroing.  At the
moment, s390,arm64,x86,alpha,m68k are not impacted since they define their
own vma_alloc_zeroed_movable_folio().

For >0 order folios (mTHP and PMD THP), folio_zero_user() is called to
zero the folio again.  Fix it by calling folio_zero_user() only if
init_on_alloc is set.  All arch are impacted.

Add alloc_zeroed() helper to encapsulate the init_on_alloc check.

[[email protected]: comment fixes, per David]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Zi Yan <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Kefeng Wang <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Miaohe Lin <[email protected]>
Cc: Ryan Roberts <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions