page_alloc: use vmalloc_huge for large system hash

page_alloc: use vmalloc_huge for large system hash

Use vmalloc_huge() in alloc_large_system_hash() so that large system
hash (>= PMD_SIZE) could benefit from huge pages.

Note that vmalloc_huge only allocates huge pages for systems with
HAVE_ARCH_HUGE_VMALLOC.

Signed-off-by: Song Liu <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Rik van Riel <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>