Currently without THP being enabled, MAX_ORDER via FORCE_MAX_ZONEORDER gets
reduced to 11, which falls below HUGETLB_PAGE_ORDER for certain 16K and 64K
page size configurations. This is problematic which throws up the following
warning during boot as pageblock_order via HUGETLB_PAGE_ORDER order exceeds
MAX_ORDER.

WARNING: CPU: 7 PID: 127 at mm/vmstat.c:1092 __fragmentation_index+0x58/0x70
Modules linked in:
CPU: 7 PID: 127 Comm: kswapd0 Not tainted 5.12.0-rc1-00005-g0221e3101a1 #237
Hardware name: linux,dummy-virt (DT)
pstate: 20400005 (nzCv daif +PAN -UAO -TCO BTYPE=--)
pc : __fragmentation_index+0x58/0x70
lr : fragmentation_index+0x88/0xa8
sp : ffff800016ccfc00
x29: ffff800016ccfc00 x28: 0000000000000000
x27: ffff800011fd4000 x26: 0000000000000002
x25: ffff800016ccfda0 x24: 0000000000000002
x23: 0000000000000640 x22: ffff0005ffcb5b18
x21: 0000000000000002 x20: 000000000000000d
x19: ffff0005ffcb3980 x18: 0000000000000004
x17: 0000000000000001 x16: 0000000000000019
x15: ffff800011ca7fb8 x14: 00000000000002b3
x13: 0000000000000000 x12: 00000000000005e0
x11: 0000000000000003 x10: 0000000000000080
x9 : ffff800011c93948 x8 : 0000000000000000
x7 : 0000000000000000 x6 : 0000000000007000
x5 : 0000000000007944 x4 : 0000000000000032
x3 : 000000000000001c x2 : 000000000000000b
x1 : ffff800016ccfc10 x0 : 000000000000000d
Call trace:
__fragmentation_index+0x58/0x70
compaction_suitable+0x58/0x78
wakeup_kcompactd+0x8c/0xd8
balance_pgdat+0x570/0x5d0
kswapd+0x1e0/0x388
kthread+0x154/0x158
ret_from_fork+0x10/0x30

This solves the problem via keeping FORCE_MAX_ZONEORDER unchanged with or
without THP on 16K and 64K page size configurations, making sure that the
HUGETLB_PAGE_ORDER (and pageblock_order) would never exceed MAX_ORDER.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/1614597914-28565-1-git-send-email-anshuman.khandual@arm.comSigned-off-by: Will Deacon <will@kernel.org>