[PATCH V3] riscv: mm: hugetlb: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

[guoren at kernel.org]

From: Guo Ren <guoren at linux.alibaba.com>

Add HVO support for RISC-V; see commit 6be24bed9da3 ("mm: hugetlb:
introduce a new config HUGETLB_PAGE_FREE_VMEMMAP"). This patch is
similar to commit 1e63ac088f20 ("arm64: mm: hugetlb: enable
HUGETLB_PAGE_FREE_VMEMMAP for arm64"), and riscv's motivation is the
same as arm64. The current riscv was ready to enable HVO after fixup,
ref commit d33deda095d3 ("riscv/mm: hugepage's PG_dcache_clean flag
is only set in head page").

See Documentation/mm/vmemmap_dedup.rst for more details.

The HugeTLB VmemmapvOptimization (HVO) defaults to off in Kconfig.

Here is the riscv test log:
cat /proc/sys/vm/hugetlb_optimize_vmemmap
echo 8 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
mount -t hugetlbfs none test/ -o pagesize=2048k
<Try some simple hugetlb test in test dir, no problem found.>

Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Signed-off-by: Guo Ren <guoren at kernel.org>
Link: https://lore.kernel.org/linux-riscv/1F5AF29D-708A-483B-A29F-CAEE6F554866@linux.dev/
Acked-by: Muchun Song <songmuchun at bytedance.com>
Reviewed-by: Andrew Jones <ajones at ventanamicro.com>
---
Changelog:
V3:
 - Optimize the commit log (Thx Andrew)
 - Optimize alphabet order (Thx Conor)
 - Add Reviewed-by tag

V2:
 - Optimize the commit log
 - Remove riscv page compound_head fixup which has been merged.
 - Rebase on riscv for-next (20230127)
 - Add HVO author's acked-by

V1:
https://lore.kernel.org/linux-riscv/20221023133205.3493564-1-guoren@kernel.org/
---
 arch/riscv/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index e2b656043abf..54972e719f49 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -45,6 +45,7 @@ config RISCV
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_GENERAL_HUGETLB
+	select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
 	select ARCH_WANTS_THP_SWAP if HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
-- 
2.36.1