On Tue, 25 May 2021 08:40:10 PDT (-0700), rdunlap@xxxxxxxxxxxxx wrote:
On 5/25/21 3:33 AM, Mike Rapoport wrote:
On Mon, May 24, 2021 at 05:13:02PM -0700, Randy Dunlap wrote:
Fix a Kconfig warning and many build errors:
WARNING: unmet direct dependencies detected for COMPACTION
Depends on [n]: MMU [=n]
Selected by [y]:
- TRANSPARENT_HUGEPAGE [=y] && HAVE_ARCH_TRANSPARENT_HUGEPAGE [=y]
and the subseqent thousands of build errors and warnings.
Fixes: e88b333142e4 ("riscv: mm: add THP support on 64-bit")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Nanyong Sun <sunnanyong@xxxxxxxxxx>
Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
---
I really think that mm/Kconfig should have "depends on MMU" for
TRANSPARENT_HUGEPAGE, but commit 15626062f4a9 from 2012
("thp, x86: introduce HAVE_ARCH_TRANSPARENT_HUGEPAGE") thought
differently. I.e., mm/Kconfig should be protecting all arches
against this Kconfig problem.
We could
diff --git a/mm/Kconfig b/mm/Kconfig
index 02d44e3420f5..85bc8bf32e7b 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -403,7 +403,7 @@ config NOMMU_INITIAL_TRIM_EXCESS
config TRANSPARENT_HUGEPAGE
bool "Transparent Hugepage Support"
- depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
+ depends on MMU && HAVE_ARCH_TRANSPARENT_HUGEPAGE
select COMPACTION
select XARRAY_MULTI
help
but in a sense HAVE_ARCH_TRANSPARENT_HUGEPAGE should imply that MMU is
selected :)
Yes, I had this patch before the one that I sent but decided against it
based on history.
IMO 15626062f4a9 ("thp, x86: introduce HAVE_ARCH_TRANSPARENT_HUGEPAGE")
is really saying "the arches that have transparent huge pages are MMU=y,
so we don't need the extra check". That seems reasonable as of when the
code landed, and while arm has MMU=n and THP it already depends on MMU
(via ARM_LPAE, which seems kind of natural there).
The generic version seems fine to me, but I'm going to take this one now
so we can avoid the build issues.
arch/riscv/Kconfig | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- linux-next-20210524.orig/arch/riscv/Kconfig
+++ linux-next-20210524/arch/riscv/Kconfig
@@ -106,7 +106,7 @@ config RISCV
select SYSCTL_EXCEPTION_TRACE
select THREAD_INFO_IN_TASK
select UACCESS_MEMCPY if !MMU
- select HAVE_ARCH_TRANSPARENT_HUGEPAGE if 64BIT
+ select HAVE_ARCH_TRANSPARENT_HUGEPAGE if 64BIT && MMU
config ARCH_MMAP_RND_BITS_MIN
default 18 if 64BIT
thanks.
