Re: [PATCH mm-unstable] mm: make SPARSEMEM_VMEMMAP_PREINIT an internal option

[Frank van der Linden <fvdl@google.com>]

On Thu, Feb 27, 2025 at 10:57 AM Frank van der Linden <fvdl@google.com> wrote:
>
> SPARSEMEM_VMEMMAP_PREINIT is not useful as a user-facing
> option, it is just something that should be selected
> if a subsystem wishes to do vmemmap preinit. That's
> currently only HUGETLB_PAGE_OPTIMIZE_VMEMMAP.
>
> So, make it a default-less option that is only selected
> by HUGETLB_PAGE_OPTIMIZE_VMEMMAP, iff the architecture
> has noted it is capable of doing hugetlb vmemmap preinit.
> That is done via ARCH_WANT_HUGETLB_VMEMMAP_PREINIT,
> renamed from ARCH_WANT_SPARSE_VMEMMAP_PREINIT.
>
> Fixes: a916062fdd134 ("mm/sparse: allow for alternate vmemmap section init at boot")
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Frank van der Linden <fvdl@google.com>
> ---
>  arch/x86/Kconfig | 2 +-
>  fs/Kconfig       | 1 +
>  mm/Kconfig       | 9 ++++-----
>  3 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 541347a6fa81..d05f26e301a9 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -147,7 +147,7 @@ config X86
>         select ARCH_WANT_LD_ORPHAN_WARN
>         select ARCH_WANT_OPTIMIZE_DAX_VMEMMAP   if X86_64
>         select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP       if X86_64
> -       select ARCH_WANT_SPARSEMEM_VMEMMAP_PREINIT if X86_64
> +       select ARCH_WANT_HUGETLB_VMEMMAP_PREINIT if X86_64
>         select ARCH_WANTS_THP_SWAP              if X86_64
>         select ARCH_HAS_PARANOID_L1D_FLUSH
>         select BUILDTIME_TABLE_SORT
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 64d420e3c475..8bcd3a6f80ab 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -286,6 +286,7 @@ config HUGETLB_PAGE_OPTIMIZE_VMEMMAP
>         def_bool HUGETLB_PAGE
>         depends on ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
>         depends on SPARSEMEM_VMEMMAP
> +       select SPARSEMEM_VMEMMAP_PREINIT if ARCH_WANT_HUGETLB_VMEMMAP_PREINIT
>
>  config HUGETLB_PMD_PAGE_TABLE_SHARING
>         def_bool HUGETLB_PAGE
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 2761098dbc1a..7262a145ed64 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -443,13 +443,9 @@ config SPARSEMEM_VMEMMAP
>           pfn_to_page and page_to_pfn operations.  This is the most
>           efficient option when sufficient kernel resources are available.
>
> -config ARCH_WANT_SPARSEMEM_VMEMMAP_PREINIT
> +config SPARSEMEM_VMEMMAP_PREINIT
>         bool
>
> -config SPARSEMEM_VMEMMAP_PREINIT
> -       bool "Early init of sparse memory virtual memmap"
> -       depends on SPARSEMEM_VMEMMAP && ARCH_WANT_SPARSEMEM_VMEMMAP_PREINIT
> -       default y
>  #
>  # Select this config option from the architecture Kconfig, if it is preferred
>  # to enable the feature of HugeTLB/dev_dax vmemmap optimization.
> @@ -460,6 +456,9 @@ config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
>  config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
>         bool
>
> +config ARCH_WANT_HUGETLB_VMEMMAP_PREINIT
> +       bool
> +
>  config HAVE_MEMBLOCK_PHYS_MAP
>         bool
>
> --
> 2.48.1.711.g2feabab25a-goog
>

Hm, this should actually be split in two patches, since the x86 change
comes in a later patch in the original series.

Let me resend this in a v2 that contains two separate patches.

Sorry about the noise.

- Frank