Re: [PATCH v3 06/14] mm/sparse-vmemmap: refactor core of vmemmap_populate_basepages() to helper

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On Wed, Jul 14, 2021 at 12:36 PM Joao Martins <joao.m.martins@xxxxxxxxxx> wrote:
>
> In preparation for describing a memmap with compound pages, move the
> actual pte population logic into a separate function
> vmemmap_populate_address() and have vmemmap_populate_basepages() walk
> through all base pages it needs to populate.
>
> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> ---
>  mm/sparse-vmemmap.c | 44 ++++++++++++++++++++++++++------------------
>  1 file changed, 26 insertions(+), 18 deletions(-)
>
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 80d3ba30d345..76f4158f6301 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -570,33 +570,41 @@ pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
>         return pgd;
>  }
>
> -int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
> -                                        int node, struct vmem_altmap *altmap)
> +static int __meminit vmemmap_populate_address(unsigned long addr, int node,
> +                                             struct vmem_altmap *altmap)
>  {
> -       unsigned long addr = start;
>         pgd_t *pgd;
>         p4d_t *p4d;
>         pud_t *pud;
>         pmd_t *pmd;
>         pte_t *pte;
>
> +       pgd = vmemmap_pgd_populate(addr, node);
> +       if (!pgd)
> +               return -ENOMEM;
> +       p4d = vmemmap_p4d_populate(pgd, addr, node);
> +       if (!p4d)
> +               return -ENOMEM;
> +       pud = vmemmap_pud_populate(p4d, addr, node);
> +       if (!pud)
> +               return -ENOMEM;
> +       pmd = vmemmap_pmd_populate(pud, addr, node);
> +       if (!pmd)
> +               return -ENOMEM;
> +       pte = vmemmap_pte_populate(pmd, addr, node, altmap);
> +       if (!pte)
> +               return -ENOMEM;
> +       vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);

Missing a return here:

mm/sparse-vmemmap.c:598:1: error: control reaches end of non-void
function [-Werror=return-type]

Yes, it's fixed up in a later patch, but might as well not leave the
bisect breakage lying around, and the kbuild robot would gripe about
this eventually as well.


> +}
> +
> +int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
> +                                        int node, struct vmem_altmap *altmap)
> +{
> +       unsigned long addr = start;
> +
>         for (; addr < end; addr += PAGE_SIZE) {
> -               pgd = vmemmap_pgd_populate(addr, node);
> -               if (!pgd)
> -                       return -ENOMEM;
> -               p4d = vmemmap_p4d_populate(pgd, addr, node);
> -               if (!p4d)
> -                       return -ENOMEM;
> -               pud = vmemmap_pud_populate(p4d, addr, node);
> -               if (!pud)
> -                       return -ENOMEM;
> -               pmd = vmemmap_pmd_populate(pud, addr, node);
> -               if (!pmd)
> -                       return -ENOMEM;
> -               pte = vmemmap_pte_populate(pmd, addr, node, altmap);
> -               if (!pte)
> +               if (vmemmap_populate_address(addr, node, altmap))
>                         return -ENOMEM;

I'd prefer:

rc = vmemmap_populate_address(addr, node, altmap);
if (rc)
    return rc;

...in case future refactoring adds different error codes to pass up.


> -               vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);
>         }
>
>         return 0;
> --
> 2.17.1
>



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