Re: [RFC][PATCH 1/4] arm64: Drop alloc function from create_mapping

[Laura Abbott]

On 01/26/2016 03:22 AM, Mark Rutland wrote:
> On Mon, Jan 25, 2016 at 08:52:12AM -0800, Laura Abbott wrote:
> > create_mapping is only used in fixmap_remap_fdt. All the create_mapping
> > calls need to happen on existing translation table pages without
> > additional allocations. Rather than have an alloc function be called
> > and fail, just set it to NULL and catch it's use.
>
> This looks sensible to me, though I think we should rename
> create_mapping to something that makes it clear that not allocating
> pages is a deliberate design decision, and thus it must be called with
> care.
>
> Perhaps create_mapping_noalloc?

I was wondering about that. That name sounds clearer.

> Thanks,
> Mark.
>
> > Signed-off-by: Laura Abbott <labbott@xxxxxxxxxxxxxxxxx>
> > ---
> >   arch/arm64/mm/mmu.c | 14 ++++++++++----
> >   1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index e141762..2d6e7cf 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -116,7 +116,9 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
> >   	pte_t *pte;
> >
> >   	if (pmd_none(*pmd) || pmd_sect(*pmd)) {
> > -		phys_addr_t pte_phys = pgtable_alloc();
> > +		phys_addr_t pte_phys;
> > +		BUG_ON(!pgtable_alloc);
> > +		pte_phys = pgtable_alloc();
> >   		pte = pte_fixmap(pte_phys);
> >   		if (pmd_sect(*pmd))
> >   			split_pmd(pmd, pte);
> > @@ -158,7 +160,9 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
> >   	 * Check for initial section mappings in the pgd/pud and remove them.
> >   	 */
> >   	if (pud_none(*pud) || pud_sect(*pud)) {
> > -		phys_addr_t pmd_phys = pgtable_alloc();
> > +		phys_addr_t pmd_phys;
> > +		BUG_ON(!pgtable_alloc);
> > +		pmd_phys = pgtable_alloc();
> >   		pmd = pmd_fixmap(pmd_phys);
> >   		if (pud_sect(*pud)) {
> >   			/*
> > @@ -223,7 +227,9 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
> >   	unsigned long next;
> >
> >   	if (pgd_none(*pgd)) {
> > -		phys_addr_t pud_phys = pgtable_alloc();
> > +		phys_addr_t pud_phys;
> > +		BUG_ON(!pgtable_alloc);
> > +		pud_phys = pgtable_alloc();
> >   		__pgd_populate(pgd, pud_phys, PUD_TYPE_TABLE);
> >   	}
> >   	BUG_ON(pgd_bad(*pgd));
> > @@ -319,7 +325,7 @@ static void __init create_mapping(phys_addr_t phys, unsigned long virt,
> >   		return;
> >   	}
> >   	__create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
> > -			     early_pgtable_alloc);
> > +			     NULL);
> >   }
> >
> >   void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
> > --
> > 2.5.0