[PATCH 2/2] arm64: mm: run pgtable_page_ctor() on non-swapper translation table pages

[Catalin Marinas]

On Mon, Jul 25, 2016 at 03:43:21PM +0100, Suzuki K. Poulose wrote:
> On 25/07/16 15:31, Suzuki K Poulose wrote:
> >On 22/07/16 18:32, Ard Biesheuvel wrote:
> >>The kernel page table creation routines are accessible to other subsystems
> >>(e.g., EFI) via the create_pgd_mapping() entry point, which allows mappings
> >>to be created that are not covered by init_mm.
> >>
> >>Since generic code such as apply_to_page_range() may expect translation
> >>table pages that are not associated with init_mm to be covered by fully
> >>constructed struct pages, add a call to pgtable_page_ctor() in the alloc
> >>function used by create_pgd_mapping. Since it is no longer used by
> >>create_mapping_late(), also update the name of this function to better
> >>reflect its purpose.
> >>
> >>Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> >>---
> >> arch/arm64/mm/mmu.c | 9 ++++++---
> >> 1 file changed, 6 insertions(+), 3 deletions(-)
> >>
> >>diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> >>index 33f36cede02d..51a558195bb9 100644
> >>--- a/arch/arm64/mm/mmu.c
> >>+++ b/arch/arm64/mm/mmu.c
> >>@@ -268,10 +268,11 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
> >>     } while (pgd++, addr = next, addr != end);
> >> }
> >>
> >>-static phys_addr_t late_pgtable_alloc(void)
> >>+static phys_addr_t pgd_pgtable_alloc(void)
> >> {
> >>     void *ptr = (void *)__get_free_page(PGALLOC_GFP);
> >>-    BUG_ON(!ptr);
> >>+    if (!ptr || !pgtable_page_ctor(virt_to_page(ptr)))
> >
> >Should we free the page and return NULL when we encounter an error
> >in pgtable_page_ctor(), like the rest of the callers ?
> >
> >
> >>+        BUG();
> 
> Just to clarify, of course with the BUG() retained.

But then, if we return, we no longer trigger BUG(). The callers of this
function assume that it always succeeds or does not return.

-- 
Catalin