On Fri, Nov 29, 2013 at 12:29:13AM +0800, Jianyu Zhan wrote:
> Currently we are implementing vmalloc_to_pfn() as a wrapper of
> vmalloc_to_page(), which is implemented as follow:
>
> 1. walks the page talbes to generates the corresponding pfn,
> 2. then wraps the pfn to struct page,
> 3. returns it.
>
> And vmalloc_to_pfn() re-wraps the vmalloc_to_page() to get the pfn.
>
> This seems too circuitous, so this patch reverses the way:
> implementing the vmalloc_to_page() as a wrapper of vmalloc_to_pfn().
> This makes vmalloc_to_pfn() and vmalloc_to_page() slightly effective.
Any numbers for efficiency?
>
> No functional change.
>
> Signed-off-by: Jianyu Zhan <nasa4836@xxxxxxxxx>
> ---
> mm/vmalloc.c | 20 ++++++++++----------
> 1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 0fdf968..a335e21 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -220,12 +220,12 @@ int is_vmalloc_or_module_addr(const void *x)
> }
>
> /*
> - * Walk a vmap address to the struct page it maps.
> + * Walk a vmap address to the physical pfn it maps to.
> */
> -struct page *vmalloc_to_page(const void *vmalloc_addr)
> +unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
> {
> unsigned long addr = (unsigned long) vmalloc_addr;
> - struct page *page = NULL;
> + unsigned long pfn;
uninitialized pfn will lead to a bug.
> pgd_t *pgd = pgd_offset_k(addr);
>
> /*
> @@ -244,23 +244,23 @@ struct page *vmalloc_to_page(const void *vmalloc_addr)
> ptep = pte_offset_map(pmd, addr);
> pte = *ptep;
> if (pte_present(pte))
> - page = pte_page(pte);
> + pfn = pte_page(pte);
page_to_pfn is missed here.
Have you ever tested there is no functional changes?
Vladimir
> pte_unmap(ptep);
> }
> }
> }
> - return page;
> + return pfn;
> }
> -EXPORT_SYMBOL(vmalloc_to_page);
> +EXPORT_SYMBOL(vmalloc_to_pfn);
>
> /*
> - * Map a vmalloc()-space virtual address to the physical page frame number.
> + * Map a vmalloc()-space virtual address to the struct page.
> */
> -unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
> +struct page *vmalloc_to_page(const void *vmalloc_addr)
> {
> - return page_to_pfn(vmalloc_to_page(vmalloc_addr));
> + return pfn_to_page(vmalloc_to_pfn(vmalloc_addr));
> }
> -EXPORT_SYMBOL(vmalloc_to_pfn);
> +EXPORT_SYMBOL(vmalloc_to_page);
>
>
> /*** Global kva allocator ***/
>
> --
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