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Date: Fri, 14 Nov 2008 13:19:56 +1100
From: Nick Piggin <nickpiggin@...oo.com.au>
To: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Linux Memory Management List <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Subject: Re: [PATCH 1/2] mm: implement remap_pfn_range with apply_to_page_range
On Friday 14 November 2008 04:19, Jeremy Fitzhardinge wrote:
> remap_pte_range() just wants to apply a function over a range of ptes
> corresponding to a virtual address range. That's exactly what
> apply_to_page_range() does, so use it.
This isn't performance critical to anyone?
I see DRM, IB, GRU, other media and video drivers use it.
It IS exactly what apply_to_page_range does, I grant you. But so does
our traditional set of nested loops. So is there any particular reason
to change it? You're not planning to change fork/exit next, are you? :)
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> ---
> mm/memory.c | 92
> ++++++++++++----------------------------------------------- 1 file changed,
> 20 insertions(+), 72 deletions(-)
>
> ===================================================================
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1472,69 +1472,20 @@
> }
> EXPORT_SYMBOL(vm_insert_mixed);
>
> -/*
> - * maps a range of physical memory into the requested pages. the old
> - * mappings are removed. any references to nonexistent pages results
> - * in null mappings (currently treated as "copy-on-access")
> - */
> -static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
> - unsigned long addr, unsigned long end,
> - unsigned long pfn, pgprot_t prot)
> +struct remap_data {
> + struct mm_struct *mm;
> + unsigned long pfn;
> + pgprot_t prot;
> +};
> +
> +static int remap_area_pte_fn(pte_t *ptep, pgtable_t token,
> + unsigned long addr, void *data)
> {
> - pte_t *pte;
> - spinlock_t *ptl;
> + struct remap_data *rmd = data;
> + pte_t pte = pte_mkspecial(pfn_pte(rmd->pfn++, rmd->prot));
>
> - pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
> - if (!pte)
> - return -ENOMEM;
> - arch_enter_lazy_mmu_mode();
> - do {
> - BUG_ON(!pte_none(*pte));
> - set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
> - pfn++;
> - } while (pte++, addr += PAGE_SIZE, addr != end);
> - arch_leave_lazy_mmu_mode();
> - pte_unmap_unlock(pte - 1, ptl);
> - return 0;
> -}
> + set_pte_at(rmd->mm, addr, ptep, pte);
>
> -static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
> - unsigned long addr, unsigned long end,
> - unsigned long pfn, pgprot_t prot)
> -{
> - pmd_t *pmd;
> - unsigned long next;
> -
> - pfn -= addr >> PAGE_SHIFT;
> - pmd = pmd_alloc(mm, pud, addr);
> - if (!pmd)
> - return -ENOMEM;
> - do {
> - next = pmd_addr_end(addr, end);
> - if (remap_pte_range(mm, pmd, addr, next,
> - pfn + (addr >> PAGE_SHIFT), prot))
> - return -ENOMEM;
> - } while (pmd++, addr = next, addr != end);
> - return 0;
> -}
> -
> -static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
> - unsigned long addr, unsigned long end,
> - unsigned long pfn, pgprot_t prot)
> -{
> - pud_t *pud;
> - unsigned long next;
> -
> - pfn -= addr >> PAGE_SHIFT;
> - pud = pud_alloc(mm, pgd, addr);
> - if (!pud)
> - return -ENOMEM;
> - do {
> - next = pud_addr_end(addr, end);
> - if (remap_pmd_range(mm, pud, addr, next,
> - pfn + (addr >> PAGE_SHIFT), prot))
> - return -ENOMEM;
> - } while (pud++, addr = next, addr != end);
> return 0;
> }
>
> @@ -1551,10 +1502,9 @@
> int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
> unsigned long pfn, unsigned long size, pgprot_t prot)
> {
> - pgd_t *pgd;
> - unsigned long next;
> unsigned long end = addr + PAGE_ALIGN(size);
> struct mm_struct *mm = vma->vm_mm;
> + struct remap_data rmd;
> int err;
>
> /*
> @@ -1584,16 +1534,14 @@
> vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
>
> BUG_ON(addr >= end);
> - pfn -= addr >> PAGE_SHIFT;
> - pgd = pgd_offset(mm, addr);
> - flush_cache_range(vma, addr, end);
> - do {
> - next = pgd_addr_end(addr, end);
> - err = remap_pud_range(mm, pgd, addr, next,
> - pfn + (addr >> PAGE_SHIFT), prot);
> - if (err)
> - break;
> - } while (pgd++, addr = next, addr != end);
> +
> + rmd.mm = mm;
> + rmd.pfn = pfn;
> + rmd.prot = prot;
> +
> + err = apply_to_page_range(mm, addr, end - addr,
> + remap_area_pte_fn, &rmd);
> +
> return err;
> }
> EXPORT_SYMBOL(remap_pfn_range);
--
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