arch/arm/mm/flush.c

   1 /*
   2  *  linux/arch/arm/mm/flush.c
   3  *
   4  *  Copyright (C) 1995-2002 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/module.h>
  11 #include <linux/mm.h>
  12 #include <linux/pagemap.h>
  13
  14 #include <asm/cacheflush.h>
  15 #include <asm/system.h>
  16
  17 static void __flush_dcache_page(struct address_space *mapping, struct page *page)
  18 {
  19         struct mm_struct *mm = current->active_mm;
  20         struct vm_area_struct *mpnt;
  21         struct prio_tree_iter iter;
  22         pgoff_t pgoff;
  23
  24         /*
  25          * Writeback any data associated with the kernel mapping of this
  26          * page.  This ensures that data in the physical page is mutually
  27          * coherent with the kernels mapping.
  28          */
  29         __cpuc_flush_dcache_page(page_address(page));
  30
  31         /*
  32          * If there's no mapping pointer here, then this page isn't
  33          * visible to userspace yet, so there are no cache lines
  34          * associated with any other aliases.
  35          */
  36         if (!mapping)
  37                 return;
  38
  39         /*
  40          * There are possible user space mappings of this page:
  41          * - VIVT cache: we need to also write back and invalidate all user
  42          *   data in the current VM view associated with this page.
  43          * - aliasing VIPT: we only need to find one mapping of this page.
  44          */
  45         pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
  46
  47         flush_dcache_mmap_lock(mapping);
  48         vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
  49                 unsigned long offset;
  50
  51                 /*
  52                  * If this VMA is not in our MM, we can ignore it.
  53                  */
  54                 if (mpnt->vm_mm != mm)
  55                         continue;
  56                 if (!(mpnt->vm_flags & VM_MAYSHARE))
  57                         continue;
  58                 offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
  59                 flush_cache_page(mpnt, mpnt->vm_start + offset, page_to_pfn(page));
  60                 if (cache_is_vipt())
  61                         break;
  62         }
  63         flush_dcache_mmap_unlock(mapping);
  64 }
  65
  66 /*
  67  * Ensure cache coherency between kernel mapping and userspace mapping
  68  * of this page.
  69  *
  70  * We have three cases to consider:
  71  *  - VIPT non-aliasing cache: fully coherent so nothing required.
  72  *  - VIVT: fully aliasing, so we need to handle every alias in our
  73  *          current VM view.
  74  *  - VIPT aliasing: need to handle one alias in our current VM view.
  75  *
  76  * If we need to handle aliasing:
  77  *  If the page only exists in the page cache and there are no user
  78  *  space mappings, we can be lazy and remember that we may have dirty
  79  *  kernel cache lines for later.  Otherwise, we assume we have
  80  *  aliasing mappings.
  81  */
  82 void flush_dcache_page(struct page *page)
  83 {
  84         struct address_space *mapping = page_mapping(page);
  85
  86         if (cache_is_vipt_nonaliasing())
  87                 return;
  88
  89         if (mapping && !mapping_mapped(mapping))
  90                 set_bit(PG_dcache_dirty, &page->flags);
  91         else
  92                 __flush_dcache_page(mapping, page);
  93 }
  94 EXPORT_SYMBOL(flush_dcache_page);