/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
17static 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 */
82void 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}
94EXPORT_SYMBOL(flush_dcache_page);