Root/mm/page_isolation.c

1/*
2 * linux/mm/page_isolation.c
3 */
4
5#include <linux/mm.h>
6#include <linux/page-isolation.h>
7#include <linux/pageblock-flags.h>
8#include <linux/memory.h>
9#include <linux/hugetlb.h>
10#include "internal.h"
11
12int set_migratetype_isolate(struct page *page, bool skip_hwpoisoned_pages)
13{
14    struct zone *zone;
15    unsigned long flags, pfn;
16    struct memory_isolate_notify arg;
17    int notifier_ret;
18    int ret = -EBUSY;
19
20    zone = page_zone(page);
21
22    spin_lock_irqsave(&zone->lock, flags);
23
24    pfn = page_to_pfn(page);
25    arg.start_pfn = pfn;
26    arg.nr_pages = pageblock_nr_pages;
27    arg.pages_found = 0;
28
29    /*
30     * It may be possible to isolate a pageblock even if the
31     * migratetype is not MIGRATE_MOVABLE. The memory isolation
32     * notifier chain is used by balloon drivers to return the
33     * number of pages in a range that are held by the balloon
34     * driver to shrink memory. If all the pages are accounted for
35     * by balloons, are free, or on the LRU, isolation can continue.
36     * Later, for example, when memory hotplug notifier runs, these
37     * pages reported as "can be isolated" should be isolated(freed)
38     * by the balloon driver through the memory notifier chain.
39     */
40    notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
41    notifier_ret = notifier_to_errno(notifier_ret);
42    if (notifier_ret)
43        goto out;
44    /*
45     * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
46     * We just check MOVABLE pages.
47     */
48    if (!has_unmovable_pages(zone, page, arg.pages_found,
49                 skip_hwpoisoned_pages))
50        ret = 0;
51
52    /*
53     * immobile means "not-on-lru" paes. If immobile is larger than
54     * removable-by-driver pages reported by notifier, we'll fail.
55     */
56
57out:
58    if (!ret) {
59        unsigned long nr_pages;
60        int migratetype = get_pageblock_migratetype(page);
61
62        set_pageblock_migratetype(page, MIGRATE_ISOLATE);
63        nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
64
65        __mod_zone_freepage_state(zone, -nr_pages, migratetype);
66    }
67
68    spin_unlock_irqrestore(&zone->lock, flags);
69    if (!ret)
70        drain_all_pages();
71    return ret;
72}
73
74void unset_migratetype_isolate(struct page *page, unsigned migratetype)
75{
76    struct zone *zone;
77    unsigned long flags, nr_pages;
78
79    zone = page_zone(page);
80    spin_lock_irqsave(&zone->lock, flags);
81    if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
82        goto out;
83    nr_pages = move_freepages_block(zone, page, migratetype);
84    __mod_zone_freepage_state(zone, nr_pages, migratetype);
85    set_pageblock_migratetype(page, migratetype);
86out:
87    spin_unlock_irqrestore(&zone->lock, flags);
88}
89
90static inline struct page *
91__first_valid_page(unsigned long pfn, unsigned long nr_pages)
92{
93    int i;
94    for (i = 0; i < nr_pages; i++)
95        if (pfn_valid_within(pfn + i))
96            break;
97    if (unlikely(i == nr_pages))
98        return NULL;
99    return pfn_to_page(pfn + i);
100}
101
102/*
103 * start_isolate_page_range() -- make page-allocation-type of range of pages
104 * to be MIGRATE_ISOLATE.
105 * @start_pfn: The lower PFN of the range to be isolated.
106 * @end_pfn: The upper PFN of the range to be isolated.
107 * @migratetype: migrate type to set in error recovery.
108 *
109 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
110 * the range will never be allocated. Any free pages and pages freed in the
111 * future will not be allocated again.
112 *
113 * start_pfn/end_pfn must be aligned to pageblock_order.
114 * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
115 */
116int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
117                 unsigned migratetype, bool skip_hwpoisoned_pages)
118{
119    unsigned long pfn;
120    unsigned long undo_pfn;
121    struct page *page;
122
123    BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
124    BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
125
126    for (pfn = start_pfn;
127         pfn < end_pfn;
128         pfn += pageblock_nr_pages) {
129        page = __first_valid_page(pfn, pageblock_nr_pages);
130        if (page &&
131            set_migratetype_isolate(page, skip_hwpoisoned_pages)) {
132            undo_pfn = pfn;
133            goto undo;
134        }
135    }
136    return 0;
137undo:
138    for (pfn = start_pfn;
139         pfn < undo_pfn;
140         pfn += pageblock_nr_pages)
141        unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
142
143    return -EBUSY;
144}
145
146/*
147 * Make isolated pages available again.
148 */
149int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
150                unsigned migratetype)
151{
152    unsigned long pfn;
153    struct page *page;
154    BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
155    BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
156    for (pfn = start_pfn;
157         pfn < end_pfn;
158         pfn += pageblock_nr_pages) {
159        page = __first_valid_page(pfn, pageblock_nr_pages);
160        if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
161            continue;
162        unset_migratetype_isolate(page, migratetype);
163    }
164    return 0;
165}
166/*
167 * Test all pages in the range is free(means isolated) or not.
168 * all pages in [start_pfn...end_pfn) must be in the same zone.
169 * zone->lock must be held before call this.
170 *
171 * Returns 1 if all pages in the range are isolated.
172 */
173static int
174__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
175                  bool skip_hwpoisoned_pages)
176{
177    struct page *page;
178
179    while (pfn < end_pfn) {
180        if (!pfn_valid_within(pfn)) {
181            pfn++;
182            continue;
183        }
184        page = pfn_to_page(pfn);
185        if (PageBuddy(page)) {
186            /*
187             * If race between isolatation and allocation happens,
188             * some free pages could be in MIGRATE_MOVABLE list
189             * although pageblock's migratation type of the page
190             * is MIGRATE_ISOLATE. Catch it and move the page into
191             * MIGRATE_ISOLATE list.
192             */
193            if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
194                struct page *end_page;
195
196                end_page = page + (1 << page_order(page)) - 1;
197                move_freepages(page_zone(page), page, end_page,
198                        MIGRATE_ISOLATE);
199            }
200            pfn += 1 << page_order(page);
201        }
202        else if (page_count(page) == 0 &&
203            get_freepage_migratetype(page) == MIGRATE_ISOLATE)
204            pfn += 1;
205        else if (skip_hwpoisoned_pages && PageHWPoison(page)) {
206            /*
207             * The HWPoisoned page may be not in buddy
208             * system, and page_count() is not 0.
209             */
210            pfn++;
211            continue;
212        }
213        else
214            break;
215    }
216    if (pfn < end_pfn)
217        return 0;
218    return 1;
219}
220
221int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
222            bool skip_hwpoisoned_pages)
223{
224    unsigned long pfn, flags;
225    struct page *page;
226    struct zone *zone;
227    int ret;
228
229    /*
230     * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
231     * are not aligned to pageblock_nr_pages.
232     * Then we just check migratetype first.
233     */
234    for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
235        page = __first_valid_page(pfn, pageblock_nr_pages);
236        if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
237            break;
238    }
239    page = __first_valid_page(start_pfn, end_pfn - start_pfn);
240    if ((pfn < end_pfn) || !page)
241        return -EBUSY;
242    /* Check all pages are free or marked as ISOLATED */
243    zone = page_zone(page);
244    spin_lock_irqsave(&zone->lock, flags);
245    ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
246                        skip_hwpoisoned_pages);
247    spin_unlock_irqrestore(&zone->lock, flags);
248    return ret ? 0 : -EBUSY;
249}
250
251struct page *alloc_migrate_target(struct page *page, unsigned long private,
252                  int **resultp)
253{
254    gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
255
256    /*
257     * TODO: allocate a destination hugepage from a nearest neighbor node,
258     * accordance with memory policy of the user process if possible. For
259     * now as a simple work-around, we use the next node for destination.
260     */
261    if (PageHuge(page)) {
262        nodemask_t src = nodemask_of_node(page_to_nid(page));
263        nodemask_t dst;
264        nodes_complement(dst, src);
265        return alloc_huge_page_node(page_hstate(compound_head(page)),
266                        next_node(page_to_nid(page), dst));
267    }
268
269    if (PageHighMem(page))
270        gfp_mask |= __GFP_HIGHMEM;
271
272    return alloc_page(gfp_mask);
273}
274

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