page_alloc.c (b5810039a54e5babf428e9a1e89fc1940fabff11) page_alloc.c (4c21e2f2441dc5fbb957b030333f5a3f2d02dea7)
1/*
2 * linux/mm/page_alloc.c
3 *
4 * Manages the free list, the system allocates free pages here.
5 * Note that kmalloc() lives in slab.c
6 *
7 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 * Swap reorganised 29.12.95, Stephen Tweedie

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149 int nr_pages = 1 << order;
150
151 page[1].mapping = NULL;
152 page[1].index = order;
153 for (i = 0; i < nr_pages; i++) {
154 struct page *p = page + i;
155
156 SetPageCompound(p);
1/*
2 * linux/mm/page_alloc.c
3 *
4 * Manages the free list, the system allocates free pages here.
5 * Note that kmalloc() lives in slab.c
6 *
7 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 * Swap reorganised 29.12.95, Stephen Tweedie

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149 int nr_pages = 1 << order;
150
151 page[1].mapping = NULL;
152 page[1].index = order;
153 for (i = 0; i < nr_pages; i++) {
154 struct page *p = page + i;
155
156 SetPageCompound(p);
157 p->private = (unsigned long)page;
157 set_page_private(p, (unsigned long)page);
158 }
159}
160
161static void destroy_compound_page(struct page *page, unsigned long order)
162{
163 int i;
164 int nr_pages = 1 << order;
165
166 if (!PageCompound(page))
167 return;
168
169 if (page[1].index != order)
170 bad_page(__FUNCTION__, page);
171
172 for (i = 0; i < nr_pages; i++) {
173 struct page *p = page + i;
174
175 if (!PageCompound(p))
176 bad_page(__FUNCTION__, page);
158 }
159}
160
161static void destroy_compound_page(struct page *page, unsigned long order)
162{
163 int i;
164 int nr_pages = 1 << order;
165
166 if (!PageCompound(page))
167 return;
168
169 if (page[1].index != order)
170 bad_page(__FUNCTION__, page);
171
172 for (i = 0; i < nr_pages; i++) {
173 struct page *p = page + i;
174
175 if (!PageCompound(p))
176 bad_page(__FUNCTION__, page);
177 if (p->private != (unsigned long)page)
177 if (page_private(p) != (unsigned long)page)
178 bad_page(__FUNCTION__, page);
179 ClearPageCompound(p);
180 }
181}
182#endif /* CONFIG_HUGETLB_PAGE */
183
184/*
185 * function for dealing with page's order in buddy system.
186 * zone->lock is already acquired when we use these.
187 * So, we don't need atomic page->flags operations here.
188 */
189static inline unsigned long page_order(struct page *page) {
178 bad_page(__FUNCTION__, page);
179 ClearPageCompound(p);
180 }
181}
182#endif /* CONFIG_HUGETLB_PAGE */
183
184/*
185 * function for dealing with page's order in buddy system.
186 * zone->lock is already acquired when we use these.
187 * So, we don't need atomic page->flags operations here.
188 */
189static inline unsigned long page_order(struct page *page) {
190 return page->private;
190 return page_private(page);
191}
192
193static inline void set_page_order(struct page *page, int order) {
191}
192
193static inline void set_page_order(struct page *page, int order) {
194 page->private = order;
194 set_page_private(page, order);
195 __SetPagePrivate(page);
196}
197
198static inline void rmv_page_order(struct page *page)
199{
200 __ClearPagePrivate(page);
195 __SetPagePrivate(page);
196}
197
198static inline void rmv_page_order(struct page *page)
199{
200 __ClearPagePrivate(page);
201 page->private = 0;
201 set_page_private(page, 0);
202}
203
204/*
205 * Locate the struct page for both the matching buddy in our
206 * pair (buddy1) and the combined O(n+1) page they form (page).
207 *
208 * 1) Any buddy B1 will have an order O twin B2 which satisfies
209 * the following equation:

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233}
234
235/*
236 * This function checks whether a page is free && is the buddy
237 * we can do coalesce a page and its buddy if
238 * (a) the buddy is free &&
239 * (b) the buddy is on the buddy system &&
240 * (c) a page and its buddy have the same order.
202}
203
204/*
205 * Locate the struct page for both the matching buddy in our
206 * pair (buddy1) and the combined O(n+1) page they form (page).
207 *
208 * 1) Any buddy B1 will have an order O twin B2 which satisfies
209 * the following equation:

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233}
234
235/*
236 * This function checks whether a page is free && is the buddy
237 * we can do coalesce a page and its buddy if
238 * (a) the buddy is free &&
239 * (b) the buddy is on the buddy system &&
240 * (c) a page and its buddy have the same order.
241 * for recording page's order, we use page->private and PG_private.
241 * for recording page's order, we use page_private(page) and PG_private.
242 *
243 */
244static inline int page_is_buddy(struct page *page, int order)
245{
246 if (PagePrivate(page) &&
247 (page_order(page) == order) &&
248 page_count(page) == 0)
249 return 1;

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259 * units of memory (here, pages), and each level above it describes
260 * pairs of units from the levels below, hence, "buddies".
261 * At a high level, all that happens here is marking the table entry
262 * at the bottom level available, and propagating the changes upward
263 * as necessary, plus some accounting needed to play nicely with other
264 * parts of the VM system.
265 * At each level, we keep a list of pages, which are heads of continuous
266 * free pages of length of (1 << order) and marked with PG_Private.Page's
242 *
243 */
244static inline int page_is_buddy(struct page *page, int order)
245{
246 if (PagePrivate(page) &&
247 (page_order(page) == order) &&
248 page_count(page) == 0)
249 return 1;

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259 * units of memory (here, pages), and each level above it describes
260 * pairs of units from the levels below, hence, "buddies".
261 * At a high level, all that happens here is marking the table entry
262 * at the bottom level available, and propagating the changes upward
263 * as necessary, plus some accounting needed to play nicely with other
264 * parts of the VM system.
265 * At each level, we keep a list of pages, which are heads of continuous
266 * free pages of length of (1 << order) and marked with PG_Private.Page's
267 * order is recorded in page->private field.
267 * order is recorded in page_private(page) field.
268 * So when we are allocating or freeing one, we can derive the state of the
269 * other. That is, if we allocate a small block, and both were
270 * free, the remainder of the region must be split into blocks.
271 * If a block is freed, and its buddy is also free, then this
272 * triggers coalescing into a block of larger size.
273 *
274 * -- wli
275 */

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458 1 << PG_swapcache |
459 1 << PG_writeback |
460 1 << PG_reserved )))
461 bad_page(__FUNCTION__, page);
462
463 page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
464 1 << PG_referenced | 1 << PG_arch_1 |
465 1 << PG_checked | 1 << PG_mappedtodisk);
268 * So when we are allocating or freeing one, we can derive the state of the
269 * other. That is, if we allocate a small block, and both were
270 * free, the remainder of the region must be split into blocks.
271 * If a block is freed, and its buddy is also free, then this
272 * triggers coalescing into a block of larger size.
273 *
274 * -- wli
275 */

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458 1 << PG_swapcache |
459 1 << PG_writeback |
460 1 << PG_reserved )))
461 bad_page(__FUNCTION__, page);
462
463 page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
464 1 << PG_referenced | 1 << PG_arch_1 |
465 1 << PG_checked | 1 << PG_mappedtodisk);
466 page->private = 0;
466 set_page_private(page, 0);
467 set_page_refs(page, order);
468 kernel_map_pages(page, 1 << order, 1);
469}
470
471/*
472 * Do the hard work of removing an element from the buddy allocator.
473 * Call me with the zone->lock already held.
474 */

--- 2100 unchanged lines hidden --- 		467 set_page_refs(page, order);
468 kernel_map_pages(page, 1 << order, 1);
469}
470
471/*
472 * Do the hard work of removing an element from the buddy allocator.
473 * Call me with the zone->lock already held.
474 */

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