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Linux/mm/page_ext.c

  1 #include <linux/mm.h>
  2 #include <linux/mmzone.h>
  3 #include <linux/bootmem.h>
  4 #include <linux/page_ext.h>
  5 #include <linux/memory.h>
  6 #include <linux/vmalloc.h>
  7 #include <linux/kmemleak.h>
  8 #include <linux/page_owner.h>
  9 #include <linux/page_idle.h>
 10 
 11 /*
 12  * struct page extension
 13  *
 14  * This is the feature to manage memory for extended data per page.
 15  *
 16  * Until now, we must modify struct page itself to store extra data per page.
 17  * This requires rebuilding the kernel and it is really time consuming process.
 18  * And, sometimes, rebuild is impossible due to third party module dependency.
 19  * At last, enlarging struct page could cause un-wanted system behaviour change.
 20  *
 21  * This feature is intended to overcome above mentioned problems. This feature
 22  * allocates memory for extended data per page in certain place rather than
 23  * the struct page itself. This memory can be accessed by the accessor
 24  * functions provided by this code. During the boot process, it checks whether
 25  * allocation of huge chunk of memory is needed or not. If not, it avoids
 26  * allocating memory at all. With this advantage, we can include this feature
 27  * into the kernel in default and can avoid rebuild and solve related problems.
 28  *
 29  * To help these things to work well, there are two callbacks for clients. One
 30  * is the need callback which is mandatory if user wants to avoid useless
 31  * memory allocation at boot-time. The other is optional, init callback, which
 32  * is used to do proper initialization after memory is allocated.
 33  *
 34  * The need callback is used to decide whether extended memory allocation is
 35  * needed or not. Sometimes users want to deactivate some features in this
 36  * boot and extra memory would be unneccessary. In this case, to avoid
 37  * allocating huge chunk of memory, each clients represent their need of
 38  * extra memory through the need callback. If one of the need callbacks
 39  * returns true, it means that someone needs extra memory so that
 40  * page extension core should allocates memory for page extension. If
 41  * none of need callbacks return true, memory isn't needed at all in this boot
 42  * and page extension core can skip to allocate memory. As result,
 43  * none of memory is wasted.
 44  *
 45  * When need callback returns true, page_ext checks if there is a request for
 46  * extra memory through size in struct page_ext_operations. If it is non-zero,
 47  * extra space is allocated for each page_ext entry and offset is returned to
 48  * user through offset in struct page_ext_operations.
 49  *
 50  * The init callback is used to do proper initialization after page extension
 51  * is completely initialized. In sparse memory system, extra memory is
 52  * allocated some time later than memmap is allocated. In other words, lifetime
 53  * of memory for page extension isn't same with memmap for struct page.
 54  * Therefore, clients can't store extra data until page extension is
 55  * initialized, even if pages are allocated and used freely. This could
 56  * cause inadequate state of extra data per page, so, to prevent it, client
 57  * can utilize this callback to initialize the state of it correctly.
 58  */
 59 
 60 static struct page_ext_operations *page_ext_ops[] = {
 61         &debug_guardpage_ops,
 62 #ifdef CONFIG_PAGE_POISONING
 63         &page_poisoning_ops,
 64 #endif
 65 #ifdef CONFIG_PAGE_OWNER
 66         &page_owner_ops,
 67 #endif
 68 #if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
 69         &page_idle_ops,
 70 #endif
 71 };
 72 
 73 static unsigned long total_usage;
 74 static unsigned long extra_mem;
 75 
 76 static bool __init invoke_need_callbacks(void)
 77 {
 78         int i;
 79         int entries = ARRAY_SIZE(page_ext_ops);
 80         bool need = false;
 81 
 82         for (i = 0; i < entries; i++) {
 83                 if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
 84                         page_ext_ops[i]->offset = sizeof(struct page_ext) +
 85                                                 extra_mem;
 86                         extra_mem += page_ext_ops[i]->size;
 87                         need = true;
 88                 }
 89         }
 90 
 91         return need;
 92 }
 93 
 94 static void __init invoke_init_callbacks(void)
 95 {
 96         int i;
 97         int entries = ARRAY_SIZE(page_ext_ops);
 98 
 99         for (i = 0; i < entries; i++) {
100                 if (page_ext_ops[i]->init)
101                         page_ext_ops[i]->init();
102         }
103 }
104 
105 static unsigned long get_entry_size(void)
106 {
107         return sizeof(struct page_ext) + extra_mem;
108 }
109 
110 static inline struct page_ext *get_entry(void *base, unsigned long index)
111 {
112         return base + get_entry_size() * index;
113 }
114 
115 #if !defined(CONFIG_SPARSEMEM)
116 
117 
118 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
119 {
120         pgdat->node_page_ext = NULL;
121 }
122 
123 struct page_ext *lookup_page_ext(struct page *page)
124 {
125         unsigned long pfn = page_to_pfn(page);
126         unsigned long index;
127         struct page_ext *base;
128 
129         base = NODE_DATA(page_to_nid(page))->node_page_ext;
130 #if defined(CONFIG_DEBUG_VM) || defined(CONFIG_PAGE_POISONING)
131         /*
132          * The sanity checks the page allocator does upon freeing a
133          * page can reach here before the page_ext arrays are
134          * allocated when feeding a range of pages to the allocator
135          * for the first time during bootup or memory hotplug.
136          *
137          * This check is also necessary for ensuring page poisoning
138          * works as expected when enabled
139          */
140         if (unlikely(!base))
141                 return NULL;
142 #endif
143         index = pfn - round_down(node_start_pfn(page_to_nid(page)),
144                                         MAX_ORDER_NR_PAGES);
145         return get_entry(base, index);
146 }
147 
148 static int __init alloc_node_page_ext(int nid)
149 {
150         struct page_ext *base;
151         unsigned long table_size;
152         unsigned long nr_pages;
153 
154         nr_pages = NODE_DATA(nid)->node_spanned_pages;
155         if (!nr_pages)
156                 return 0;
157 
158         /*
159          * Need extra space if node range is not aligned with
160          * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
161          * checks buddy's status, range could be out of exact node range.
162          */
163         if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
164                 !IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
165                 nr_pages += MAX_ORDER_NR_PAGES;
166 
167         table_size = get_entry_size() * nr_pages;
168 
169         base = memblock_virt_alloc_try_nid_nopanic(
170                         table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
171                         BOOTMEM_ALLOC_ACCESSIBLE, nid);
172         if (!base)
173                 return -ENOMEM;
174         NODE_DATA(nid)->node_page_ext = base;
175         total_usage += table_size;
176         return 0;
177 }
178 
179 void __init page_ext_init_flatmem(void)
180 {
181 
182         int nid, fail;
183 
184         if (!invoke_need_callbacks())
185                 return;
186 
187         for_each_online_node(nid)  {
188                 fail = alloc_node_page_ext(nid);
189                 if (fail)
190                         goto fail;
191         }
192         pr_info("allocated %ld bytes of page_ext\n", total_usage);
193         invoke_init_callbacks();
194         return;
195 
196 fail:
197         pr_crit("allocation of page_ext failed.\n");
198         panic("Out of memory");
199 }
200 
201 #else /* CONFIG_FLAT_NODE_MEM_MAP */
202 
203 struct page_ext *lookup_page_ext(struct page *page)
204 {
205         unsigned long pfn = page_to_pfn(page);
206         struct mem_section *section = __pfn_to_section(pfn);
207 #if defined(CONFIG_DEBUG_VM) || defined(CONFIG_PAGE_POISONING)
208         /*
209          * The sanity checks the page allocator does upon freeing a
210          * page can reach here before the page_ext arrays are
211          * allocated when feeding a range of pages to the allocator
212          * for the first time during bootup or memory hotplug.
213          *
214          * This check is also necessary for ensuring page poisoning
215          * works as expected when enabled
216          */
217         if (!section->page_ext)
218                 return NULL;
219 #endif
220         return get_entry(section->page_ext, pfn);
221 }
222 
223 static void *__meminit alloc_page_ext(size_t size, int nid)
224 {
225         gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
226         void *addr = NULL;
227 
228         addr = alloc_pages_exact_nid(nid, size, flags);
229         if (addr) {
230                 kmemleak_alloc(addr, size, 1, flags);
231                 return addr;
232         }
233 
234         if (node_state(nid, N_HIGH_MEMORY))
235                 addr = vzalloc_node(size, nid);
236         else
237                 addr = vzalloc(size);
238 
239         return addr;
240 }
241 
242 static int __meminit init_section_page_ext(unsigned long pfn, int nid)
243 {
244         struct mem_section *section;
245         struct page_ext *base;
246         unsigned long table_size;
247 
248         section = __pfn_to_section(pfn);
249 
250         if (section->page_ext)
251                 return 0;
252 
253         table_size = get_entry_size() * PAGES_PER_SECTION;
254         base = alloc_page_ext(table_size, nid);
255 
256         /*
257          * The value stored in section->page_ext is (base - pfn)
258          * and it does not point to the memory block allocated above,
259          * causing kmemleak false positives.
260          */
261         kmemleak_not_leak(base);
262 
263         if (!base) {
264                 pr_err("page ext allocation failure\n");
265                 return -ENOMEM;
266         }
267 
268         /*
269          * The passed "pfn" may not be aligned to SECTION.  For the calculation
270          * we need to apply a mask.
271          */
272         pfn &= PAGE_SECTION_MASK;
273         section->page_ext = (void *)base - get_entry_size() * pfn;
274         total_usage += table_size;
275         return 0;
276 }
277 #ifdef CONFIG_MEMORY_HOTPLUG
278 static void free_page_ext(void *addr)
279 {
280         if (is_vmalloc_addr(addr)) {
281                 vfree(addr);
282         } else {
283                 struct page *page = virt_to_page(addr);
284                 size_t table_size;
285 
286                 table_size = get_entry_size() * PAGES_PER_SECTION;
287 
288                 BUG_ON(PageReserved(page));
289                 free_pages_exact(addr, table_size);
290         }
291 }
292 
293 static void __free_page_ext(unsigned long pfn)
294 {
295         struct mem_section *ms;
296         struct page_ext *base;
297 
298         ms = __pfn_to_section(pfn);
299         if (!ms || !ms->page_ext)
300                 return;
301         base = get_entry(ms->page_ext, pfn);
302         free_page_ext(base);
303         ms->page_ext = NULL;
304 }
305 
306 static int __meminit online_page_ext(unsigned long start_pfn,
307                                 unsigned long nr_pages,
308                                 int nid)
309 {
310         unsigned long start, end, pfn;
311         int fail = 0;
312 
313         start = SECTION_ALIGN_DOWN(start_pfn);
314         end = SECTION_ALIGN_UP(start_pfn + nr_pages);
315 
316         if (nid == -1) {
317                 /*
318                  * In this case, "nid" already exists and contains valid memory.
319                  * "start_pfn" passed to us is a pfn which is an arg for
320                  * online__pages(), and start_pfn should exist.
321                  */
322                 nid = pfn_to_nid(start_pfn);
323                 VM_BUG_ON(!node_state(nid, N_ONLINE));
324         }
325 
326         for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
327                 if (!pfn_present(pfn))
328                         continue;
329                 fail = init_section_page_ext(pfn, nid);
330         }
331         if (!fail)
332                 return 0;
333 
334         /* rollback */
335         for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
336                 __free_page_ext(pfn);
337 
338         return -ENOMEM;
339 }
340 
341 static int __meminit offline_page_ext(unsigned long start_pfn,
342                                 unsigned long nr_pages, int nid)
343 {
344         unsigned long start, end, pfn;
345 
346         start = SECTION_ALIGN_DOWN(start_pfn);
347         end = SECTION_ALIGN_UP(start_pfn + nr_pages);
348 
349         for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
350                 __free_page_ext(pfn);
351         return 0;
352 
353 }
354 
355 static int __meminit page_ext_callback(struct notifier_block *self,
356                                unsigned long action, void *arg)
357 {
358         struct memory_notify *mn = arg;
359         int ret = 0;
360 
361         switch (action) {
362         case MEM_GOING_ONLINE:
363                 ret = online_page_ext(mn->start_pfn,
364                                    mn->nr_pages, mn->status_change_nid);
365                 break;
366         case MEM_OFFLINE:
367                 offline_page_ext(mn->start_pfn,
368                                 mn->nr_pages, mn->status_change_nid);
369                 break;
370         case MEM_CANCEL_ONLINE:
371                 offline_page_ext(mn->start_pfn,
372                                 mn->nr_pages, mn->status_change_nid);
373                 break;
374         case MEM_GOING_OFFLINE:
375                 break;
376         case MEM_ONLINE:
377         case MEM_CANCEL_OFFLINE:
378                 break;
379         }
380 
381         return notifier_from_errno(ret);
382 }
383 
384 #endif
385 
386 void __init page_ext_init(void)
387 {
388         unsigned long pfn;
389         int nid;
390 
391         if (!invoke_need_callbacks())
392                 return;
393 
394         for_each_node_state(nid, N_MEMORY) {
395                 unsigned long start_pfn, end_pfn;
396 
397                 start_pfn = node_start_pfn(nid);
398                 end_pfn = node_end_pfn(nid);
399                 /*
400                  * start_pfn and end_pfn may not be aligned to SECTION and the
401                  * page->flags of out of node pages are not initialized.  So we
402                  * scan [start_pfn, the biggest section's pfn < end_pfn) here.
403                  */
404                 for (pfn = start_pfn; pfn < end_pfn;
405                         pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
406 
407                         if (!pfn_valid(pfn))
408                                 continue;
409                         /*
410                          * Nodes's pfns can be overlapping.
411                          * We know some arch can have a nodes layout such as
412                          * -------------pfn-------------->
413                          * N0 | N1 | N2 | N0 | N1 | N2|....
414                          *
415                          * Take into account DEFERRED_STRUCT_PAGE_INIT.
416                          */
417                         if (early_pfn_to_nid(pfn) != nid)
418                                 continue;
419                         if (init_section_page_ext(pfn, nid))
420                                 goto oom;
421                 }
422         }
423         hotplug_memory_notifier(page_ext_callback, 0);
424         pr_info("allocated %ld bytes of page_ext\n", total_usage);
425         invoke_init_callbacks();
426         return;
427 
428 oom:
429         panic("Out of memory");
430 }
431 
432 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
433 {
434 }
435 
436 #endif
437 

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