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