1 // SPDX-License-Identifier: GPL-2.0
3 #include <linux/mmzone.h>
4 #include <linux/memblock.h>
5 #include <linux/page_ext.h>
6 #include <linux/memory.h>
7 #include <linux/vmalloc.h>
8 #include <linux/kmemleak.h>
9 #include <linux/page_owner.h>
10 #include <linux/page_idle.h>
11 #include <linux/page_table_check.h>
12 #include <linux/rcupdate.h>
15 * struct page extension
17 * This is the feature to manage memory for extended data per page.
19 * Until now, we must modify struct page itself to store extra data per page.
20 * This requires rebuilding the kernel and it is really time consuming process.
21 * And, sometimes, rebuild is impossible due to third party module dependency.
22 * At last, enlarging struct page could cause un-wanted system behaviour change.
24 * This feature is intended to overcome above mentioned problems. This feature
25 * allocates memory for extended data per page in certain place rather than
26 * the struct page itself. This memory can be accessed by the accessor
27 * functions provided by this code. During the boot process, it checks whether
28 * allocation of huge chunk of memory is needed or not. If not, it avoids
29 * allocating memory at all. With this advantage, we can include this feature
30 * into the kernel in default and can avoid rebuild and solve related problems.
32 * To help these things to work well, there are two callbacks for clients. One
33 * is the need callback which is mandatory if user wants to avoid useless
34 * memory allocation at boot-time. The other is optional, init callback, which
35 * is used to do proper initialization after memory is allocated.
37 * The need callback is used to decide whether extended memory allocation is
38 * needed or not. Sometimes users want to deactivate some features in this
39 * boot and extra memory would be unnecessary. In this case, to avoid
40 * allocating huge chunk of memory, each clients represent their need of
41 * extra memory through the need callback. If one of the need callbacks
42 * returns true, it means that someone needs extra memory so that
43 * page extension core should allocates memory for page extension. If
44 * none of need callbacks return true, memory isn't needed at all in this boot
45 * and page extension core can skip to allocate memory. As result,
46 * none of memory is wasted.
48 * When need callback returns true, page_ext checks if there is a request for
49 * extra memory through size in struct page_ext_operations. If it is non-zero,
50 * extra space is allocated for each page_ext entry and offset is returned to
51 * user through offset in struct page_ext_operations.
53 * The init callback is used to do proper initialization after page extension
54 * is completely initialized. In sparse memory system, extra memory is
55 * allocated some time later than memmap is allocated. In other words, lifetime
56 * of memory for page extension isn't same with memmap for struct page.
57 * Therefore, clients can't store extra data until page extension is
58 * initialized, even if pages are allocated and used freely. This could
59 * cause inadequate state of extra data per page, so, to prevent it, client
60 * can utilize this callback to initialize the state of it correctly.
63 #ifdef CONFIG_SPARSEMEM
64 #define PAGE_EXT_INVALID (0x1)
67 #if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
68 static bool need_page_idle(void)
72 static struct page_ext_operations page_idle_ops __initdata
= {
73 .need
= need_page_idle
,
74 .need_shared_flags
= true,
78 static struct page_ext_operations
*page_ext_ops
[] __initdata
= {
79 #ifdef CONFIG_PAGE_OWNER
82 #if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
85 #ifdef CONFIG_PAGE_TABLE_CHECK
86 &page_table_check_ops
,
90 unsigned long page_ext_size
;
92 static unsigned long total_usage
;
94 bool early_page_ext __meminitdata
;
95 static int __init
setup_early_page_ext(char *str
)
97 early_page_ext
= true;
100 early_param("early_page_ext", setup_early_page_ext
);
102 static bool __init
invoke_need_callbacks(void)
105 int entries
= ARRAY_SIZE(page_ext_ops
);
108 for (i
= 0; i
< entries
; i
++) {
109 if (page_ext_ops
[i
]->need()) {
110 if (page_ext_ops
[i
]->need_shared_flags
) {
111 page_ext_size
= sizeof(struct page_ext
);
117 for (i
= 0; i
< entries
; i
++) {
118 if (page_ext_ops
[i
]->need()) {
119 page_ext_ops
[i
]->offset
= page_ext_size
;
120 page_ext_size
+= page_ext_ops
[i
]->size
;
128 static void __init
invoke_init_callbacks(void)
131 int entries
= ARRAY_SIZE(page_ext_ops
);
133 for (i
= 0; i
< entries
; i
++) {
134 if (page_ext_ops
[i
]->init
)
135 page_ext_ops
[i
]->init();
139 static inline struct page_ext
*get_entry(void *base
, unsigned long index
)
141 return base
+ page_ext_size
* index
;
144 #ifndef CONFIG_SPARSEMEM
145 void __init
page_ext_init_flatmem_late(void)
147 invoke_init_callbacks();
150 void __meminit
pgdat_page_ext_init(struct pglist_data
*pgdat
)
152 pgdat
->node_page_ext
= NULL
;
155 static struct page_ext
*lookup_page_ext(const struct page
*page
)
157 unsigned long pfn
= page_to_pfn(page
);
159 struct page_ext
*base
;
161 WARN_ON_ONCE(!rcu_read_lock_held());
162 base
= NODE_DATA(page_to_nid(page
))->node_page_ext
;
164 * The sanity checks the page allocator does upon freeing a
165 * page can reach here before the page_ext arrays are
166 * allocated when feeding a range of pages to the allocator
167 * for the first time during bootup or memory hotplug.
171 index
= pfn
- round_down(node_start_pfn(page_to_nid(page
)),
173 return get_entry(base
, index
);
176 static int __init
alloc_node_page_ext(int nid
)
178 struct page_ext
*base
;
179 unsigned long table_size
;
180 unsigned long nr_pages
;
182 nr_pages
= NODE_DATA(nid
)->node_spanned_pages
;
187 * Need extra space if node range is not aligned with
188 * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
189 * checks buddy's status, range could be out of exact node range.
191 if (!IS_ALIGNED(node_start_pfn(nid
), MAX_ORDER_NR_PAGES
) ||
192 !IS_ALIGNED(node_end_pfn(nid
), MAX_ORDER_NR_PAGES
))
193 nr_pages
+= MAX_ORDER_NR_PAGES
;
195 table_size
= page_ext_size
* nr_pages
;
197 base
= memblock_alloc_try_nid(
198 table_size
, PAGE_SIZE
, __pa(MAX_DMA_ADDRESS
),
199 MEMBLOCK_ALLOC_ACCESSIBLE
, nid
);
202 NODE_DATA(nid
)->node_page_ext
= base
;
203 total_usage
+= table_size
;
207 void __init
page_ext_init_flatmem(void)
212 if (!invoke_need_callbacks())
215 for_each_online_node(nid
) {
216 fail
= alloc_node_page_ext(nid
);
220 pr_info("allocated %ld bytes of page_ext\n", total_usage
);
224 pr_crit("allocation of page_ext failed.\n");
225 panic("Out of memory");
228 #else /* CONFIG_SPARSEMEM */
229 static bool page_ext_invalid(struct page_ext
*page_ext
)
231 return !page_ext
|| (((unsigned long)page_ext
& PAGE_EXT_INVALID
) == PAGE_EXT_INVALID
);
234 static struct page_ext
*lookup_page_ext(const struct page
*page
)
236 unsigned long pfn
= page_to_pfn(page
);
237 struct mem_section
*section
= __pfn_to_section(pfn
);
238 struct page_ext
*page_ext
= READ_ONCE(section
->page_ext
);
240 WARN_ON_ONCE(!rcu_read_lock_held());
242 * The sanity checks the page allocator does upon freeing a
243 * page can reach here before the page_ext arrays are
244 * allocated when feeding a range of pages to the allocator
245 * for the first time during bootup or memory hotplug.
247 if (page_ext_invalid(page_ext
))
249 return get_entry(page_ext
, pfn
);
252 static void *__meminit
alloc_page_ext(size_t size
, int nid
)
254 gfp_t flags
= GFP_KERNEL
| __GFP_ZERO
| __GFP_NOWARN
;
257 addr
= alloc_pages_exact_nid(nid
, size
, flags
);
259 kmemleak_alloc(addr
, size
, 1, flags
);
263 addr
= vzalloc_node(size
, nid
);
268 static int __meminit
init_section_page_ext(unsigned long pfn
, int nid
)
270 struct mem_section
*section
;
271 struct page_ext
*base
;
272 unsigned long table_size
;
274 section
= __pfn_to_section(pfn
);
276 if (section
->page_ext
)
279 table_size
= page_ext_size
* PAGES_PER_SECTION
;
280 base
= alloc_page_ext(table_size
, nid
);
283 * The value stored in section->page_ext is (base - pfn)
284 * and it does not point to the memory block allocated above,
285 * causing kmemleak false positives.
287 kmemleak_not_leak(base
);
290 pr_err("page ext allocation failure\n");
295 * The passed "pfn" may not be aligned to SECTION. For the calculation
296 * we need to apply a mask.
298 pfn
&= PAGE_SECTION_MASK
;
299 section
->page_ext
= (void *)base
- page_ext_size
* pfn
;
300 total_usage
+= table_size
;
304 static void free_page_ext(void *addr
)
306 if (is_vmalloc_addr(addr
)) {
309 struct page
*page
= virt_to_page(addr
);
312 table_size
= page_ext_size
* PAGES_PER_SECTION
;
314 BUG_ON(PageReserved(page
));
316 free_pages_exact(addr
, table_size
);
320 static void __free_page_ext(unsigned long pfn
)
322 struct mem_section
*ms
;
323 struct page_ext
*base
;
325 ms
= __pfn_to_section(pfn
);
326 if (!ms
|| !ms
->page_ext
)
329 base
= READ_ONCE(ms
->page_ext
);
331 * page_ext here can be valid while doing the roll back
332 * operation in online_page_ext().
334 if (page_ext_invalid(base
))
335 base
= (void *)base
- PAGE_EXT_INVALID
;
336 WRITE_ONCE(ms
->page_ext
, NULL
);
338 base
= get_entry(base
, pfn
);
342 static void __invalidate_page_ext(unsigned long pfn
)
344 struct mem_section
*ms
;
347 ms
= __pfn_to_section(pfn
);
348 if (!ms
|| !ms
->page_ext
)
350 val
= (void *)ms
->page_ext
+ PAGE_EXT_INVALID
;
351 WRITE_ONCE(ms
->page_ext
, val
);
354 static int __meminit
online_page_ext(unsigned long start_pfn
,
355 unsigned long nr_pages
,
358 unsigned long start
, end
, pfn
;
361 start
= SECTION_ALIGN_DOWN(start_pfn
);
362 end
= SECTION_ALIGN_UP(start_pfn
+ nr_pages
);
364 if (nid
== NUMA_NO_NODE
) {
366 * In this case, "nid" already exists and contains valid memory.
367 * "start_pfn" passed to us is a pfn which is an arg for
368 * online__pages(), and start_pfn should exist.
370 nid
= pfn_to_nid(start_pfn
);
371 VM_BUG_ON(!node_online(nid
));
374 for (pfn
= start
; !fail
&& pfn
< end
; pfn
+= PAGES_PER_SECTION
)
375 fail
= init_section_page_ext(pfn
, nid
);
380 end
= pfn
- PAGES_PER_SECTION
;
381 for (pfn
= start
; pfn
< end
; pfn
+= PAGES_PER_SECTION
)
382 __free_page_ext(pfn
);
387 static void __meminit
offline_page_ext(unsigned long start_pfn
,
388 unsigned long nr_pages
)
390 unsigned long start
, end
, pfn
;
392 start
= SECTION_ALIGN_DOWN(start_pfn
);
393 end
= SECTION_ALIGN_UP(start_pfn
+ nr_pages
);
396 * Freeing of page_ext is done in 3 steps to avoid
397 * use-after-free of it:
398 * 1) Traverse all the sections and mark their page_ext
400 * 2) Wait for all the existing users of page_ext who
401 * started before invalidation to finish.
402 * 3) Free the page_ext.
404 for (pfn
= start
; pfn
< end
; pfn
+= PAGES_PER_SECTION
)
405 __invalidate_page_ext(pfn
);
409 for (pfn
= start
; pfn
< end
; pfn
+= PAGES_PER_SECTION
)
410 __free_page_ext(pfn
);
413 static int __meminit
page_ext_callback(struct notifier_block
*self
,
414 unsigned long action
, void *arg
)
416 struct memory_notify
*mn
= arg
;
420 case MEM_GOING_ONLINE
:
421 ret
= online_page_ext(mn
->start_pfn
,
422 mn
->nr_pages
, mn
->status_change_nid
);
425 offline_page_ext(mn
->start_pfn
,
428 case MEM_CANCEL_ONLINE
:
429 offline_page_ext(mn
->start_pfn
,
432 case MEM_GOING_OFFLINE
:
435 case MEM_CANCEL_OFFLINE
:
439 return notifier_from_errno(ret
);
442 void __init
page_ext_init(void)
447 if (!invoke_need_callbacks())
450 for_each_node_state(nid
, N_MEMORY
) {
451 unsigned long start_pfn
, end_pfn
;
453 start_pfn
= node_start_pfn(nid
);
454 end_pfn
= node_end_pfn(nid
);
456 * start_pfn and end_pfn may not be aligned to SECTION and the
457 * page->flags of out of node pages are not initialized. So we
458 * scan [start_pfn, the biggest section's pfn < end_pfn) here.
460 for (pfn
= start_pfn
; pfn
< end_pfn
;
461 pfn
= ALIGN(pfn
+ 1, PAGES_PER_SECTION
)) {
466 * Nodes's pfns can be overlapping.
467 * We know some arch can have a nodes layout such as
468 * -------------pfn-------------->
469 * N0 | N1 | N2 | N0 | N1 | N2|....
471 if (pfn_to_nid(pfn
) != nid
)
473 if (init_section_page_ext(pfn
, nid
))
478 hotplug_memory_notifier(page_ext_callback
, DEFAULT_CALLBACK_PRI
);
479 pr_info("allocated %ld bytes of page_ext\n", total_usage
);
480 invoke_init_callbacks();
484 panic("Out of memory");
487 void __meminit
pgdat_page_ext_init(struct pglist_data
*pgdat
)
494 * page_ext_get() - Get the extended information for a page.
495 * @page: The page we're interested in.
497 * Ensures that the page_ext will remain valid until page_ext_put()
500 * Return: NULL if no page_ext exists for this page.
501 * Context: Any context. Caller may not sleep until they have called
504 struct page_ext
*page_ext_get(struct page
*page
)
506 struct page_ext
*page_ext
;
509 page_ext
= lookup_page_ext(page
);
519 * page_ext_put() - Working with page extended information is done.
520 * @page_ext: Page extended information received from page_ext_get().
522 * The page extended information of the page may not be valid after this
523 * function is called.
526 * Context: Any context with corresponding page_ext_get() is called.
528 void page_ext_put(struct page_ext
*page_ext
)
530 if (unlikely(!page_ext
))