root/mm/page_ext.c

DEFINITIONS

1. invoke_need_callbacks
2. invoke_init_callbacks
3. get_entry
4. pgdat_page_ext_init
5. lookup_page_ext
6. alloc_node_page_ext
7. page_ext_init_flatmem
8. lookup_page_ext
9. alloc_page_ext
10. init_section_page_ext
11. free_page_ext
12. __free_page_ext
13. online_page_ext
14. offline_page_ext
15. page_ext_callback
16. page_ext_init
17. pgdat_page_ext_init

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/mm.h>
   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 
  12 /*
  13  * struct page extension
  14  *
  15  * This is the feature to manage memory for extended data per page.
  16  *
  17  * Until now, we must modify struct page itself to store extra data per page.
  18  * This requires rebuilding the kernel and it is really time consuming process.
  19  * And, sometimes, rebuild is impossible due to third party module dependency.
  20  * At last, enlarging struct page could cause un-wanted system behaviour change.
  21  *
  22  * This feature is intended to overcome above mentioned problems. This feature
  23  * allocates memory for extended data per page in certain place rather than
  24  * the struct page itself. This memory can be accessed by the accessor
  25  * functions provided by this code. During the boot process, it checks whether
  26  * allocation of huge chunk of memory is needed or not. If not, it avoids
  27  * allocating memory at all. With this advantage, we can include this feature
  28  * into the kernel in default and can avoid rebuild and solve related problems.
  29  *
  30  * To help these things to work well, there are two callbacks for clients. One
  31  * is the need callback which is mandatory if user wants to avoid useless
  32  * memory allocation at boot-time. The other is optional, init callback, which
  33  * is used to do proper initialization after memory is allocated.
  34  *
  35  * The need callback is used to decide whether extended memory allocation is
  36  * needed or not. Sometimes users want to deactivate some features in this
  37  * boot and extra memory would be unneccessary. In this case, to avoid
  38  * allocating huge chunk of memory, each clients represent their need of
  39  * extra memory through the need callback. If one of the need callbacks
  40  * returns true, it means that someone needs extra memory so that
  41  * page extension core should allocates memory for page extension. If
  42  * none of need callbacks return true, memory isn't needed at all in this boot
  43  * and page extension core can skip to allocate memory. As result,
  44  * none of memory is wasted.
  45  *
  46  * When need callback returns true, page_ext checks if there is a request for
  47  * extra memory through size in struct page_ext_operations. If it is non-zero,
  48  * extra space is allocated for each page_ext entry and offset is returned to
  49  * user through offset in struct page_ext_operations.
  50  *
  51  * The init callback is used to do proper initialization after page extension
  52  * is completely initialized. In sparse memory system, extra memory is
  53  * allocated some time later than memmap is allocated. In other words, lifetime
  54  * of memory for page extension isn't same with memmap for struct page.
  55  * Therefore, clients can't store extra data until page extension is
  56  * initialized, even if pages are allocated and used freely. This could
  57  * cause inadequate state of extra data per page, so, to prevent it, client
  58  * can utilize this callback to initialize the state of it correctly.
  59  */
  60 
  61 static struct page_ext_operations *page_ext_ops[] = {
  62 #ifdef CONFIG_PAGE_OWNER
  63         &page_owner_ops,
  64 #endif
  65 #if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
  66         &page_idle_ops,
  67 #endif
  68 };
  69 
  70 unsigned long page_ext_size = sizeof(struct page_ext);
  71 
  72 static unsigned long total_usage;
  73 
  74 static bool __init invoke_need_callbacks(void)
  75 {
  76         int i;
  77         int entries = ARRAY_SIZE(page_ext_ops);
  78         bool need = false;
  79 
  80         for (i = 0; i < entries; i++) {
  81                 if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
  82                         page_ext_ops[i]->offset = page_ext_size;
  83                         page_ext_size += page_ext_ops[i]->size;
  84                         need = true;
  85                 }
  86         }
  87 
  88         return need;
  89 }
  90 
  91 static void __init invoke_init_callbacks(void)
  92 {
  93         int i;
  94         int entries = ARRAY_SIZE(page_ext_ops);
  95 
  96         for (i = 0; i < entries; i++) {
  97                 if (page_ext_ops[i]->init)
  98                         page_ext_ops[i]->init();
  99         }
 100 }
 101 
 102 static inline struct page_ext *get_entry(void *base, unsigned long index)
 103 {
 104         return base + page_ext_size * index;
 105 }
 106 
 107 #if !defined(CONFIG_SPARSEMEM)
 108 
 109 
 110 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
 111 {
 112         pgdat->node_page_ext = NULL;
 113 }
 114 
 115 struct page_ext *lookup_page_ext(const struct page *page)
 116 {
 117         unsigned long pfn = page_to_pfn(page);
 118         unsigned long index;
 119         struct page_ext *base;
 120 
 121         base = NODE_DATA(page_to_nid(page))->node_page_ext;
 122         /*
 123          * The sanity checks the page allocator does upon freeing a
 124          * page can reach here before the page_ext arrays are
 125          * allocated when feeding a range of pages to the allocator
 126          * for the first time during bootup or memory hotplug.
 127          */
 128         if (unlikely(!base))
 129                 return NULL;
 130         index = pfn - round_down(node_start_pfn(page_to_nid(page)),
 131                                         MAX_ORDER_NR_PAGES);
 132         return get_entry(base, index);
 133 }
 134 
 135 static int __init alloc_node_page_ext(int nid)
 136 {
 137         struct page_ext *base;
 138         unsigned long table_size;
 139         unsigned long nr_pages;
 140 
 141         nr_pages = NODE_DATA(nid)->node_spanned_pages;
 142         if (!nr_pages)
 143                 return 0;
 144 
 145         /*
 146          * Need extra space if node range is not aligned with
 147          * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
 148          * checks buddy's status, range could be out of exact node range.
 149          */
 150         if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
 151                 !IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
 152                 nr_pages += MAX_ORDER_NR_PAGES;
 153 
 154         table_size = page_ext_size * nr_pages;
 155 
 156         base = memblock_alloc_try_nid(
 157                         table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
 158                         MEMBLOCK_ALLOC_ACCESSIBLE, nid);
 159         if (!base)
 160                 return -ENOMEM;
 161         NODE_DATA(nid)->node_page_ext = base;
 162         total_usage += table_size;
 163         return 0;
 164 }
 165 
 166 void __init page_ext_init_flatmem(void)
 167 {
 168 
 169         int nid, fail;
 170 
 171         if (!invoke_need_callbacks())
 172                 return;
 173 
 174         for_each_online_node(nid)  {
 175                 fail = alloc_node_page_ext(nid);
 176                 if (fail)
 177                         goto fail;
 178         }
 179         pr_info("allocated %ld bytes of page_ext\n", total_usage);
 180         invoke_init_callbacks();
 181         return;
 182 
 183 fail:
 184         pr_crit("allocation of page_ext failed.\n");
 185         panic("Out of memory");
 186 }
 187 
 188 #else /* CONFIG_FLAT_NODE_MEM_MAP */
 189 
 190 struct page_ext *lookup_page_ext(const struct page *page)
 191 {
 192         unsigned long pfn = page_to_pfn(page);
 193         struct mem_section *section = __pfn_to_section(pfn);
 194         /*
 195          * The sanity checks the page allocator does upon freeing a
 196          * page can reach here before the page_ext arrays are
 197          * allocated when feeding a range of pages to the allocator
 198          * for the first time during bootup or memory hotplug.
 199          */
 200         if (!section->page_ext)
 201                 return NULL;
 202         return get_entry(section->page_ext, pfn);
 203 }
 204 
 205 static void *__meminit alloc_page_ext(size_t size, int nid)
 206 {
 207         gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
 208         void *addr = NULL;
 209 
 210         addr = alloc_pages_exact_nid(nid, size, flags);
 211         if (addr) {
 212                 kmemleak_alloc(addr, size, 1, flags);
 213                 return addr;
 214         }
 215 
 216         addr = vzalloc_node(size, nid);
 217 
 218         return addr;
 219 }
 220 
 221 static int __meminit init_section_page_ext(unsigned long pfn, int nid)
 222 {
 223         struct mem_section *section;
 224         struct page_ext *base;
 225         unsigned long table_size;
 226 
 227         section = __pfn_to_section(pfn);
 228 
 229         if (section->page_ext)
 230                 return 0;
 231 
 232         table_size = page_ext_size * PAGES_PER_SECTION;
 233         base = alloc_page_ext(table_size, nid);
 234 
 235         /*
 236          * The value stored in section->page_ext is (base - pfn)
 237          * and it does not point to the memory block allocated above,
 238          * causing kmemleak false positives.
 239          */
 240         kmemleak_not_leak(base);
 241 
 242         if (!base) {
 243                 pr_err("page ext allocation failure\n");
 244                 return -ENOMEM;
 245         }
 246 
 247         /*
 248          * The passed "pfn" may not be aligned to SECTION.  For the calculation
 249          * we need to apply a mask.
 250          */
 251         pfn &= PAGE_SECTION_MASK;
 252         section->page_ext = (void *)base - page_ext_size * pfn;
 253         total_usage += table_size;
 254         return 0;
 255 }
 256 #ifdef CONFIG_MEMORY_HOTPLUG
 257 static void free_page_ext(void *addr)
 258 {
 259         if (is_vmalloc_addr(addr)) {
 260                 vfree(addr);
 261         } else {
 262                 struct page *page = virt_to_page(addr);
 263                 size_t table_size;
 264 
 265                 table_size = page_ext_size * PAGES_PER_SECTION;
 266 
 267                 BUG_ON(PageReserved(page));
 268                 kmemleak_free(addr);
 269                 free_pages_exact(addr, table_size);
 270         }
 271 }
 272 
 273 static void __free_page_ext(unsigned long pfn)
 274 {
 275         struct mem_section *ms;
 276         struct page_ext *base;
 277 
 278         ms = __pfn_to_section(pfn);
 279         if (!ms || !ms->page_ext)
 280                 return;
 281         base = get_entry(ms->page_ext, pfn);
 282         free_page_ext(base);
 283         ms->page_ext = NULL;
 284 }
 285 
 286 static int __meminit online_page_ext(unsigned long start_pfn,
 287                                 unsigned long nr_pages,
 288                                 int nid)
 289 {
 290         unsigned long start, end, pfn;
 291         int fail = 0;
 292 
 293         start = SECTION_ALIGN_DOWN(start_pfn);
 294         end = SECTION_ALIGN_UP(start_pfn + nr_pages);
 295 
 296         if (nid == NUMA_NO_NODE) {
 297                 /*
 298                  * In this case, "nid" already exists and contains valid memory.
 299                  * "start_pfn" passed to us is a pfn which is an arg for
 300                  * online__pages(), and start_pfn should exist.
 301                  */
 302                 nid = pfn_to_nid(start_pfn);
 303                 VM_BUG_ON(!node_state(nid, N_ONLINE));
 304         }
 305 
 306         for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
 307                 if (!pfn_present(pfn))
 308                         continue;
 309                 fail = init_section_page_ext(pfn, nid);
 310         }
 311         if (!fail)
 312                 return 0;
 313 
 314         /* rollback */
 315         for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
 316                 __free_page_ext(pfn);
 317 
 318         return -ENOMEM;
 319 }
 320 
 321 static int __meminit offline_page_ext(unsigned long start_pfn,
 322                                 unsigned long nr_pages, int nid)
 323 {
 324         unsigned long start, end, pfn;
 325 
 326         start = SECTION_ALIGN_DOWN(start_pfn);
 327         end = SECTION_ALIGN_UP(start_pfn + nr_pages);
 328 
 329         for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
 330                 __free_page_ext(pfn);
 331         return 0;
 332 
 333 }
 334 
 335 static int __meminit page_ext_callback(struct notifier_block *self,
 336                                unsigned long action, void *arg)
 337 {
 338         struct memory_notify *mn = arg;
 339         int ret = 0;
 340 
 341         switch (action) {
 342         case MEM_GOING_ONLINE:
 343                 ret = online_page_ext(mn->start_pfn,
 344                                    mn->nr_pages, mn->status_change_nid);
 345                 break;
 346         case MEM_OFFLINE:
 347                 offline_page_ext(mn->start_pfn,
 348                                 mn->nr_pages, mn->status_change_nid);
 349                 break;
 350         case MEM_CANCEL_ONLINE:
 351                 offline_page_ext(mn->start_pfn,
 352                                 mn->nr_pages, mn->status_change_nid);
 353                 break;
 354         case MEM_GOING_OFFLINE:
 355                 break;
 356         case MEM_ONLINE:
 357         case MEM_CANCEL_OFFLINE:
 358                 break;
 359         }
 360 
 361         return notifier_from_errno(ret);
 362 }
 363 
 364 #endif
 365 
 366 void __init page_ext_init(void)
 367 {
 368         unsigned long pfn;
 369         int nid;
 370 
 371         if (!invoke_need_callbacks())
 372                 return;
 373 
 374         for_each_node_state(nid, N_MEMORY) {
 375                 unsigned long start_pfn, end_pfn;
 376 
 377                 start_pfn = node_start_pfn(nid);
 378                 end_pfn = node_end_pfn(nid);
 379                 /*
 380                  * start_pfn and end_pfn may not be aligned to SECTION and the
 381                  * page->flags of out of node pages are not initialized.  So we
 382                  * scan [start_pfn, the biggest section's pfn < end_pfn) here.
 383                  */
 384                 for (pfn = start_pfn; pfn < end_pfn;
 385                         pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
 386 
 387                         if (!pfn_valid(pfn))
 388                                 continue;
 389                         /*
 390                          * Nodes's pfns can be overlapping.
 391                          * We know some arch can have a nodes layout such as
 392                          * -------------pfn-------------->
 393                          * N0 | N1 | N2 | N0 | N1 | N2|....
 394                          */
 395                         if (pfn_to_nid(pfn) != nid)
 396                                 continue;
 397                         if (init_section_page_ext(pfn, nid))
 398                                 goto oom;
 399                         cond_resched();
 400                 }
 401         }
 402         hotplug_memory_notifier(page_ext_callback, 0);
 403         pr_info("allocated %ld bytes of page_ext\n", total_usage);
 404         invoke_init_callbacks();
 405         return;
 406 
 407 oom:
 408         panic("Out of memory");
 409 }
 410 
 411 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
 412 {
 413 }
 414 
 415 #endif