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