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