Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2009 Red Hat, Inc. |
| 3 | * |
| 4 | * This work is licensed under the terms of the GNU GPL, version 2. See |
| 5 | * the COPYING file in the top-level directory. |
| 6 | */ |
| 7 | |
| 8 | #include <linux/mm.h> |
| 9 | #include <linux/sched.h> |
| 10 | #include <linux/highmem.h> |
| 11 | #include <linux/hugetlb.h> |
| 12 | #include <linux/mmu_notifier.h> |
| 13 | #include <linux/rmap.h> |
| 14 | #include <linux/swap.h> |
| 15 | #include <asm/tlb.h> |
| 16 | #include <asm/pgalloc.h> |
| 17 | #include "internal.h" |
| 18 | |
| 19 | unsigned long transparent_hugepage_flags __read_mostly = |
| 20 | (1<<TRANSPARENT_HUGEPAGE_FLAG); |
| 21 | |
| 22 | #ifdef CONFIG_SYSFS |
| 23 | static ssize_t double_flag_show(struct kobject *kobj, |
| 24 | struct kobj_attribute *attr, char *buf, |
| 25 | enum transparent_hugepage_flag enabled, |
| 26 | enum transparent_hugepage_flag req_madv) |
| 27 | { |
| 28 | if (test_bit(enabled, &transparent_hugepage_flags)) { |
| 29 | VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); |
| 30 | return sprintf(buf, "[always] madvise never\n"); |
| 31 | } else if (test_bit(req_madv, &transparent_hugepage_flags)) |
| 32 | return sprintf(buf, "always [madvise] never\n"); |
| 33 | else |
| 34 | return sprintf(buf, "always madvise [never]\n"); |
| 35 | } |
| 36 | static ssize_t double_flag_store(struct kobject *kobj, |
| 37 | struct kobj_attribute *attr, |
| 38 | const char *buf, size_t count, |
| 39 | enum transparent_hugepage_flag enabled, |
| 40 | enum transparent_hugepage_flag req_madv) |
| 41 | { |
| 42 | if (!memcmp("always", buf, |
| 43 | min(sizeof("always")-1, count))) { |
| 44 | set_bit(enabled, &transparent_hugepage_flags); |
| 45 | clear_bit(req_madv, &transparent_hugepage_flags); |
| 46 | } else if (!memcmp("madvise", buf, |
| 47 | min(sizeof("madvise")-1, count))) { |
| 48 | clear_bit(enabled, &transparent_hugepage_flags); |
| 49 | set_bit(req_madv, &transparent_hugepage_flags); |
| 50 | } else if (!memcmp("never", buf, |
| 51 | min(sizeof("never")-1, count))) { |
| 52 | clear_bit(enabled, &transparent_hugepage_flags); |
| 53 | clear_bit(req_madv, &transparent_hugepage_flags); |
| 54 | } else |
| 55 | return -EINVAL; |
| 56 | |
| 57 | return count; |
| 58 | } |
| 59 | |
| 60 | static ssize_t enabled_show(struct kobject *kobj, |
| 61 | struct kobj_attribute *attr, char *buf) |
| 62 | { |
| 63 | return double_flag_show(kobj, attr, buf, |
| 64 | TRANSPARENT_HUGEPAGE_FLAG, |
| 65 | TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); |
| 66 | } |
| 67 | static ssize_t enabled_store(struct kobject *kobj, |
| 68 | struct kobj_attribute *attr, |
| 69 | const char *buf, size_t count) |
| 70 | { |
| 71 | return double_flag_store(kobj, attr, buf, count, |
| 72 | TRANSPARENT_HUGEPAGE_FLAG, |
| 73 | TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); |
| 74 | } |
| 75 | static struct kobj_attribute enabled_attr = |
| 76 | __ATTR(enabled, 0644, enabled_show, enabled_store); |
| 77 | |
| 78 | static ssize_t single_flag_show(struct kobject *kobj, |
| 79 | struct kobj_attribute *attr, char *buf, |
| 80 | enum transparent_hugepage_flag flag) |
| 81 | { |
| 82 | if (test_bit(flag, &transparent_hugepage_flags)) |
| 83 | return sprintf(buf, "[yes] no\n"); |
| 84 | else |
| 85 | return sprintf(buf, "yes [no]\n"); |
| 86 | } |
| 87 | static ssize_t single_flag_store(struct kobject *kobj, |
| 88 | struct kobj_attribute *attr, |
| 89 | const char *buf, size_t count, |
| 90 | enum transparent_hugepage_flag flag) |
| 91 | { |
| 92 | if (!memcmp("yes", buf, |
| 93 | min(sizeof("yes")-1, count))) { |
| 94 | set_bit(flag, &transparent_hugepage_flags); |
| 95 | } else if (!memcmp("no", buf, |
| 96 | min(sizeof("no")-1, count))) { |
| 97 | clear_bit(flag, &transparent_hugepage_flags); |
| 98 | } else |
| 99 | return -EINVAL; |
| 100 | |
| 101 | return count; |
| 102 | } |
| 103 | |
| 104 | /* |
| 105 | * Currently defrag only disables __GFP_NOWAIT for allocation. A blind |
| 106 | * __GFP_REPEAT is too aggressive, it's never worth swapping tons of |
| 107 | * memory just to allocate one more hugepage. |
| 108 | */ |
| 109 | static ssize_t defrag_show(struct kobject *kobj, |
| 110 | struct kobj_attribute *attr, char *buf) |
| 111 | { |
| 112 | return double_flag_show(kobj, attr, buf, |
| 113 | TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, |
| 114 | TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); |
| 115 | } |
| 116 | static ssize_t defrag_store(struct kobject *kobj, |
| 117 | struct kobj_attribute *attr, |
| 118 | const char *buf, size_t count) |
| 119 | { |
| 120 | return double_flag_store(kobj, attr, buf, count, |
| 121 | TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, |
| 122 | TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); |
| 123 | } |
| 124 | static struct kobj_attribute defrag_attr = |
| 125 | __ATTR(defrag, 0644, defrag_show, defrag_store); |
| 126 | |
| 127 | #ifdef CONFIG_DEBUG_VM |
| 128 | static ssize_t debug_cow_show(struct kobject *kobj, |
| 129 | struct kobj_attribute *attr, char *buf) |
| 130 | { |
| 131 | return single_flag_show(kobj, attr, buf, |
| 132 | TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); |
| 133 | } |
| 134 | static ssize_t debug_cow_store(struct kobject *kobj, |
| 135 | struct kobj_attribute *attr, |
| 136 | const char *buf, size_t count) |
| 137 | { |
| 138 | return single_flag_store(kobj, attr, buf, count, |
| 139 | TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); |
| 140 | } |
| 141 | static struct kobj_attribute debug_cow_attr = |
| 142 | __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); |
| 143 | #endif /* CONFIG_DEBUG_VM */ |
| 144 | |
| 145 | static struct attribute *hugepage_attr[] = { |
| 146 | &enabled_attr.attr, |
| 147 | &defrag_attr.attr, |
| 148 | #ifdef CONFIG_DEBUG_VM |
| 149 | &debug_cow_attr.attr, |
| 150 | #endif |
| 151 | NULL, |
| 152 | }; |
| 153 | |
| 154 | static struct attribute_group hugepage_attr_group = { |
| 155 | .attrs = hugepage_attr, |
| 156 | .name = "transparent_hugepage", |
| 157 | }; |
| 158 | #endif /* CONFIG_SYSFS */ |
| 159 | |
| 160 | static int __init hugepage_init(void) |
| 161 | { |
| 162 | #ifdef CONFIG_SYSFS |
| 163 | int err; |
| 164 | |
| 165 | err = sysfs_create_group(mm_kobj, &hugepage_attr_group); |
| 166 | if (err) |
| 167 | printk(KERN_ERR "hugepage: register sysfs failed\n"); |
| 168 | #endif |
| 169 | return 0; |
| 170 | } |
| 171 | module_init(hugepage_init) |
| 172 | |
| 173 | static int __init setup_transparent_hugepage(char *str) |
| 174 | { |
| 175 | int ret = 0; |
| 176 | if (!str) |
| 177 | goto out; |
| 178 | if (!strcmp(str, "always")) { |
| 179 | set_bit(TRANSPARENT_HUGEPAGE_FLAG, |
| 180 | &transparent_hugepage_flags); |
| 181 | clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, |
| 182 | &transparent_hugepage_flags); |
| 183 | ret = 1; |
| 184 | } else if (!strcmp(str, "madvise")) { |
| 185 | clear_bit(TRANSPARENT_HUGEPAGE_FLAG, |
| 186 | &transparent_hugepage_flags); |
| 187 | set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, |
| 188 | &transparent_hugepage_flags); |
| 189 | ret = 1; |
| 190 | } else if (!strcmp(str, "never")) { |
| 191 | clear_bit(TRANSPARENT_HUGEPAGE_FLAG, |
| 192 | &transparent_hugepage_flags); |
| 193 | clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, |
| 194 | &transparent_hugepage_flags); |
| 195 | ret = 1; |
| 196 | } |
| 197 | out: |
| 198 | if (!ret) |
| 199 | printk(KERN_WARNING |
| 200 | "transparent_hugepage= cannot parse, ignored\n"); |
| 201 | return ret; |
| 202 | } |
| 203 | __setup("transparent_hugepage=", setup_transparent_hugepage); |
| 204 | |
| 205 | static void prepare_pmd_huge_pte(pgtable_t pgtable, |
| 206 | struct mm_struct *mm) |
| 207 | { |
| 208 | assert_spin_locked(&mm->page_table_lock); |
| 209 | |
| 210 | /* FIFO */ |
| 211 | if (!mm->pmd_huge_pte) |
| 212 | INIT_LIST_HEAD(&pgtable->lru); |
| 213 | else |
| 214 | list_add(&pgtable->lru, &mm->pmd_huge_pte->lru); |
| 215 | mm->pmd_huge_pte = pgtable; |
| 216 | } |
| 217 | |
| 218 | static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) |
| 219 | { |
| 220 | if (likely(vma->vm_flags & VM_WRITE)) |
| 221 | pmd = pmd_mkwrite(pmd); |
| 222 | return pmd; |
| 223 | } |
| 224 | |
| 225 | static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, |
| 226 | struct vm_area_struct *vma, |
| 227 | unsigned long haddr, pmd_t *pmd, |
| 228 | struct page *page) |
| 229 | { |
| 230 | int ret = 0; |
| 231 | pgtable_t pgtable; |
| 232 | |
| 233 | VM_BUG_ON(!PageCompound(page)); |
| 234 | pgtable = pte_alloc_one(mm, haddr); |
| 235 | if (unlikely(!pgtable)) { |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 236 | mem_cgroup_uncharge_page(page); |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 237 | put_page(page); |
| 238 | return VM_FAULT_OOM; |
| 239 | } |
| 240 | |
| 241 | clear_huge_page(page, haddr, HPAGE_PMD_NR); |
| 242 | __SetPageUptodate(page); |
| 243 | |
| 244 | spin_lock(&mm->page_table_lock); |
| 245 | if (unlikely(!pmd_none(*pmd))) { |
| 246 | spin_unlock(&mm->page_table_lock); |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 247 | mem_cgroup_uncharge_page(page); |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 248 | put_page(page); |
| 249 | pte_free(mm, pgtable); |
| 250 | } else { |
| 251 | pmd_t entry; |
| 252 | entry = mk_pmd(page, vma->vm_page_prot); |
| 253 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); |
| 254 | entry = pmd_mkhuge(entry); |
| 255 | /* |
| 256 | * The spinlocking to take the lru_lock inside |
| 257 | * page_add_new_anon_rmap() acts as a full memory |
| 258 | * barrier to be sure clear_huge_page writes become |
| 259 | * visible after the set_pmd_at() write. |
| 260 | */ |
| 261 | page_add_new_anon_rmap(page, vma, haddr); |
| 262 | set_pmd_at(mm, haddr, pmd, entry); |
| 263 | prepare_pmd_huge_pte(pgtable, mm); |
| 264 | add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); |
| 265 | spin_unlock(&mm->page_table_lock); |
| 266 | } |
| 267 | |
| 268 | return ret; |
| 269 | } |
| 270 | |
| 271 | static inline struct page *alloc_hugepage(int defrag) |
| 272 | { |
| 273 | return alloc_pages(GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT), |
| 274 | HPAGE_PMD_ORDER); |
| 275 | } |
| 276 | |
| 277 | int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, |
| 278 | unsigned long address, pmd_t *pmd, |
| 279 | unsigned int flags) |
| 280 | { |
| 281 | struct page *page; |
| 282 | unsigned long haddr = address & HPAGE_PMD_MASK; |
| 283 | pte_t *pte; |
| 284 | |
| 285 | if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { |
| 286 | if (unlikely(anon_vma_prepare(vma))) |
| 287 | return VM_FAULT_OOM; |
| 288 | page = alloc_hugepage(transparent_hugepage_defrag(vma)); |
| 289 | if (unlikely(!page)) |
| 290 | goto out; |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 291 | if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { |
| 292 | put_page(page); |
| 293 | goto out; |
| 294 | } |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 295 | |
| 296 | return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page); |
| 297 | } |
| 298 | out: |
| 299 | /* |
| 300 | * Use __pte_alloc instead of pte_alloc_map, because we can't |
| 301 | * run pte_offset_map on the pmd, if an huge pmd could |
| 302 | * materialize from under us from a different thread. |
| 303 | */ |
| 304 | if (unlikely(__pte_alloc(mm, vma, pmd, address))) |
| 305 | return VM_FAULT_OOM; |
| 306 | /* if an huge pmd materialized from under us just retry later */ |
| 307 | if (unlikely(pmd_trans_huge(*pmd))) |
| 308 | return 0; |
| 309 | /* |
| 310 | * A regular pmd is established and it can't morph into a huge pmd |
| 311 | * from under us anymore at this point because we hold the mmap_sem |
| 312 | * read mode and khugepaged takes it in write mode. So now it's |
| 313 | * safe to run pte_offset_map(). |
| 314 | */ |
| 315 | pte = pte_offset_map(pmd, address); |
| 316 | return handle_pte_fault(mm, vma, address, pte, pmd, flags); |
| 317 | } |
| 318 | |
| 319 | int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, |
| 320 | pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, |
| 321 | struct vm_area_struct *vma) |
| 322 | { |
| 323 | struct page *src_page; |
| 324 | pmd_t pmd; |
| 325 | pgtable_t pgtable; |
| 326 | int ret; |
| 327 | |
| 328 | ret = -ENOMEM; |
| 329 | pgtable = pte_alloc_one(dst_mm, addr); |
| 330 | if (unlikely(!pgtable)) |
| 331 | goto out; |
| 332 | |
| 333 | spin_lock(&dst_mm->page_table_lock); |
| 334 | spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); |
| 335 | |
| 336 | ret = -EAGAIN; |
| 337 | pmd = *src_pmd; |
| 338 | if (unlikely(!pmd_trans_huge(pmd))) { |
| 339 | pte_free(dst_mm, pgtable); |
| 340 | goto out_unlock; |
| 341 | } |
| 342 | if (unlikely(pmd_trans_splitting(pmd))) { |
| 343 | /* split huge page running from under us */ |
| 344 | spin_unlock(&src_mm->page_table_lock); |
| 345 | spin_unlock(&dst_mm->page_table_lock); |
| 346 | pte_free(dst_mm, pgtable); |
| 347 | |
| 348 | wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ |
| 349 | goto out; |
| 350 | } |
| 351 | src_page = pmd_page(pmd); |
| 352 | VM_BUG_ON(!PageHead(src_page)); |
| 353 | get_page(src_page); |
| 354 | page_dup_rmap(src_page); |
| 355 | add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); |
| 356 | |
| 357 | pmdp_set_wrprotect(src_mm, addr, src_pmd); |
| 358 | pmd = pmd_mkold(pmd_wrprotect(pmd)); |
| 359 | set_pmd_at(dst_mm, addr, dst_pmd, pmd); |
| 360 | prepare_pmd_huge_pte(pgtable, dst_mm); |
| 361 | |
| 362 | ret = 0; |
| 363 | out_unlock: |
| 364 | spin_unlock(&src_mm->page_table_lock); |
| 365 | spin_unlock(&dst_mm->page_table_lock); |
| 366 | out: |
| 367 | return ret; |
| 368 | } |
| 369 | |
| 370 | /* no "address" argument so destroys page coloring of some arch */ |
| 371 | pgtable_t get_pmd_huge_pte(struct mm_struct *mm) |
| 372 | { |
| 373 | pgtable_t pgtable; |
| 374 | |
| 375 | assert_spin_locked(&mm->page_table_lock); |
| 376 | |
| 377 | /* FIFO */ |
| 378 | pgtable = mm->pmd_huge_pte; |
| 379 | if (list_empty(&pgtable->lru)) |
| 380 | mm->pmd_huge_pte = NULL; |
| 381 | else { |
| 382 | mm->pmd_huge_pte = list_entry(pgtable->lru.next, |
| 383 | struct page, lru); |
| 384 | list_del(&pgtable->lru); |
| 385 | } |
| 386 | return pgtable; |
| 387 | } |
| 388 | |
| 389 | static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, |
| 390 | struct vm_area_struct *vma, |
| 391 | unsigned long address, |
| 392 | pmd_t *pmd, pmd_t orig_pmd, |
| 393 | struct page *page, |
| 394 | unsigned long haddr) |
| 395 | { |
| 396 | pgtable_t pgtable; |
| 397 | pmd_t _pmd; |
| 398 | int ret = 0, i; |
| 399 | struct page **pages; |
| 400 | |
| 401 | pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, |
| 402 | GFP_KERNEL); |
| 403 | if (unlikely(!pages)) { |
| 404 | ret |= VM_FAULT_OOM; |
| 405 | goto out; |
| 406 | } |
| 407 | |
| 408 | for (i = 0; i < HPAGE_PMD_NR; i++) { |
| 409 | pages[i] = alloc_page_vma(GFP_HIGHUSER_MOVABLE, |
| 410 | vma, address); |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 411 | if (unlikely(!pages[i] || |
| 412 | mem_cgroup_newpage_charge(pages[i], mm, |
| 413 | GFP_KERNEL))) { |
| 414 | if (pages[i]) |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 415 | put_page(pages[i]); |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 416 | mem_cgroup_uncharge_start(); |
| 417 | while (--i >= 0) { |
| 418 | mem_cgroup_uncharge_page(pages[i]); |
| 419 | put_page(pages[i]); |
| 420 | } |
| 421 | mem_cgroup_uncharge_end(); |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 422 | kfree(pages); |
| 423 | ret |= VM_FAULT_OOM; |
| 424 | goto out; |
| 425 | } |
| 426 | } |
| 427 | |
| 428 | for (i = 0; i < HPAGE_PMD_NR; i++) { |
| 429 | copy_user_highpage(pages[i], page + i, |
| 430 | haddr + PAGE_SHIFT*i, vma); |
| 431 | __SetPageUptodate(pages[i]); |
| 432 | cond_resched(); |
| 433 | } |
| 434 | |
| 435 | spin_lock(&mm->page_table_lock); |
| 436 | if (unlikely(!pmd_same(*pmd, orig_pmd))) |
| 437 | goto out_free_pages; |
| 438 | VM_BUG_ON(!PageHead(page)); |
| 439 | |
| 440 | pmdp_clear_flush_notify(vma, haddr, pmd); |
| 441 | /* leave pmd empty until pte is filled */ |
| 442 | |
| 443 | pgtable = get_pmd_huge_pte(mm); |
| 444 | pmd_populate(mm, &_pmd, pgtable); |
| 445 | |
| 446 | for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { |
| 447 | pte_t *pte, entry; |
| 448 | entry = mk_pte(pages[i], vma->vm_page_prot); |
| 449 | entry = maybe_mkwrite(pte_mkdirty(entry), vma); |
| 450 | page_add_new_anon_rmap(pages[i], vma, haddr); |
| 451 | pte = pte_offset_map(&_pmd, haddr); |
| 452 | VM_BUG_ON(!pte_none(*pte)); |
| 453 | set_pte_at(mm, haddr, pte, entry); |
| 454 | pte_unmap(pte); |
| 455 | } |
| 456 | kfree(pages); |
| 457 | |
| 458 | mm->nr_ptes++; |
| 459 | smp_wmb(); /* make pte visible before pmd */ |
| 460 | pmd_populate(mm, pmd, pgtable); |
| 461 | page_remove_rmap(page); |
| 462 | spin_unlock(&mm->page_table_lock); |
| 463 | |
| 464 | ret |= VM_FAULT_WRITE; |
| 465 | put_page(page); |
| 466 | |
| 467 | out: |
| 468 | return ret; |
| 469 | |
| 470 | out_free_pages: |
| 471 | spin_unlock(&mm->page_table_lock); |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 472 | mem_cgroup_uncharge_start(); |
| 473 | for (i = 0; i < HPAGE_PMD_NR; i++) { |
| 474 | mem_cgroup_uncharge_page(pages[i]); |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 475 | put_page(pages[i]); |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 476 | } |
| 477 | mem_cgroup_uncharge_end(); |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 478 | kfree(pages); |
| 479 | goto out; |
| 480 | } |
| 481 | |
| 482 | int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, |
| 483 | unsigned long address, pmd_t *pmd, pmd_t orig_pmd) |
| 484 | { |
| 485 | int ret = 0; |
| 486 | struct page *page, *new_page; |
| 487 | unsigned long haddr; |
| 488 | |
| 489 | VM_BUG_ON(!vma->anon_vma); |
| 490 | spin_lock(&mm->page_table_lock); |
| 491 | if (unlikely(!pmd_same(*pmd, orig_pmd))) |
| 492 | goto out_unlock; |
| 493 | |
| 494 | page = pmd_page(orig_pmd); |
| 495 | VM_BUG_ON(!PageCompound(page) || !PageHead(page)); |
| 496 | haddr = address & HPAGE_PMD_MASK; |
| 497 | if (page_mapcount(page) == 1) { |
| 498 | pmd_t entry; |
| 499 | entry = pmd_mkyoung(orig_pmd); |
| 500 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); |
| 501 | if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) |
| 502 | update_mmu_cache(vma, address, entry); |
| 503 | ret |= VM_FAULT_WRITE; |
| 504 | goto out_unlock; |
| 505 | } |
| 506 | get_page(page); |
| 507 | spin_unlock(&mm->page_table_lock); |
| 508 | |
| 509 | if (transparent_hugepage_enabled(vma) && |
| 510 | !transparent_hugepage_debug_cow()) |
| 511 | new_page = alloc_hugepage(transparent_hugepage_defrag(vma)); |
| 512 | else |
| 513 | new_page = NULL; |
| 514 | |
| 515 | if (unlikely(!new_page)) { |
| 516 | ret = do_huge_pmd_wp_page_fallback(mm, vma, address, |
| 517 | pmd, orig_pmd, page, haddr); |
| 518 | put_page(page); |
| 519 | goto out; |
| 520 | } |
| 521 | |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 522 | if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { |
| 523 | put_page(new_page); |
| 524 | put_page(page); |
| 525 | ret |= VM_FAULT_OOM; |
| 526 | goto out; |
| 527 | } |
| 528 | |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 529 | copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); |
| 530 | __SetPageUptodate(new_page); |
| 531 | |
| 532 | spin_lock(&mm->page_table_lock); |
| 533 | put_page(page); |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 534 | if (unlikely(!pmd_same(*pmd, orig_pmd))) { |
| 535 | mem_cgroup_uncharge_page(new_page); |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 536 | put_page(new_page); |
Andrea Arcangeli | b9bbfbe | 2011-01-13 15:46:57 -0800 | [diff] [blame] | 537 | } else { |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 538 | pmd_t entry; |
| 539 | VM_BUG_ON(!PageHead(page)); |
| 540 | entry = mk_pmd(new_page, vma->vm_page_prot); |
| 541 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); |
| 542 | entry = pmd_mkhuge(entry); |
| 543 | pmdp_clear_flush_notify(vma, haddr, pmd); |
| 544 | page_add_new_anon_rmap(new_page, vma, haddr); |
| 545 | set_pmd_at(mm, haddr, pmd, entry); |
| 546 | update_mmu_cache(vma, address, entry); |
| 547 | page_remove_rmap(page); |
| 548 | put_page(page); |
| 549 | ret |= VM_FAULT_WRITE; |
| 550 | } |
| 551 | out_unlock: |
| 552 | spin_unlock(&mm->page_table_lock); |
| 553 | out: |
| 554 | return ret; |
| 555 | } |
| 556 | |
| 557 | struct page *follow_trans_huge_pmd(struct mm_struct *mm, |
| 558 | unsigned long addr, |
| 559 | pmd_t *pmd, |
| 560 | unsigned int flags) |
| 561 | { |
| 562 | struct page *page = NULL; |
| 563 | |
| 564 | assert_spin_locked(&mm->page_table_lock); |
| 565 | |
| 566 | if (flags & FOLL_WRITE && !pmd_write(*pmd)) |
| 567 | goto out; |
| 568 | |
| 569 | page = pmd_page(*pmd); |
| 570 | VM_BUG_ON(!PageHead(page)); |
| 571 | if (flags & FOLL_TOUCH) { |
| 572 | pmd_t _pmd; |
| 573 | /* |
| 574 | * We should set the dirty bit only for FOLL_WRITE but |
| 575 | * for now the dirty bit in the pmd is meaningless. |
| 576 | * And if the dirty bit will become meaningful and |
| 577 | * we'll only set it with FOLL_WRITE, an atomic |
| 578 | * set_bit will be required on the pmd to set the |
| 579 | * young bit, instead of the current set_pmd_at. |
| 580 | */ |
| 581 | _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); |
| 582 | set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); |
| 583 | } |
| 584 | page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; |
| 585 | VM_BUG_ON(!PageCompound(page)); |
| 586 | if (flags & FOLL_GET) |
| 587 | get_page(page); |
| 588 | |
| 589 | out: |
| 590 | return page; |
| 591 | } |
| 592 | |
| 593 | int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, |
| 594 | pmd_t *pmd) |
| 595 | { |
| 596 | int ret = 0; |
| 597 | |
| 598 | spin_lock(&tlb->mm->page_table_lock); |
| 599 | if (likely(pmd_trans_huge(*pmd))) { |
| 600 | if (unlikely(pmd_trans_splitting(*pmd))) { |
| 601 | spin_unlock(&tlb->mm->page_table_lock); |
| 602 | wait_split_huge_page(vma->anon_vma, |
| 603 | pmd); |
| 604 | } else { |
| 605 | struct page *page; |
| 606 | pgtable_t pgtable; |
| 607 | pgtable = get_pmd_huge_pte(tlb->mm); |
| 608 | page = pmd_page(*pmd); |
| 609 | pmd_clear(pmd); |
| 610 | page_remove_rmap(page); |
| 611 | VM_BUG_ON(page_mapcount(page) < 0); |
| 612 | add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); |
| 613 | VM_BUG_ON(!PageHead(page)); |
| 614 | spin_unlock(&tlb->mm->page_table_lock); |
| 615 | tlb_remove_page(tlb, page); |
| 616 | pte_free(tlb->mm, pgtable); |
| 617 | ret = 1; |
| 618 | } |
| 619 | } else |
| 620 | spin_unlock(&tlb->mm->page_table_lock); |
| 621 | |
| 622 | return ret; |
| 623 | } |
| 624 | |
| 625 | pmd_t *page_check_address_pmd(struct page *page, |
| 626 | struct mm_struct *mm, |
| 627 | unsigned long address, |
| 628 | enum page_check_address_pmd_flag flag) |
| 629 | { |
| 630 | pgd_t *pgd; |
| 631 | pud_t *pud; |
| 632 | pmd_t *pmd, *ret = NULL; |
| 633 | |
| 634 | if (address & ~HPAGE_PMD_MASK) |
| 635 | goto out; |
| 636 | |
| 637 | pgd = pgd_offset(mm, address); |
| 638 | if (!pgd_present(*pgd)) |
| 639 | goto out; |
| 640 | |
| 641 | pud = pud_offset(pgd, address); |
| 642 | if (!pud_present(*pud)) |
| 643 | goto out; |
| 644 | |
| 645 | pmd = pmd_offset(pud, address); |
| 646 | if (pmd_none(*pmd)) |
| 647 | goto out; |
| 648 | if (pmd_page(*pmd) != page) |
| 649 | goto out; |
| 650 | VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && |
| 651 | pmd_trans_splitting(*pmd)); |
| 652 | if (pmd_trans_huge(*pmd)) { |
| 653 | VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && |
| 654 | !pmd_trans_splitting(*pmd)); |
| 655 | ret = pmd; |
| 656 | } |
| 657 | out: |
| 658 | return ret; |
| 659 | } |
| 660 | |
| 661 | static int __split_huge_page_splitting(struct page *page, |
| 662 | struct vm_area_struct *vma, |
| 663 | unsigned long address) |
| 664 | { |
| 665 | struct mm_struct *mm = vma->vm_mm; |
| 666 | pmd_t *pmd; |
| 667 | int ret = 0; |
| 668 | |
| 669 | spin_lock(&mm->page_table_lock); |
| 670 | pmd = page_check_address_pmd(page, mm, address, |
| 671 | PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); |
| 672 | if (pmd) { |
| 673 | /* |
| 674 | * We can't temporarily set the pmd to null in order |
| 675 | * to split it, the pmd must remain marked huge at all |
| 676 | * times or the VM won't take the pmd_trans_huge paths |
| 677 | * and it won't wait on the anon_vma->root->lock to |
| 678 | * serialize against split_huge_page*. |
| 679 | */ |
| 680 | pmdp_splitting_flush_notify(vma, address, pmd); |
| 681 | ret = 1; |
| 682 | } |
| 683 | spin_unlock(&mm->page_table_lock); |
| 684 | |
| 685 | return ret; |
| 686 | } |
| 687 | |
| 688 | static void __split_huge_page_refcount(struct page *page) |
| 689 | { |
| 690 | int i; |
| 691 | unsigned long head_index = page->index; |
| 692 | struct zone *zone = page_zone(page); |
| 693 | |
| 694 | /* prevent PageLRU to go away from under us, and freeze lru stats */ |
| 695 | spin_lock_irq(&zone->lru_lock); |
| 696 | compound_lock(page); |
| 697 | |
| 698 | for (i = 1; i < HPAGE_PMD_NR; i++) { |
| 699 | struct page *page_tail = page + i; |
| 700 | |
| 701 | /* tail_page->_count cannot change */ |
| 702 | atomic_sub(atomic_read(&page_tail->_count), &page->_count); |
| 703 | BUG_ON(page_count(page) <= 0); |
| 704 | atomic_add(page_mapcount(page) + 1, &page_tail->_count); |
| 705 | BUG_ON(atomic_read(&page_tail->_count) <= 0); |
| 706 | |
| 707 | /* after clearing PageTail the gup refcount can be released */ |
| 708 | smp_mb(); |
| 709 | |
| 710 | page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; |
| 711 | page_tail->flags |= (page->flags & |
| 712 | ((1L << PG_referenced) | |
| 713 | (1L << PG_swapbacked) | |
| 714 | (1L << PG_mlocked) | |
| 715 | (1L << PG_uptodate))); |
| 716 | page_tail->flags |= (1L << PG_dirty); |
| 717 | |
| 718 | /* |
| 719 | * 1) clear PageTail before overwriting first_page |
| 720 | * 2) clear PageTail before clearing PageHead for VM_BUG_ON |
| 721 | */ |
| 722 | smp_wmb(); |
| 723 | |
| 724 | /* |
| 725 | * __split_huge_page_splitting() already set the |
| 726 | * splitting bit in all pmd that could map this |
| 727 | * hugepage, that will ensure no CPU can alter the |
| 728 | * mapcount on the head page. The mapcount is only |
| 729 | * accounted in the head page and it has to be |
| 730 | * transferred to all tail pages in the below code. So |
| 731 | * for this code to be safe, the split the mapcount |
| 732 | * can't change. But that doesn't mean userland can't |
| 733 | * keep changing and reading the page contents while |
| 734 | * we transfer the mapcount, so the pmd splitting |
| 735 | * status is achieved setting a reserved bit in the |
| 736 | * pmd, not by clearing the present bit. |
| 737 | */ |
| 738 | BUG_ON(page_mapcount(page_tail)); |
| 739 | page_tail->_mapcount = page->_mapcount; |
| 740 | |
| 741 | BUG_ON(page_tail->mapping); |
| 742 | page_tail->mapping = page->mapping; |
| 743 | |
| 744 | page_tail->index = ++head_index; |
| 745 | |
| 746 | BUG_ON(!PageAnon(page_tail)); |
| 747 | BUG_ON(!PageUptodate(page_tail)); |
| 748 | BUG_ON(!PageDirty(page_tail)); |
| 749 | BUG_ON(!PageSwapBacked(page_tail)); |
| 750 | |
| 751 | lru_add_page_tail(zone, page, page_tail); |
| 752 | } |
| 753 | |
Andrea Arcangeli | 7913417 | 2011-01-13 15:46:58 -0800 | [diff] [blame^] | 754 | __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); |
| 755 | __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); |
| 756 | |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 757 | ClearPageCompound(page); |
| 758 | compound_unlock(page); |
| 759 | spin_unlock_irq(&zone->lru_lock); |
| 760 | |
| 761 | for (i = 1; i < HPAGE_PMD_NR; i++) { |
| 762 | struct page *page_tail = page + i; |
| 763 | BUG_ON(page_count(page_tail) <= 0); |
| 764 | /* |
| 765 | * Tail pages may be freed if there wasn't any mapping |
| 766 | * like if add_to_swap() is running on a lru page that |
| 767 | * had its mapping zapped. And freeing these pages |
| 768 | * requires taking the lru_lock so we do the put_page |
| 769 | * of the tail pages after the split is complete. |
| 770 | */ |
| 771 | put_page(page_tail); |
| 772 | } |
| 773 | |
| 774 | /* |
| 775 | * Only the head page (now become a regular page) is required |
| 776 | * to be pinned by the caller. |
| 777 | */ |
| 778 | BUG_ON(page_count(page) <= 0); |
| 779 | } |
| 780 | |
| 781 | static int __split_huge_page_map(struct page *page, |
| 782 | struct vm_area_struct *vma, |
| 783 | unsigned long address) |
| 784 | { |
| 785 | struct mm_struct *mm = vma->vm_mm; |
| 786 | pmd_t *pmd, _pmd; |
| 787 | int ret = 0, i; |
| 788 | pgtable_t pgtable; |
| 789 | unsigned long haddr; |
| 790 | |
| 791 | spin_lock(&mm->page_table_lock); |
| 792 | pmd = page_check_address_pmd(page, mm, address, |
| 793 | PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); |
| 794 | if (pmd) { |
| 795 | pgtable = get_pmd_huge_pte(mm); |
| 796 | pmd_populate(mm, &_pmd, pgtable); |
| 797 | |
| 798 | for (i = 0, haddr = address; i < HPAGE_PMD_NR; |
| 799 | i++, haddr += PAGE_SIZE) { |
| 800 | pte_t *pte, entry; |
| 801 | BUG_ON(PageCompound(page+i)); |
| 802 | entry = mk_pte(page + i, vma->vm_page_prot); |
| 803 | entry = maybe_mkwrite(pte_mkdirty(entry), vma); |
| 804 | if (!pmd_write(*pmd)) |
| 805 | entry = pte_wrprotect(entry); |
| 806 | else |
| 807 | BUG_ON(page_mapcount(page) != 1); |
| 808 | if (!pmd_young(*pmd)) |
| 809 | entry = pte_mkold(entry); |
| 810 | pte = pte_offset_map(&_pmd, haddr); |
| 811 | BUG_ON(!pte_none(*pte)); |
| 812 | set_pte_at(mm, haddr, pte, entry); |
| 813 | pte_unmap(pte); |
| 814 | } |
| 815 | |
| 816 | mm->nr_ptes++; |
| 817 | smp_wmb(); /* make pte visible before pmd */ |
| 818 | /* |
| 819 | * Up to this point the pmd is present and huge and |
| 820 | * userland has the whole access to the hugepage |
| 821 | * during the split (which happens in place). If we |
| 822 | * overwrite the pmd with the not-huge version |
| 823 | * pointing to the pte here (which of course we could |
| 824 | * if all CPUs were bug free), userland could trigger |
| 825 | * a small page size TLB miss on the small sized TLB |
| 826 | * while the hugepage TLB entry is still established |
| 827 | * in the huge TLB. Some CPU doesn't like that. See |
| 828 | * http://support.amd.com/us/Processor_TechDocs/41322.pdf, |
| 829 | * Erratum 383 on page 93. Intel should be safe but is |
| 830 | * also warns that it's only safe if the permission |
| 831 | * and cache attributes of the two entries loaded in |
| 832 | * the two TLB is identical (which should be the case |
| 833 | * here). But it is generally safer to never allow |
| 834 | * small and huge TLB entries for the same virtual |
| 835 | * address to be loaded simultaneously. So instead of |
| 836 | * doing "pmd_populate(); flush_tlb_range();" we first |
| 837 | * mark the current pmd notpresent (atomically because |
| 838 | * here the pmd_trans_huge and pmd_trans_splitting |
| 839 | * must remain set at all times on the pmd until the |
| 840 | * split is complete for this pmd), then we flush the |
| 841 | * SMP TLB and finally we write the non-huge version |
| 842 | * of the pmd entry with pmd_populate. |
| 843 | */ |
| 844 | set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd)); |
| 845 | flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); |
| 846 | pmd_populate(mm, pmd, pgtable); |
| 847 | ret = 1; |
| 848 | } |
| 849 | spin_unlock(&mm->page_table_lock); |
| 850 | |
| 851 | return ret; |
| 852 | } |
| 853 | |
| 854 | /* must be called with anon_vma->root->lock hold */ |
| 855 | static void __split_huge_page(struct page *page, |
| 856 | struct anon_vma *anon_vma) |
| 857 | { |
| 858 | int mapcount, mapcount2; |
| 859 | struct anon_vma_chain *avc; |
| 860 | |
| 861 | BUG_ON(!PageHead(page)); |
| 862 | BUG_ON(PageTail(page)); |
| 863 | |
| 864 | mapcount = 0; |
| 865 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
| 866 | struct vm_area_struct *vma = avc->vma; |
| 867 | unsigned long addr = vma_address(page, vma); |
| 868 | BUG_ON(is_vma_temporary_stack(vma)); |
| 869 | if (addr == -EFAULT) |
| 870 | continue; |
| 871 | mapcount += __split_huge_page_splitting(page, vma, addr); |
| 872 | } |
Andrea Arcangeli | 05759d3 | 2011-01-13 15:46:53 -0800 | [diff] [blame] | 873 | /* |
| 874 | * It is critical that new vmas are added to the tail of the |
| 875 | * anon_vma list. This guarantes that if copy_huge_pmd() runs |
| 876 | * and establishes a child pmd before |
| 877 | * __split_huge_page_splitting() freezes the parent pmd (so if |
| 878 | * we fail to prevent copy_huge_pmd() from running until the |
| 879 | * whole __split_huge_page() is complete), we will still see |
| 880 | * the newly established pmd of the child later during the |
| 881 | * walk, to be able to set it as pmd_trans_splitting too. |
| 882 | */ |
| 883 | if (mapcount != page_mapcount(page)) |
| 884 | printk(KERN_ERR "mapcount %d page_mapcount %d\n", |
| 885 | mapcount, page_mapcount(page)); |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 886 | BUG_ON(mapcount != page_mapcount(page)); |
| 887 | |
| 888 | __split_huge_page_refcount(page); |
| 889 | |
| 890 | mapcount2 = 0; |
| 891 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
| 892 | struct vm_area_struct *vma = avc->vma; |
| 893 | unsigned long addr = vma_address(page, vma); |
| 894 | BUG_ON(is_vma_temporary_stack(vma)); |
| 895 | if (addr == -EFAULT) |
| 896 | continue; |
| 897 | mapcount2 += __split_huge_page_map(page, vma, addr); |
| 898 | } |
Andrea Arcangeli | 05759d3 | 2011-01-13 15:46:53 -0800 | [diff] [blame] | 899 | if (mapcount != mapcount2) |
| 900 | printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", |
| 901 | mapcount, mapcount2, page_mapcount(page)); |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 902 | BUG_ON(mapcount != mapcount2); |
| 903 | } |
| 904 | |
| 905 | int split_huge_page(struct page *page) |
| 906 | { |
| 907 | struct anon_vma *anon_vma; |
| 908 | int ret = 1; |
| 909 | |
| 910 | BUG_ON(!PageAnon(page)); |
| 911 | anon_vma = page_lock_anon_vma(page); |
| 912 | if (!anon_vma) |
| 913 | goto out; |
| 914 | ret = 0; |
| 915 | if (!PageCompound(page)) |
| 916 | goto out_unlock; |
| 917 | |
| 918 | BUG_ON(!PageSwapBacked(page)); |
| 919 | __split_huge_page(page, anon_vma); |
| 920 | |
| 921 | BUG_ON(PageCompound(page)); |
| 922 | out_unlock: |
| 923 | page_unlock_anon_vma(anon_vma); |
| 924 | out: |
| 925 | return ret; |
| 926 | } |
| 927 | |
Andrea Arcangeli | 0af4e98 | 2011-01-13 15:46:55 -0800 | [diff] [blame] | 928 | int hugepage_madvise(unsigned long *vm_flags) |
| 929 | { |
| 930 | /* |
| 931 | * Be somewhat over-protective like KSM for now! |
| 932 | */ |
| 933 | if (*vm_flags & (VM_HUGEPAGE | VM_SHARED | VM_MAYSHARE | |
| 934 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | |
| 935 | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | |
| 936 | VM_MIXEDMAP | VM_SAO)) |
| 937 | return -EINVAL; |
| 938 | |
| 939 | *vm_flags |= VM_HUGEPAGE; |
| 940 | |
| 941 | return 0; |
| 942 | } |
| 943 | |
Andrea Arcangeli | 71e3aac | 2011-01-13 15:46:52 -0800 | [diff] [blame] | 944 | void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) |
| 945 | { |
| 946 | struct page *page; |
| 947 | |
| 948 | spin_lock(&mm->page_table_lock); |
| 949 | if (unlikely(!pmd_trans_huge(*pmd))) { |
| 950 | spin_unlock(&mm->page_table_lock); |
| 951 | return; |
| 952 | } |
| 953 | page = pmd_page(*pmd); |
| 954 | VM_BUG_ON(!page_count(page)); |
| 955 | get_page(page); |
| 956 | spin_unlock(&mm->page_table_lock); |
| 957 | |
| 958 | split_huge_page(page); |
| 959 | |
| 960 | put_page(page); |
| 961 | BUG_ON(pmd_trans_huge(*pmd)); |
| 962 | } |