mm/mremap.c

   1 /*
   2  *      mm/mremap.c
   3  *
   4  *      (C) Copyright 1996 Linus Torvalds
   5  *
   6  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
   7  *      (C) Copyright 2002 Red Hat Inc, All Rights Reserved
   8  */
   9
  10 #include <linux/mm.h>
  11 #include <linux/hugetlb.h>
  12 #include <linux/shm.h>
  13 #include <linux/ksm.h>
  14 #include <linux/mman.h>
  15 #include <linux/swap.h>
  16 #include <linux/capability.h>
  17 #include <linux/fs.h>
  18 #include <linux/swapops.h>
  19 #include <linux/highmem.h>
  20 #include <linux/security.h>
  21 #include <linux/syscalls.h>
  22 #include <linux/mmu_notifier.h>
  23 #include <linux/uaccess.h>
  24 #include <linux/mm-arch-hooks.h>
  25 #include <linux/userfaultfd_k.h>
  26
  27 #include <asm/cacheflush.h>
  28 #include <asm/tlbflush.h>
  29
  30 #include "internal.h"
  31
  32 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  33 {
  34         pgd_t *pgd;
  35         p4d_t *p4d;
  36         pud_t *pud;
  37         pmd_t *pmd;
  38
  39         pgd = pgd_offset(mm, addr);
  40         if (pgd_none_or_clear_bad(pgd))
  41                 return NULL;
  42
  43         p4d = p4d_offset(pgd, addr);
  44         if (p4d_none_or_clear_bad(p4d))
  45                 return NULL;
  46
  47         pud = pud_offset(p4d, addr);
  48         if (pud_none_or_clear_bad(pud))
  49                 return NULL;
  50
  51         pmd = pmd_offset(pud, addr);
  52         if (pmd_none(*pmd))
  53                 return NULL;
  54
  55         return pmd;
  56 }
  57
  58 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
  59                             unsigned long addr)
  60 {
  61         pgd_t *pgd;
  62         p4d_t *p4d;
  63         pud_t *pud;
  64         pmd_t *pmd;
  65
  66         pgd = pgd_offset(mm, addr);
  67         p4d = p4d_alloc(mm, pgd, addr);
  68         if (!p4d)
  69                 return NULL;
  70         pud = pud_alloc(mm, p4d, addr);
  71         if (!pud)
  72                 return NULL;
  73
  74         pmd = pmd_alloc(mm, pud, addr);
  75         if (!pmd)
  76                 return NULL;
  77
  78         VM_BUG_ON(pmd_trans_huge(*pmd));
  79
  80         return pmd;
  81 }
  82
  83 static void take_rmap_locks(struct vm_area_struct *vma)
  84 {
  85         if (vma->vm_file)
  86                 i_mmap_lock_write(vma->vm_file->f_mapping);
  87         if (vma->anon_vma)
  88                 anon_vma_lock_write(vma->anon_vma);
  89 }
  90
  91 static void drop_rmap_locks(struct vm_area_struct *vma)
  92 {
  93         if (vma->anon_vma)
  94                 anon_vma_unlock_write(vma->anon_vma);
  95         if (vma->vm_file)
  96                 i_mmap_unlock_write(vma->vm_file->f_mapping);
  97 }
  98
  99 static pte_t move_soft_dirty_pte(pte_t pte)
 100 {
 101         /*
 102          * Set soft dirty bit so we can notice
 103          * in userspace the ptes were moved.
 104          */
 105 #ifdef CONFIG_MEM_SOFT_DIRTY
 106         if (pte_present(pte))
 107                 pte = pte_mksoft_dirty(pte);
 108         else if (is_swap_pte(pte))
 109                 pte = pte_swp_mksoft_dirty(pte);
 110 #endif
 111         return pte;
 112 }
 113
 114 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 115                 unsigned long old_addr, unsigned long old_end,
 116                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
 117                 unsigned long new_addr, bool need_rmap_locks, bool *need_flush)
 118 {
 119         struct mm_struct *mm = vma->vm_mm;
 120         pte_t *old_pte, *new_pte, pte;
 121         spinlock_t *old_ptl, *new_ptl;
 122         bool force_flush = false;
 123         unsigned long len = old_end - old_addr;
 124
 125         /*
 126          * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
 127          * locks to ensure that rmap will always observe either the old or the
 128          * new ptes. This is the easiest way to avoid races with
 129          * truncate_pagecache(), page migration, etc...
 130          *
 131          * When need_rmap_locks is false, we use other ways to avoid
 132          * such races:
 133          *
 134          * - During exec() shift_arg_pages(), we use a specially tagged vma
 135          *   which rmap call sites look for using is_vma_temporary_stack().
 136          *
 137          * - During mremap(), new_vma is often known to be placed after vma
 138          *   in rmap traversal order. This ensures rmap will always observe
 139          *   either the old pte, or the new pte, or both (the page table locks
 140          *   serialize access to individual ptes, but only rmap traversal
 141          *   order guarantees that we won't miss both the old and new ptes).
 142          */
 143         if (need_rmap_locks)
 144                 take_rmap_locks(vma);
 145
 146         /*
 147          * We don't have to worry about the ordering of src and dst
 148          * pte locks because exclusive mmap_sem prevents deadlock.
 149          */
 150         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
 151         new_pte = pte_offset_map(new_pmd, new_addr);
 152         new_ptl = pte_lockptr(mm, new_pmd);
 153         if (new_ptl != old_ptl)
 154                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 155         flush_tlb_batched_pending(vma->vm_mm);
 156         arch_enter_lazy_mmu_mode();
 157
 158         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 159                                    new_pte++, new_addr += PAGE_SIZE) {
 160                 if (pte_none(*old_pte))
 161                         continue;
 162
 163                 pte = ptep_get_and_clear(mm, old_addr, old_pte);
 164                 /*
 165                  * If we are remapping a dirty PTE, make sure
 166                  * to flush TLB before we drop the PTL for the
 167                  * old PTE or we may race with page_mkclean().
 168                  *
 169                  * This check has to be done after we removed the
 170                  * old PTE from page tables or another thread may
 171                  * dirty it after the check and before the removal.
 172                  */
 173                 if (pte_present(pte) && pte_dirty(pte))
 174                         force_flush = true;
 175                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 176                 pte = move_soft_dirty_pte(pte);
 177                 set_pte_at(mm, new_addr, new_pte, pte);
 178         }
 179
 180         arch_leave_lazy_mmu_mode();
 181         if (new_ptl != old_ptl)
 182                 spin_unlock(new_ptl);
 183         pte_unmap(new_pte - 1);
 184         if (force_flush)
 185                 flush_tlb_range(vma, old_end - len, old_end);
 186         else
 187                 *need_flush = true;
 188         pte_unmap_unlock(old_pte - 1, old_ptl);
 189         if (need_rmap_locks)
 190                 drop_rmap_locks(vma);
 191 }
 192
 193 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 194
 195 unsigned long move_page_tables(struct vm_area_struct *vma,
 196                 unsigned long old_addr, struct vm_area_struct *new_vma,
 197                 unsigned long new_addr, unsigned long len,
 198                 bool need_rmap_locks)
 199 {
 200         unsigned long extent, next, old_end;
 201         pmd_t *old_pmd, *new_pmd;
 202         bool need_flush = false;
 203         unsigned long mmun_start;       /* For mmu_notifiers */
 204         unsigned long mmun_end;         /* For mmu_notifiers */
 205
 206         old_end = old_addr + len;
 207         flush_cache_range(vma, old_addr, old_end);
 208
 209         mmun_start = old_addr;
 210         mmun_end   = old_end;
 211         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
 212
 213         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 214                 cond_resched();
 215                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 216                 /* even if next overflowed, extent below will be ok */
 217                 extent = next - old_addr;
 218                 if (extent > old_end - old_addr)
 219                         extent = old_end - old_addr;
 220                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 221                 if (!old_pmd)
 222                         continue;
 223                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
 224                 if (!new_pmd)
 225                         break;
 226                 if (pmd_trans_huge(*old_pmd)) {
 227                         if (extent == HPAGE_PMD_SIZE) {
 228                                 bool moved;
 229                                 /* See comment in move_ptes() */
 230                                 if (need_rmap_locks)
 231                                         take_rmap_locks(vma);
 232                                 moved = move_huge_pmd(vma, old_addr, new_addr,
 233                                                     old_end, old_pmd, new_pmd,
 234                                                     &need_flush);
 235                                 if (need_rmap_locks)
 236                                         drop_rmap_locks(vma);
 237                                 if (moved)
 238                                         continue;
 239                         }
 240                         split_huge_pmd(vma, old_pmd, old_addr);
 241                         if (pmd_trans_unstable(old_pmd))
 242                                 continue;
 243                 }
 244                 if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr))
 245                         break;
 246                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 247                 if (extent > next - new_addr)
 248                         extent = next - new_addr;
 249                 if (extent > LATENCY_LIMIT)
 250                         extent = LATENCY_LIMIT;
 251                 move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
 252                           new_pmd, new_addr, need_rmap_locks, &need_flush);
 253         }
 254         if (need_flush)
 255                 flush_tlb_range(vma, old_end-len, old_addr);
 256
 257         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
 258
 259         return len + old_addr - old_end;        /* how much done */
 260 }
 261
 262 static unsigned long move_vma(struct vm_area_struct *vma,
 263                 unsigned long old_addr, unsigned long old_len,
 264                 unsigned long new_len, unsigned long new_addr,
 265                 bool *locked, struct vm_userfaultfd_ctx *uf,
 266                 struct list_head *uf_unmap)
 267 {
 268         struct mm_struct *mm = vma->vm_mm;
 269         struct vm_area_struct *new_vma;
 270         unsigned long vm_flags = vma->vm_flags;
 271         unsigned long new_pgoff;
 272         unsigned long moved_len;
 273         unsigned long excess = 0;
 274         unsigned long hiwater_vm;
 275         int split = 0;
 276         int err;
 277         bool need_rmap_locks;
 278
 279         /*
 280          * We'd prefer to avoid failure later on in do_munmap:
 281          * which may split one vma into three before unmapping.
 282          */
 283         if (mm->map_count >= sysctl_max_map_count - 3)
 284                 return -ENOMEM;
 285
 286         /*
 287          * Advise KSM to break any KSM pages in the area to be moved:
 288          * it would be confusing if they were to turn up at the new
 289          * location, where they happen to coincide with different KSM
 290          * pages recently unmapped.  But leave vma->vm_flags as it was,
 291          * so KSM can come around to merge on vma and new_vma afterwards.
 292          */
 293         err = ksm_madvise(vma, old_addr, old_addr + old_len,
 294                                                 MADV_UNMERGEABLE, &vm_flags);
 295         if (err)
 296                 return err;
 297
 298         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 299         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
 300                            &need_rmap_locks);
 301         if (!new_vma)
 302                 return -ENOMEM;
 303
 304         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
 305                                      need_rmap_locks);
 306         if (moved_len < old_len) {
 307                 err = -ENOMEM;
 308         } else if (vma->vm_ops && vma->vm_ops->mremap) {
 309                 err = vma->vm_ops->mremap(new_vma);
 310         }
 311
 312         if (unlikely(err)) {
 313                 /*
 314                  * On error, move entries back from new area to old,
 315                  * which will succeed since page tables still there,
 316                  * and then proceed to unmap new area instead of old.
 317                  */
 318                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
 319                                  true);
 320                 vma = new_vma;
 321                 old_len = new_len;
 322                 old_addr = new_addr;
 323                 new_addr = err;
 324         } else {
 325                 mremap_userfaultfd_prep(new_vma, uf);
 326                 arch_remap(mm, old_addr, old_addr + old_len,
 327                            new_addr, new_addr + new_len);
 328         }
 329
 330         /* Conceal VM_ACCOUNT so old reservation is not undone */
 331         if (vm_flags & VM_ACCOUNT) {
 332                 vma->vm_flags &= ~VM_ACCOUNT;
 333                 excess = vma->vm_end - vma->vm_start - old_len;
 334                 if (old_addr > vma->vm_start &&
 335                     old_addr + old_len < vma->vm_end)
 336                         split = 1;
 337         }
 338
 339         /*
 340          * If we failed to move page tables we still do total_vm increment
 341          * since do_munmap() will decrement it by old_len == new_len.
 342          *
 343          * Since total_vm is about to be raised artificially high for a
 344          * moment, we need to restore high watermark afterwards: if stats
 345          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 346          * If this were a serious issue, we'd add a flag to do_munmap().
 347          */
 348         hiwater_vm = mm->hiwater_vm;
 349         vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
 350
 351         /* Tell pfnmap has moved from this vma */
 352         if (unlikely(vma->vm_flags & VM_PFNMAP))
 353                 untrack_pfn_moved(vma);
 354
 355         if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
 356                 /* OOM: unable to split vma, just get accounts right */
 357                 vm_unacct_memory(excess >> PAGE_SHIFT);
 358                 excess = 0;
 359         }
 360         mm->hiwater_vm = hiwater_vm;
 361
 362         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 363         if (excess) {
 364                 vma->vm_flags |= VM_ACCOUNT;
 365                 if (split)
 366                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 367         }
 368
 369         if (vm_flags & VM_LOCKED) {
 370                 mm->locked_vm += new_len >> PAGE_SHIFT;
 371                 *locked = true;
 372         }
 373
 374         return new_addr;
 375 }
 376
 377 static struct vm_area_struct *vma_to_resize(unsigned long addr,
 378         unsigned long old_len, unsigned long new_len, unsigned long *p)
 379 {
 380         struct mm_struct *mm = current->mm;
 381         struct vm_area_struct *vma = find_vma(mm, addr);
 382         unsigned long pgoff;
 383
 384         if (!vma || vma->vm_start > addr)
 385                 return ERR_PTR(-EFAULT);
 386
 387         if (is_vm_hugetlb_page(vma))
 388                 return ERR_PTR(-EINVAL);
 389
 390         /* We can't remap across vm area boundaries */
 391         if (old_len > vma->vm_end - addr)
 392                 return ERR_PTR(-EFAULT);
 393
 394         if (new_len == old_len)
 395                 return vma;
 396
 397         /* Need to be careful about a growing mapping */
 398         pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
 399         pgoff += vma->vm_pgoff;
 400         if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
 401                 return ERR_PTR(-EINVAL);
 402
 403         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
 404                 return ERR_PTR(-EFAULT);
 405
 406         if (vma->vm_flags & VM_LOCKED) {
 407                 unsigned long locked, lock_limit;
 408                 locked = mm->locked_vm << PAGE_SHIFT;
 409                 lock_limit = rlimit(RLIMIT_MEMLOCK);
 410                 locked += new_len - old_len;
 411                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 412                         return ERR_PTR(-EAGAIN);
 413         }
 414
 415         if (!may_expand_vm(mm, vma->vm_flags,
 416                                 (new_len - old_len) >> PAGE_SHIFT))
 417                 return ERR_PTR(-ENOMEM);
 418
 419         if (vma->vm_flags & VM_ACCOUNT) {
 420                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
 421                 if (security_vm_enough_memory_mm(mm, charged))
 422                         return ERR_PTR(-ENOMEM);
 423                 *p = charged;
 424         }
 425
 426         return vma;
 427 }
 428
 429 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 430                 unsigned long new_addr, unsigned long new_len, bool *locked,
 431                 struct vm_userfaultfd_ctx *uf,
 432                 struct list_head *uf_unmap_early,
 433                 struct list_head *uf_unmap)
 434 {
 435         struct mm_struct *mm = current->mm;
 436         struct vm_area_struct *vma;
 437         unsigned long ret = -EINVAL;
 438         unsigned long charged = 0;
 439         unsigned long map_flags;
 440
 441         if (offset_in_page(new_addr))
 442                 goto out;
 443
 444         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 445                 goto out;
 446
 447         /* Ensure the old/new locations do not overlap */
 448         if (addr + old_len > new_addr && new_addr + new_len > addr)
 449                 goto out;
 450
 451         ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
 452         if (ret)
 453                 goto out;
 454
 455         if (old_len >= new_len) {
 456                 ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
 457                 if (ret && old_len != new_len)
 458                         goto out;
 459                 old_len = new_len;
 460         }
 461
 462         vma = vma_to_resize(addr, old_len, new_len, &charged);
 463         if (IS_ERR(vma)) {
 464                 ret = PTR_ERR(vma);
 465                 goto out;
 466         }
 467
 468         map_flags = MAP_FIXED;
 469         if (vma->vm_flags & VM_MAYSHARE)
 470                 map_flags |= MAP_SHARED;
 471
 472         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
 473                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
 474                                 map_flags);
 475         if (offset_in_page(ret))
 476                 goto out1;
 477
 478         ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf,
 479                        uf_unmap);
 480         if (!(offset_in_page(ret)))
 481                 goto out;
 482 out1:
 483         vm_unacct_memory(charged);
 484
 485 out:
 486         return ret;
 487 }
 488
 489 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 490 {
 491         unsigned long end = vma->vm_end + delta;
 492         if (end < vma->vm_end) /* overflow */
 493                 return 0;
 494         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
 495                 return 0;
 496         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
 497                               0, MAP_FIXED) & ~PAGE_MASK)
 498                 return 0;
 499         return 1;
 500 }
 501
 502 /*
 503  * Expand (or shrink) an existing mapping, potentially moving it at the
 504  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 505  *
 506  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 507  * This option implies MREMAP_MAYMOVE.
 508  */
 509 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 510                 unsigned long, new_len, unsigned long, flags,
 511                 unsigned long, new_addr)
 512 {
 513         struct mm_struct *mm = current->mm;
 514         struct vm_area_struct *vma;
 515         unsigned long ret = -EINVAL;
 516         unsigned long charged = 0;
 517         bool locked = false;
 518         struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
 519         LIST_HEAD(uf_unmap_early);
 520         LIST_HEAD(uf_unmap);
 521
 522         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 523                 return ret;
 524
 525         if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
 526                 return ret;
 527
 528         if (offset_in_page(addr))
 529                 return ret;
 530
 531         old_len = PAGE_ALIGN(old_len);
 532         new_len = PAGE_ALIGN(new_len);
 533
 534         /*
 535          * We allow a zero old-len as a special case
 536          * for DOS-emu "duplicate shm area" thing. But
 537          * a zero new-len is nonsensical.
 538          */
 539         if (!new_len)
 540                 return ret;
 541
 542         if (down_write_killable(&current->mm->mmap_sem))
 543                 return -EINTR;
 544
 545         if (flags & MREMAP_FIXED) {
 546                 ret = mremap_to(addr, old_len, new_addr, new_len,
 547                                 &locked, &uf, &uf_unmap_early, &uf_unmap);
 548                 goto out;
 549         }
 550
 551         /*
 552          * Always allow a shrinking remap: that just unmaps
 553          * the unnecessary pages..
 554          * do_munmap does all the needed commit accounting
 555          */
 556         if (old_len >= new_len) {
 557                 ret = do_munmap(mm, addr+new_len, old_len - new_len, &uf_unmap);
 558                 if (ret && old_len != new_len)
 559                         goto out;
 560                 ret = addr;
 561                 goto out;
 562         }
 563
 564         /*
 565          * Ok, we need to grow..
 566          */
 567         vma = vma_to_resize(addr, old_len, new_len, &charged);
 568         if (IS_ERR(vma)) {
 569                 ret = PTR_ERR(vma);
 570                 goto out;
 571         }
 572
 573         /* old_len exactly to the end of the area..
 574          */
 575         if (old_len == vma->vm_end - addr) {
 576                 /* can we just expand the current mapping? */
 577                 if (vma_expandable(vma, new_len - old_len)) {
 578                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 579
 580                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
 581                                        vma->vm_pgoff, NULL)) {
 582                                 ret = -ENOMEM;
 583                                 goto out;
 584                         }
 585
 586                         vm_stat_account(mm, vma->vm_flags, pages);
 587                         if (vma->vm_flags & VM_LOCKED) {
 588                                 mm->locked_vm += pages;
 589                                 locked = true;
 590                                 new_addr = addr;
 591                         }
 592                         ret = addr;
 593                         goto out;
 594                 }
 595         }
 596
 597         /*
 598          * We weren't able to just expand or shrink the area,
 599          * we need to create a new one and move it..
 600          */
 601         ret = -ENOMEM;
 602         if (flags & MREMAP_MAYMOVE) {
 603                 unsigned long map_flags = 0;
 604                 if (vma->vm_flags & VM_MAYSHARE)
 605                         map_flags |= MAP_SHARED;
 606
 607                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 608                                         vma->vm_pgoff +
 609                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
 610                                         map_flags);
 611                 if (offset_in_page(new_addr)) {
 612                         ret = new_addr;
 613                         goto out;
 614                 }
 615
 616                 ret = move_vma(vma, addr, old_len, new_len, new_addr,
 617                                &locked, &uf, &uf_unmap);
 618         }
 619 out:
 620         if (offset_in_page(ret)) {
 621                 vm_unacct_memory(charged);
 622                 locked = 0;
 623         }
 624         up_write(&current->mm->mmap_sem);
 625         if (locked && new_len > old_len)
 626                 mm_populate(new_addr + old_len, new_len - old_len);
 627         userfaultfd_unmap_complete(mm, &uf_unmap_early);
 628         mremap_userfaultfd_complete(&uf, addr, new_addr, old_len);
 629         userfaultfd_unmap_complete(mm, &uf_unmap);
 630         return ret;
 631 }