linux/mm/madvise.c
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   1/*
   2 *      linux/mm/madvise.c
   3 *
   4 * Copyright (C) 1999  Linus Torvalds
   5 * Copyright (C) 2002  Christoph Hellwig
   6 */
   7
   8#include <linux/mman.h>
   9#include <linux/pagemap.h>
  10#include <linux/syscalls.h>
  11#include <linux/mempolicy.h>
  12#include <linux/page-isolation.h>
  13#include <linux/hugetlb.h>
  14#include <linux/falloc.h>
  15#include <linux/sched.h>
  16#include <linux/ksm.h>
  17#include <linux/fs.h>
  18#include <linux/file.h>
  19
  20/*
  21 * Any behaviour which results in changes to the vma->vm_flags needs to
  22 * take mmap_sem for writing. Others, which simply traverse vmas, need
  23 * to only take it for reading.
  24 */
  25static int madvise_need_mmap_write(int behavior)
  26{
  27        switch (behavior) {
  28        case MADV_REMOVE:
  29        case MADV_WILLNEED:
  30        case MADV_DONTNEED:
  31                return 0;
  32        default:
  33                /* be safe, default to 1. list exceptions explicitly */
  34                return 1;
  35        }
  36}
  37
  38/*
  39 * We can potentially split a vm area into separate
  40 * areas, each area with its own behavior.
  41 */
  42static long madvise_behavior(struct vm_area_struct * vma,
  43                     struct vm_area_struct **prev,
  44                     unsigned long start, unsigned long end, int behavior)
  45{
  46        struct mm_struct * mm = vma->vm_mm;
  47        int error = 0;
  48        pgoff_t pgoff;
  49        unsigned long new_flags = vma->vm_flags;
  50
  51        switch (behavior) {
  52        case MADV_NORMAL:
  53                new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
  54                break;
  55        case MADV_SEQUENTIAL:
  56                new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
  57                break;
  58        case MADV_RANDOM:
  59                new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
  60                break;
  61        case MADV_DONTFORK:
  62                new_flags |= VM_DONTCOPY;
  63                break;
  64        case MADV_DOFORK:
  65                if (vma->vm_flags & VM_IO) {
  66                        error = -EINVAL;
  67                        goto out;
  68                }
  69                new_flags &= ~VM_DONTCOPY;
  70                break;
  71        case MADV_DONTDUMP:
  72                new_flags |= VM_DONTDUMP;
  73                break;
  74        case MADV_DODUMP:
  75                if (new_flags & VM_SPECIAL) {
  76                        error = -EINVAL;
  77                        goto out;
  78                }
  79                new_flags &= ~VM_DONTDUMP;
  80                break;
  81        case MADV_MERGEABLE:
  82        case MADV_UNMERGEABLE:
  83                error = ksm_madvise(vma, start, end, behavior, &new_flags);
  84                if (error)
  85                        goto out;
  86                break;
  87        case MADV_HUGEPAGE:
  88        case MADV_NOHUGEPAGE:
  89                error = hugepage_madvise(vma, &new_flags, behavior);
  90                if (error)
  91                        goto out;
  92                break;
  93        }
  94
  95        if (new_flags == vma->vm_flags) {
  96                *prev = vma;
  97                goto out;
  98        }
  99
 100        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 101        *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
 102                                vma->vm_file, pgoff, vma_policy(vma));
 103        if (*prev) {
 104                vma = *prev;
 105                goto success;
 106        }
 107
 108        *prev = vma;
 109
 110        if (start != vma->vm_start) {
 111                error = split_vma(mm, vma, start, 1);
 112                if (error)
 113                        goto out;
 114        }
 115
 116        if (end != vma->vm_end) {
 117                error = split_vma(mm, vma, end, 0);
 118                if (error)
 119                        goto out;
 120        }
 121
 122success:
 123        /*
 124         * vm_flags is protected by the mmap_sem held in write mode.
 125         */
 126        vma->vm_flags = new_flags;
 127
 128out:
 129        if (error == -ENOMEM)
 130                error = -EAGAIN;
 131        return error;
 132}
 133
 134/*
 135 * Schedule all required I/O operations.  Do not wait for completion.
 136 */
 137static long madvise_willneed(struct vm_area_struct * vma,
 138                             struct vm_area_struct ** prev,
 139                             unsigned long start, unsigned long end)
 140{
 141        struct file *file = vma->vm_file;
 142
 143        if (!file)
 144                return -EBADF;
 145
 146        if (file->f_mapping->a_ops->get_xip_mem) {
 147                /* no bad return value, but ignore advice */
 148                return 0;
 149        }
 150
 151        *prev = vma;
 152        start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 153        if (end > vma->vm_end)
 154                end = vma->vm_end;
 155        end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 156
 157        force_page_cache_readahead(file->f_mapping, file, start, end - start);
 158        return 0;
 159}
 160
 161/*
 162 * Application no longer needs these pages.  If the pages are dirty,
 163 * it's OK to just throw them away.  The app will be more careful about
 164 * data it wants to keep.  Be sure to free swap resources too.  The
 165 * zap_page_range call sets things up for shrink_active_list to actually free
 166 * these pages later if no one else has touched them in the meantime,
 167 * although we could add these pages to a global reuse list for
 168 * shrink_active_list to pick up before reclaiming other pages.
 169 *
 170 * NB: This interface discards data rather than pushes it out to swap,
 171 * as some implementations do.  This has performance implications for
 172 * applications like large transactional databases which want to discard
 173 * pages in anonymous maps after committing to backing store the data
 174 * that was kept in them.  There is no reason to write this data out to
 175 * the swap area if the application is discarding it.
 176 *
 177 * An interface that causes the system to free clean pages and flush
 178 * dirty pages is already available as msync(MS_INVALIDATE).
 179 */
 180static long madvise_dontneed(struct vm_area_struct * vma,
 181                             struct vm_area_struct ** prev,
 182                             unsigned long start, unsigned long end)
 183{
 184        *prev = vma;
 185        if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
 186                return -EINVAL;
 187
 188        if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
 189                struct zap_details details = {
 190                        .nonlinear_vma = vma,
 191                        .last_index = ULONG_MAX,
 192                };
 193                zap_page_range(vma, start, end - start, &details);
 194        } else
 195                zap_page_range(vma, start, end - start, NULL);
 196        return 0;
 197}
 198
 199/*
 200 * Application wants to free up the pages and associated backing store.
 201 * This is effectively punching a hole into the middle of a file.
 202 *
 203 * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
 204 * Other filesystems return -ENOSYS.
 205 */
 206static long madvise_remove(struct vm_area_struct *vma,
 207                                struct vm_area_struct **prev,
 208                                unsigned long start, unsigned long end)
 209{
 210        loff_t offset;
 211        int error;
 212        struct file *f;
 213
 214        *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
 215
 216        if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
 217                return -EINVAL;
 218
 219        f = vma->vm_file;
 220
 221        if (!f || !f->f_mapping || !f->f_mapping->host) {
 222                        return -EINVAL;
 223        }
 224
 225        if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 226                return -EACCES;
 227
 228        offset = (loff_t)(start - vma->vm_start)
 229                        + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 230
 231        /*
 232         * Filesystem's fallocate may need to take i_mutex.  We need to
 233         * explicitly grab a reference because the vma (and hence the
 234         * vma's reference to the file) can go away as soon as we drop
 235         * mmap_sem.
 236         */
 237        get_file(f);
 238        up_read(&current->mm->mmap_sem);
 239        error = do_fallocate(f,
 240                                FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 241                                offset, end - start);
 242        fput(f);
 243        down_read(&current->mm->mmap_sem);
 244        return error;
 245}
 246
 247#ifdef CONFIG_MEMORY_FAILURE
 248/*
 249 * Error injection support for memory error handling.
 250 */
 251static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
 252{
 253        int ret = 0;
 254
 255        if (!capable(CAP_SYS_ADMIN))
 256                return -EPERM;
 257        for (; start < end; start += PAGE_SIZE) {
 258                struct page *p;
 259                int ret = get_user_pages_fast(start, 1, 0, &p);
 260                if (ret != 1)
 261                        return ret;
 262                if (bhv == MADV_SOFT_OFFLINE) {
 263                        printk(KERN_INFO "Soft offlining page %lx at %lx\n",
 264                                page_to_pfn(p), start);
 265                        ret = soft_offline_page(p, MF_COUNT_INCREASED);
 266                        if (ret)
 267                                break;
 268                        continue;
 269                }
 270                printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n",
 271                       page_to_pfn(p), start);
 272                /* Ignore return value for now */
 273                memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED);
 274        }
 275        return ret;
 276}
 277#endif
 278
 279static long
 280madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 281                unsigned long start, unsigned long end, int behavior)
 282{
 283        switch (behavior) {
 284        case MADV_REMOVE:
 285                return madvise_remove(vma, prev, start, end);
 286        case MADV_WILLNEED:
 287                return madvise_willneed(vma, prev, start, end);
 288        case MADV_DONTNEED:
 289                return madvise_dontneed(vma, prev, start, end);
 290        default:
 291                return madvise_behavior(vma, prev, start, end, behavior);
 292        }
 293}
 294
 295static int
 296madvise_behavior_valid(int behavior)
 297{
 298        switch (behavior) {
 299        case MADV_DOFORK:
 300        case MADV_DONTFORK:
 301        case MADV_NORMAL:
 302        case MADV_SEQUENTIAL:
 303        case MADV_RANDOM:
 304        case MADV_REMOVE:
 305        case MADV_WILLNEED:
 306        case MADV_DONTNEED:
 307#ifdef CONFIG_KSM
 308        case MADV_MERGEABLE:
 309        case MADV_UNMERGEABLE:
 310#endif
 311#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 312        case MADV_HUGEPAGE:
 313        case MADV_NOHUGEPAGE:
 314#endif
 315        case MADV_DONTDUMP:
 316        case MADV_DODUMP:
 317                return 1;
 318
 319        default:
 320                return 0;
 321        }
 322}
 323
 324/*
 325 * The madvise(2) system call.
 326 *
 327 * Applications can use madvise() to advise the kernel how it should
 328 * handle paging I/O in this VM area.  The idea is to help the kernel
 329 * use appropriate read-ahead and caching techniques.  The information
 330 * provided is advisory only, and can be safely disregarded by the
 331 * kernel without affecting the correct operation of the application.
 332 *
 333 * behavior values:
 334 *  MADV_NORMAL - the default behavior is to read clusters.  This
 335 *              results in some read-ahead and read-behind.
 336 *  MADV_RANDOM - the system should read the minimum amount of data
 337 *              on any access, since it is unlikely that the appli-
 338 *              cation will need more than what it asks for.
 339 *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 340 *              once, so they can be aggressively read ahead, and
 341 *              can be freed soon after they are accessed.
 342 *  MADV_WILLNEED - the application is notifying the system to read
 343 *              some pages ahead.
 344 *  MADV_DONTNEED - the application is finished with the given range,
 345 *              so the kernel can free resources associated with it.
 346 *  MADV_REMOVE - the application wants to free up the given range of
 347 *              pages and associated backing store.
 348 *  MADV_DONTFORK - omit this area from child's address space when forking:
 349 *              typically, to avoid COWing pages pinned by get_user_pages().
 350 *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
 351 *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
 352 *              this area with pages of identical content from other such areas.
 353 *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
 354 *
 355 * return values:
 356 *  zero    - success
 357 *  -EINVAL - start + len < 0, start is not page-aligned,
 358 *              "behavior" is not a valid value, or application
 359 *              is attempting to release locked or shared pages.
 360 *  -ENOMEM - addresses in the specified range are not currently
 361 *              mapped, or are outside the AS of the process.
 362 *  -EIO    - an I/O error occurred while paging in data.
 363 *  -EBADF  - map exists, but area maps something that isn't a file.
 364 *  -EAGAIN - a kernel resource was temporarily unavailable.
 365 */
 366SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 367{
 368        unsigned long end, tmp;
 369        struct vm_area_struct * vma, *prev;
 370        int unmapped_error = 0;
 371        int error = -EINVAL;
 372        int write;
 373        size_t len;
 374
 375#ifdef CONFIG_MEMORY_FAILURE
 376        if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
 377                return madvise_hwpoison(behavior, start, start+len_in);
 378#endif
 379        if (!madvise_behavior_valid(behavior))
 380                return error;
 381
 382        write = madvise_need_mmap_write(behavior);
 383        if (write)
 384                down_write(&current->mm->mmap_sem);
 385        else
 386                down_read(&current->mm->mmap_sem);
 387
 388        if (start & ~PAGE_MASK)
 389                goto out;
 390        len = (len_in + ~PAGE_MASK) & PAGE_MASK;
 391
 392        /* Check to see whether len was rounded up from small -ve to zero */
 393        if (len_in && !len)
 394                goto out;
 395
 396        end = start + len;
 397        if (end < start)
 398                goto out;
 399
 400        error = 0;
 401        if (end == start)
 402                goto out;
 403
 404        /*
 405         * If the interval [start,end) covers some unmapped address
 406         * ranges, just ignore them, but return -ENOMEM at the end.
 407         * - different from the way of handling in mlock etc.
 408         */
 409        vma = find_vma_prev(current->mm, start, &prev);
 410        if (vma && start > vma->vm_start)
 411                prev = vma;
 412
 413        for (;;) {
 414                /* Still start < end. */
 415                error = -ENOMEM;
 416                if (!vma)
 417                        goto out;
 418
 419                /* Here start < (end|vma->vm_end). */
 420                if (start < vma->vm_start) {
 421                        unmapped_error = -ENOMEM;
 422                        start = vma->vm_start;
 423                        if (start >= end)
 424                                goto out;
 425                }
 426
 427                /* Here vma->vm_start <= start < (end|vma->vm_end) */
 428                tmp = vma->vm_end;
 429                if (end < tmp)
 430                        tmp = end;
 431
 432                /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
 433                error = madvise_vma(vma, &prev, start, tmp, behavior);
 434                if (error)
 435                        goto out;
 436                start = tmp;
 437                if (prev && start < prev->vm_end)
 438                        start = prev->vm_end;
 439                error = unmapped_error;
 440                if (start >= end)
 441                        goto out;
 442                if (prev)
 443                        vma = prev->vm_next;
 444                else    /* madvise_remove dropped mmap_sem */
 445                        vma = find_vma(current->mm, start);
 446        }
 447out:
 448        if (write)
 449                up_write(&current->mm->mmap_sem);
 450        else
 451                up_read(&current->mm->mmap_sem);
 452
 453        return error;
 454}
 455
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