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