mm/madvise.c

   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/hugetlb.h>
  13
  14 /*
  15  * We can potentially split a vm area into separate
  16  * areas, each area with its own behavior.
  17  */
  18 static long madvise_behavior(struct vm_area_struct * vma,
  19                      struct vm_area_struct **prev,
  20                      unsigned long start, unsigned long end, int behavior)
  21 {
  22         struct mm_struct * mm = vma->vm_mm;
  23         int error = 0;
  24         pgoff_t pgoff;
  25         int new_flags = vma->vm_flags;
  26
  27         switch (behavior) {
  28         case MADV_NORMAL:
  29                 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
  30                 break;
  31         case MADV_SEQUENTIAL:
  32                 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
  33                 break;
  34         case MADV_RANDOM:
  35                 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
  36                 break;
  37         case MADV_DONTFORK:
  38                 new_flags |= VM_DONTCOPY;
  39                 break;
  40         case MADV_DOFORK:
  41                 new_flags &= ~VM_DONTCOPY;
  42                 break;
  43         }
  44
  45         if (new_flags == vma->vm_flags) {
  46                 *prev = vma;
  47                 goto out;
  48         }
  49
  50         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
  51         *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
  52                                 vma->vm_file, pgoff, vma_policy(vma));
  53         if (*prev) {
  54                 vma = *prev;
  55                 goto success;
  56         }
  57
  58         *prev = vma;
  59
  60         if (start != vma->vm_start) {
  61                 error = split_vma(mm, vma, start, 1);
  62                 if (error)
  63                         goto out;
  64         }
  65
  66         if (end != vma->vm_end) {
  67                 error = split_vma(mm, vma, end, 0);
  68                 if (error)
  69                         goto out;
  70         }
  71
  72 success:
  73         /*
  74          * vm_flags is protected by the mmap_sem held in write mode.
  75          */
  76         vma->vm_flags = new_flags;
  77
  78 out:
  79         if (error == -ENOMEM)
  80                 error = -EAGAIN;
  81         return error;
  82 }
  83
  84 /*
  85  * Schedule all required I/O operations.  Do not wait for completion.
  86  */
  87 static long madvise_willneed(struct vm_area_struct * vma,
  88                              struct vm_area_struct ** prev,
  89                              unsigned long start, unsigned long end)
  90 {
  91         struct file *file = vma->vm_file;
  92
  93         if (!file)
  94                 return -EBADF;
  95
  96         if (file->f_mapping->a_ops->get_xip_page) {
  97                 /* no bad return value, but ignore advice */
  98                 return 0;
  99         }
 100
 101         *prev = vma;
 102         start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 103         if (end > vma->vm_end)
 104                 end = vma->vm_end;
 105         end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 106
 107         force_page_cache_readahead(file->f_mapping,
 108                         file, start, max_sane_readahead(end - start));
 109         return 0;
 110 }
 111
 112 /*
 113  * Application no longer needs these pages.  If the pages are dirty,
 114  * it's OK to just throw them away.  The app will be more careful about
 115  * data it wants to keep.  Be sure to free swap resources too.  The
 116  * zap_page_range call sets things up for refill_inactive to actually free
 117  * these pages later if no one else has touched them in the meantime,
 118  * although we could add these pages to a global reuse list for
 119  * refill_inactive to pick up before reclaiming other pages.
 120  *
 121  * NB: This interface discards data rather than pushes it out to swap,
 122  * as some implementations do.  This has performance implications for
 123  * applications like large transactional databases which want to discard
 124  * pages in anonymous maps after committing to backing store the data
 125  * that was kept in them.  There is no reason to write this data out to
 126  * the swap area if the application is discarding it.
 127  *
 128  * An interface that causes the system to free clean pages and flush
 129  * dirty pages is already available as msync(MS_INVALIDATE).
 130  */
 131 static long madvise_dontneed(struct vm_area_struct * vma,
 132                              struct vm_area_struct ** prev,
 133                              unsigned long start, unsigned long end)
 134 {
 135         *prev = vma;
 136         if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
 137                 return -EINVAL;
 138
 139         if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
 140                 struct zap_details details = {
 141                         .nonlinear_vma = vma,
 142                         .last_index = ULONG_MAX,
 143                 };
 144                 zap_page_range(vma, start, end - start, &details);
 145         } else
 146                 zap_page_range(vma, start, end - start, NULL);
 147         return 0;
 148 }
 149
 150 /*
 151  * Application wants to free up the pages and associated backing store.
 152  * This is effectively punching a hole into the middle of a file.
 153  *
 154  * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
 155  * Other filesystems return -ENOSYS.
 156  */
 157 static long madvise_remove(struct vm_area_struct *vma,
 158                                 struct vm_area_struct **prev,
 159                                 unsigned long start, unsigned long end)
 160 {
 161         struct address_space *mapping;
 162         loff_t offset, endoff;
 163         int error;
 164
 165         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
 166
 167         if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
 168                 return -EINVAL;
 169
 170         if (!vma->vm_file || !vma->vm_file->f_mapping
 171                 || !vma->vm_file->f_mapping->host) {
 172                         return -EINVAL;
 173         }
 174
 175         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 176                 return -EACCES;
 177
 178         mapping = vma->vm_file->f_mapping;
 179
 180         offset = (loff_t)(start - vma->vm_start)
 181                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 182         endoff = (loff_t)(end - vma->vm_start - 1)
 183                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 184
 185         /* vmtruncate_range needs to take i_mutex and i_alloc_sem */
 186         up_write(&current->mm->mmap_sem);
 187         error = vmtruncate_range(mapping->host, offset, endoff);
 188         down_write(&current->mm->mmap_sem);
 189         return error;
 190 }
 191
 192 static long
 193 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 194                 unsigned long start, unsigned long end, int behavior)
 195 {
 196         long error;
 197
 198         switch (behavior) {
 199         case MADV_DOFORK:
 200                 if (vma->vm_flags & VM_IO) {
 201                         error = -EINVAL;
 202                         break;
 203                 }
 204         case MADV_DONTFORK:
 205         case MADV_NORMAL:
 206         case MADV_SEQUENTIAL:
 207         case MADV_RANDOM:
 208                 error = madvise_behavior(vma, prev, start, end, behavior);
 209                 break;
 210         case MADV_REMOVE:
 211                 error = madvise_remove(vma, prev, start, end);
 212                 break;
 213
 214         case MADV_WILLNEED:
 215                 error = madvise_willneed(vma, prev, start, end);
 216                 break;
 217
 218         case MADV_DONTNEED:
 219                 error = madvise_dontneed(vma, prev, start, end);
 220                 break;
 221
 222         default:
 223                 error = -EINVAL;
 224                 break;
 225         }
 226         return error;
 227 }
 228
 229 /*
 230  * The madvise(2) system call.
 231  *
 232  * Applications can use madvise() to advise the kernel how it should
 233  * handle paging I/O in this VM area.  The idea is to help the kernel
 234  * use appropriate read-ahead and caching techniques.  The information
 235  * provided is advisory only, and can be safely disregarded by the
 236  * kernel without affecting the correct operation of the application.
 237  *
 238  * behavior values:
 239  *  MADV_NORMAL - the default behavior is to read clusters.  This
 240  *              results in some read-ahead and read-behind.
 241  *  MADV_RANDOM - the system should read the minimum amount of data
 242  *              on any access, since it is unlikely that the appli-
 243  *              cation will need more than what it asks for.
 244  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 245  *              once, so they can be aggressively read ahead, and
 246  *              can be freed soon after they are accessed.
 247  *  MADV_WILLNEED - the application is notifying the system to read
 248  *              some pages ahead.
 249  *  MADV_DONTNEED - the application is finished with the given range,
 250  *              so the kernel can free resources associated with it.
 251  *  MADV_REMOVE - the application wants to free up the given range of
 252  *              pages and associated backing store.
 253  *
 254  * return values:
 255  *  zero    - success
 256  *  -EINVAL - start + len < 0, start is not page-aligned,
 257  *              "behavior" is not a valid value, or application
 258  *              is attempting to release locked or shared pages.
 259  *  -ENOMEM - addresses in the specified range are not currently
 260  *              mapped, or are outside the AS of the process.
 261  *  -EIO    - an I/O error occurred while paging in data.
 262  *  -EBADF  - map exists, but area maps something that isn't a file.
 263  *  -EAGAIN - a kernel resource was temporarily unavailable.
 264  */
 265 asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior)
 266 {
 267         unsigned long end, tmp;
 268         struct vm_area_struct * vma, *prev;
 269         int unmapped_error = 0;
 270         int error = -EINVAL;
 271         size_t len;
 272
 273         down_write(&current->mm->mmap_sem);
 274
 275         if (start & ~PAGE_MASK)
 276                 goto out;
 277         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
 278
 279         /* Check to see whether len was rounded up from small -ve to zero */
 280         if (len_in && !len)
 281                 goto out;
 282
 283         end = start + len;
 284         if (end < start)
 285                 goto out;
 286
 287         error = 0;
 288         if (end == start)
 289                 goto out;
 290
 291         /*
 292          * If the interval [start,end) covers some unmapped address
 293          * ranges, just ignore them, but return -ENOMEM at the end.
 294          * - different from the way of handling in mlock etc.
 295          */
 296         vma = find_vma_prev(current->mm, start, &prev);
 297         if (vma && start > vma->vm_start)
 298                 prev = vma;
 299
 300         for (;;) {
 301                 /* Still start < end. */
 302                 error = -ENOMEM;
 303                 if (!vma)
 304                         goto out;
 305
 306                 /* Here start < (end|vma->vm_end). */
 307                 if (start < vma->vm_start) {
 308                         unmapped_error = -ENOMEM;
 309                         start = vma->vm_start;
 310                         if (start >= end)
 311                                 goto out;
 312                 }
 313
 314                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
 315                 tmp = vma->vm_end;
 316                 if (end < tmp)
 317                         tmp = end;
 318
 319                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
 320                 error = madvise_vma(vma, &prev, start, tmp, behavior);
 321                 if (error)
 322                         goto out;
 323                 start = tmp;
 324                 if (prev && start < prev->vm_end)
 325                         start = prev->vm_end;
 326                 error = unmapped_error;
 327                 if (start >= end)
 328                         goto out;
 329                 if (prev)
 330                         vma = prev->vm_next;
 331                 else    /* madvise_remove dropped mmap_sem */
 332                         vma = find_vma(current->mm, start);
 333         }
 334 out:
 335         up_write(&current->mm->mmap_sem);
 336         return error;
 337 }