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
 164         *prev = vma;
 165
 166         if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
 167                 return -EINVAL;
 168
 169         if (!vma->vm_file || !vma->vm_file->f_mapping
 170                 || !vma->vm_file->f_mapping->host) {
 171                         return -EINVAL;
 172         }
 173
 174         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 175                 return -EACCES;
 176
 177         mapping = vma->vm_file->f_mapping;
 178
 179         offset = (loff_t)(start - vma->vm_start)
 180                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 181         endoff = (loff_t)(end - vma->vm_start - 1)
 182                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 183         return  vmtruncate_range(mapping->host, offset, endoff);
 184 }
 185
 186 static long
 187 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 188                 unsigned long start, unsigned long end, int behavior)
 189 {
 190         long error;
 191
 192         switch (behavior) {
 193         case MADV_DOFORK:
 194                 if (vma->vm_flags & VM_IO) {
 195                         error = -EINVAL;
 196                         break;
 197                 }
 198         case MADV_DONTFORK:
 199         case MADV_NORMAL:
 200         case MADV_SEQUENTIAL:
 201         case MADV_RANDOM:
 202                 error = madvise_behavior(vma, prev, start, end, behavior);
 203                 break;
 204         case MADV_REMOVE:
 205                 error = madvise_remove(vma, prev, start, end);
 206                 break;
 207
 208         case MADV_WILLNEED:
 209                 error = madvise_willneed(vma, prev, start, end);
 210                 break;
 211
 212         case MADV_DONTNEED:
 213                 error = madvise_dontneed(vma, prev, start, end);
 214                 break;
 215
 216         default:
 217                 error = -EINVAL;
 218                 break;
 219         }
 220         return error;
 221 }
 222
 223 /*
 224  * The madvise(2) system call.
 225  *
 226  * Applications can use madvise() to advise the kernel how it should
 227  * handle paging I/O in this VM area.  The idea is to help the kernel
 228  * use appropriate read-ahead and caching techniques.  The information
 229  * provided is advisory only, and can be safely disregarded by the
 230  * kernel without affecting the correct operation of the application.
 231  *
 232  * behavior values:
 233  *  MADV_NORMAL - the default behavior is to read clusters.  This
 234  *              results in some read-ahead and read-behind.
 235  *  MADV_RANDOM - the system should read the minimum amount of data
 236  *              on any access, since it is unlikely that the appli-
 237  *              cation will need more than what it asks for.
 238  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 239  *              once, so they can be aggressively read ahead, and
 240  *              can be freed soon after they are accessed.
 241  *  MADV_WILLNEED - the application is notifying the system to read
 242  *              some pages ahead.
 243  *  MADV_DONTNEED - the application is finished with the given range,
 244  *              so the kernel can free resources associated with it.
 245  *  MADV_REMOVE - the application wants to free up the given range of
 246  *              pages and associated backing store.
 247  *
 248  * return values:
 249  *  zero    - success
 250  *  -EINVAL - start + len < 0, start is not page-aligned,
 251  *              "behavior" is not a valid value, or application
 252  *              is attempting to release locked or shared pages.
 253  *  -ENOMEM - addresses in the specified range are not currently
 254  *              mapped, or are outside the AS of the process.
 255  *  -EIO    - an I/O error occurred while paging in data.
 256  *  -EBADF  - map exists, but area maps something that isn't a file.
 257  *  -EAGAIN - a kernel resource was temporarily unavailable.
 258  */
 259 asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior)
 260 {
 261         unsigned long end, tmp;
 262         struct vm_area_struct * vma, *prev;
 263         int unmapped_error = 0;
 264         int error = -EINVAL;
 265         size_t len;
 266
 267         down_write(&current->mm->mmap_sem);
 268
 269         if (start & ~PAGE_MASK)
 270                 goto out;
 271         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
 272
 273         /* Check to see whether len was rounded up from small -ve to zero */
 274         if (len_in && !len)
 275                 goto out;
 276
 277         end = start + len;
 278         if (end < start)
 279                 goto out;
 280
 281         error = 0;
 282         if (end == start)
 283                 goto out;
 284
 285         /*
 286          * If the interval [start,end) covers some unmapped address
 287          * ranges, just ignore them, but return -ENOMEM at the end.
 288          * - different from the way of handling in mlock etc.
 289          */
 290         vma = find_vma_prev(current->mm, start, &prev);
 291         if (vma && start > vma->vm_start)
 292                 prev = vma;
 293
 294         for (;;) {
 295                 /* Still start < end. */
 296                 error = -ENOMEM;
 297                 if (!vma)
 298                         goto out;
 299
 300                 /* Here start < (end|vma->vm_end). */
 301                 if (start < vma->vm_start) {
 302                         unmapped_error = -ENOMEM;
 303                         start = vma->vm_start;
 304                         if (start >= end)
 305                                 goto out;
 306                 }
 307
 308                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
 309                 tmp = vma->vm_end;
 310                 if (end < tmp)
 311                         tmp = end;
 312
 313                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
 314                 error = madvise_vma(vma, &prev, start, tmp, behavior);
 315                 if (error)
 316                         goto out;
 317                 start = tmp;
 318                 if (start < prev->vm_end)
 319                         start = prev->vm_end;
 320                 error = unmapped_error;
 321                 if (start >= end)
 322                         goto out;
 323                 vma = prev->vm_next;
 324         }
 325 out:
 326         up_write(&current->mm->mmap_sem);
 327         return error;
 328 }