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                                 unsigned long start, unsigned long end)
 159 {
 160         struct address_space *mapping;
 161         loff_t offset, endoff;
 162
 163         if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
 164                 return -EINVAL;
 165
 166         if (!vma->vm_file || !vma->vm_file->f_mapping
 167                 || !vma->vm_file->f_mapping->host) {
 168                         return -EINVAL;
 169         }
 170
 171         mapping = vma->vm_file->f_mapping;
 172
 173         offset = (loff_t)(start - vma->vm_start)
 174                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 175         endoff = (loff_t)(end - vma->vm_start - 1)
 176                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 177         return  vmtruncate_range(mapping->host, offset, endoff);
 178 }
 179
 180 static long
 181 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 182                 unsigned long start, unsigned long end, int behavior)
 183 {
 184         long error;
 185
 186         switch (behavior) {
 187         case MADV_DOFORK:
 188                 if (vma->vm_flags & VM_IO) {
 189                         error = -EINVAL;
 190                         break;
 191                 }
 192         case MADV_DONTFORK:
 193         case MADV_NORMAL:
 194         case MADV_SEQUENTIAL:
 195         case MADV_RANDOM:
 196                 error = madvise_behavior(vma, prev, start, end, behavior);
 197                 break;
 198         case MADV_REMOVE:
 199                 error = madvise_remove(vma, start, end);
 200                 break;
 201
 202         case MADV_WILLNEED:
 203                 error = madvise_willneed(vma, prev, start, end);
 204                 break;
 205
 206         case MADV_DONTNEED:
 207                 error = madvise_dontneed(vma, prev, start, end);
 208                 break;
 209
 210         default:
 211                 error = -EINVAL;
 212                 break;
 213         }
 214         return error;
 215 }
 216
 217 /*
 218  * The madvise(2) system call.
 219  *
 220  * Applications can use madvise() to advise the kernel how it should
 221  * handle paging I/O in this VM area.  The idea is to help the kernel
 222  * use appropriate read-ahead and caching techniques.  The information
 223  * provided is advisory only, and can be safely disregarded by the
 224  * kernel without affecting the correct operation of the application.
 225  *
 226  * behavior values:
 227  *  MADV_NORMAL - the default behavior is to read clusters.  This
 228  *              results in some read-ahead and read-behind.
 229  *  MADV_RANDOM - the system should read the minimum amount of data
 230  *              on any access, since it is unlikely that the appli-
 231  *              cation will need more than what it asks for.
 232  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 233  *              once, so they can be aggressively read ahead, and
 234  *              can be freed soon after they are accessed.
 235  *  MADV_WILLNEED - the application is notifying the system to read
 236  *              some pages ahead.
 237  *  MADV_DONTNEED - the application is finished with the given range,
 238  *              so the kernel can free resources associated with it.
 239  *  MADV_REMOVE - the application wants to free up the given range of
 240  *              pages and associated backing store.
 241  *
 242  * return values:
 243  *  zero    - success
 244  *  -EINVAL - start + len < 0, start is not page-aligned,
 245  *              "behavior" is not a valid value, or application
 246  *              is attempting to release locked or shared pages.
 247  *  -ENOMEM - addresses in the specified range are not currently
 248  *              mapped, or are outside the AS of the process.
 249  *  -EIO    - an I/O error occurred while paging in data.
 250  *  -EBADF  - map exists, but area maps something that isn't a file.
 251  *  -EAGAIN - a kernel resource was temporarily unavailable.
 252  */
 253 asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior)
 254 {
 255         unsigned long end, tmp;
 256         struct vm_area_struct * vma, *prev;
 257         int unmapped_error = 0;
 258         int error = -EINVAL;
 259         size_t len;
 260
 261         down_write(&current->mm->mmap_sem);
 262
 263         if (start & ~PAGE_MASK)
 264                 goto out;
 265         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
 266
 267         /* Check to see whether len was rounded up from small -ve to zero */
 268         if (len_in && !len)
 269                 goto out;
 270
 271         end = start + len;
 272         if (end < start)
 273                 goto out;
 274
 275         error = 0;
 276         if (end == start)
 277                 goto out;
 278
 279         /*
 280          * If the interval [start,end) covers some unmapped address
 281          * ranges, just ignore them, but return -ENOMEM at the end.
 282          * - different from the way of handling in mlock etc.
 283          */
 284         vma = find_vma_prev(current->mm, start, &prev);
 285         if (vma && start > vma->vm_start)
 286                 prev = vma;
 287
 288         for (;;) {
 289                 /* Still start < end. */
 290                 error = -ENOMEM;
 291                 if (!vma)
 292                         goto out;
 293
 294                 /* Here start < (end|vma->vm_end). */
 295                 if (start < vma->vm_start) {
 296                         unmapped_error = -ENOMEM;
 297                         start = vma->vm_start;
 298                         if (start >= end)
 299                                 goto out;
 300                 }
 301
 302                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
 303                 tmp = vma->vm_end;
 304                 if (end < tmp)
 305                         tmp = end;
 306
 307                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
 308                 error = madvise_vma(vma, &prev, start, tmp, behavior);
 309                 if (error)
 310                         goto out;
 311                 start = tmp;
 312                 if (start < prev->vm_end)
 313                         start = prev->vm_end;
 314                 error = unmapped_error;
 315                 if (start >= end)
 316                         goto out;
 317                 vma = prev->vm_next;
 318         }
 319 out:
 320         up_write(&current->mm->mmap_sem);
 321         return error;
 322 }