mm/fadvise.c

   1 /*
   2  * mm/fadvise.c
   3  *
   4  * Copyright (C) 2002, Linus Torvalds
   5  *
   6  * 11Jan2003    akpm@digeo.com
   7  *              Initial version.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/file.h>
  12 #include <linux/fs.h>
  13 #include <linux/mm.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/backing-dev.h>
  16 #include <linux/pagevec.h>
  17 #include <linux/fadvise.h>
  18
  19 /*
  20  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
  21  * deactivate the pages and clear PG_Referenced.
  22  */
  23 asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
  24 {
  25         struct file *file = fget(fd);
  26         struct address_space *mapping;
  27         struct backing_dev_info *bdi;
  28         loff_t endbyte;
  29         pgoff_t start_index;
  30         pgoff_t end_index;
  31         unsigned long nrpages;
  32         int ret = 0;
  33
  34         if (!file)
  35                 return -EBADF;
  36
  37         mapping = file->f_mapping;
  38         if (!mapping || len < 0) {
  39                 ret = -EINVAL;
  40                 goto out;
  41         }
  42
  43         /* Careful about overflows. Len == 0 means "as much as possible" */
  44         endbyte = offset + len;
  45         if (!len || endbyte < len)
  46                 endbyte = -1;
  47
  48         bdi = mapping->backing_dev_info;
  49
  50         switch (advice) {
  51         case POSIX_FADV_NORMAL:
  52                 file->f_ra.ra_pages = bdi->ra_pages;
  53                 break;
  54         case POSIX_FADV_RANDOM:
  55                 file->f_ra.ra_pages = 0;
  56                 break;
  57         case POSIX_FADV_SEQUENTIAL:
  58                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  59                 break;
  60         case POSIX_FADV_WILLNEED:
  61         case POSIX_FADV_NOREUSE:
  62                 if (!mapping->a_ops->readpage) {
  63                         ret = -EINVAL;
  64                         break;
  65                 }
  66
  67                 /* First and last PARTIAL page! */
  68                 start_index = offset >> PAGE_CACHE_SHIFT;
  69                 end_index = (endbyte-1) >> PAGE_CACHE_SHIFT;
  70
  71                 /* Careful about overflow on the "+1" */
  72                 nrpages = end_index - start_index + 1;
  73                 if (!nrpages)
  74                         nrpages = ~0UL;
  75
  76                 ret = force_page_cache_readahead(mapping, file,
  77                                 start_index,
  78                                 max_sane_readahead(nrpages));
  79                 if (ret > 0)
  80                         ret = 0;
  81                 break;
  82         case POSIX_FADV_DONTNEED:
  83                 if (!bdi_write_congested(mapping->backing_dev_info))
  84                         filemap_flush(mapping);
  85
  86                 /* First and last FULL page! */
  87                 start_index = (offset + (PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
  88                 end_index = (endbyte >> PAGE_CACHE_SHIFT);
  89
  90                 if (end_index > start_index)
  91                         invalidate_mapping_pages(mapping, start_index, end_index-1);
  92                 break;
  93         default:
  94                 ret = -EINVAL;
  95         }
  96 out:
  97         fput(file);
  98         return ret;
  99 }
 100
 101 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
 102 {
 103         return sys_fadvise64_64(fd, offset, len, advice);
 104 }
 105