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 long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
  24 {
  25         struct file *file = fget(fd);
  26         struct inode *inode;
  27         struct address_space *mapping;
  28         struct backing_dev_info *bdi;
  29         int ret = 0;
  30
  31         if (!file)
  32                 return -EBADF;
  33
  34         inode = file->f_dentry->d_inode;
  35         mapping = inode->i_mapping;
  36         if (!mapping) {
  37                 ret = -EINVAL;
  38                 goto out;
  39         }
  40
  41         bdi = mapping->backing_dev_info;
  42
  43         switch (advice) {
  44         case POSIX_FADV_NORMAL:
  45                 file->f_ra.ra_pages = bdi->ra_pages;
  46                 break;
  47         case POSIX_FADV_RANDOM:
  48                 file->f_ra.ra_pages = 0;
  49                 break;
  50         case POSIX_FADV_SEQUENTIAL:
  51                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  52                 break;
  53         case POSIX_FADV_WILLNEED:
  54         case POSIX_FADV_NOREUSE:
  55                 if (!mapping->a_ops->readpage) {
  56                         ret = -EINVAL;
  57                         break;
  58                 }
  59                 ret = force_page_cache_readahead(mapping, file,
  60                                 offset >> PAGE_CACHE_SHIFT,
  61                                 max_sane_readahead(len >> PAGE_CACHE_SHIFT));
  62                 if (ret > 0)
  63                         ret = 0;
  64                 break;
  65         case POSIX_FADV_DONTNEED:
  66                 if (!bdi_write_congested(mapping->backing_dev_info))
  67                         filemap_flush(mapping);
  68                 invalidate_mapping_pages(mapping, offset >> PAGE_CACHE_SHIFT,
  69                                 (len >> PAGE_CACHE_SHIFT) + 1);
  70                 break;
  71         default:
  72                 ret = -EINVAL;
  73         }
  74 out:
  75         fput(file);
  76         return ret;
  77 }