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 #include <linux/syscalls.h>
  19
  20 #include <asm/unistd.h>
  21
  22 /*
  23  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
  24  * deactivate the pages and clear PG_Referenced.
  25  */
  26 asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
  27 {
  28         struct file *file = fget(fd);
  29         struct address_space *mapping;
  30         struct backing_dev_info *bdi;
  31         loff_t endbyte;
  32         pgoff_t start_index;
  33         pgoff_t end_index;
  34         unsigned long nrpages;
  35         int ret = 0;
  36
  37         if (!file)
  38                 return -EBADF;
  39
  40         mapping = file->f_mapping;
  41         if (!mapping || len < 0) {
  42                 ret = -EINVAL;
  43                 goto out;
  44         }
  45
  46         /* Careful about overflows. Len == 0 means "as much as possible" */
  47         endbyte = offset + len;
  48         if (!len || endbyte < len)
  49                 endbyte = -1;
  50
  51         bdi = mapping->backing_dev_info;
  52
  53         switch (advice) {
  54         case POSIX_FADV_NORMAL:
  55                 file->f_ra.ra_pages = bdi->ra_pages;
  56                 break;
  57         case POSIX_FADV_RANDOM:
  58                 file->f_ra.ra_pages = 0;
  59                 break;
  60         case POSIX_FADV_SEQUENTIAL:
  61                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  62                 break;
  63         case POSIX_FADV_WILLNEED:
  64         case POSIX_FADV_NOREUSE:
  65                 if (!mapping->a_ops->readpage) {
  66                         ret = -EINVAL;
  67                         break;
  68                 }
  69
  70                 /* First and last PARTIAL page! */
  71                 start_index = offset >> PAGE_CACHE_SHIFT;
  72                 end_index = (endbyte-1) >> PAGE_CACHE_SHIFT;
  73
  74                 /* Careful about overflow on the "+1" */
  75                 nrpages = end_index - start_index + 1;
  76                 if (!nrpages)
  77                         nrpages = ~0UL;
  78
  79                 ret = force_page_cache_readahead(mapping, file,
  80                                 start_index,
  81                                 max_sane_readahead(nrpages));
  82                 if (ret > 0)
  83                         ret = 0;
  84                 break;
  85         case POSIX_FADV_DONTNEED:
  86                 if (!bdi_write_congested(mapping->backing_dev_info))
  87                         filemap_flush(mapping);
  88
  89                 /* First and last FULL page! */
  90                 start_index = (offset + (PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
  91                 end_index = (endbyte >> PAGE_CACHE_SHIFT);
  92
  93                 if (end_index > start_index)
  94                         invalidate_mapping_pages(mapping, start_index, end_index-1);
  95                 break;
  96         default:
  97                 ret = -EINVAL;
  98         }
  99 out:
 100         fput(file);
 101         return ret;
 102 }
 103
 104 #ifdef __ARCH_WANT_SYS_FADVISE64
 105
 106 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
 107 {
 108         return sys_fadvise64_64(fd, offset, len, advice);
 109 }
 110
 111 #endif