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         if (mapping->a_ops->get_xip_page)
  47                 /* no bad return value, but ignore advice */
  48                 goto out;
  49
  50         /* Careful about overflows. Len == 0 means "as much as possible" */
  51         endbyte = offset + len;
  52         if (!len || endbyte < len)
  53                 endbyte = -1;
  54
  55         bdi = mapping->backing_dev_info;
  56
  57         switch (advice) {
  58         case POSIX_FADV_NORMAL:
  59                 file->f_ra.ra_pages = bdi->ra_pages;
  60                 break;
  61         case POSIX_FADV_RANDOM:
  62                 file->f_ra.ra_pages = 0;
  63                 break;
  64         case POSIX_FADV_SEQUENTIAL:
  65                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  66                 break;
  67         case POSIX_FADV_WILLNEED:
  68         case POSIX_FADV_NOREUSE:
  69                 if (!mapping->a_ops->readpage) {
  70                         ret = -EINVAL;
  71                         break;
  72                 }
  73
  74                 /* First and last PARTIAL page! */
  75                 start_index = offset >> PAGE_CACHE_SHIFT;
  76                 end_index = (endbyte-1) >> PAGE_CACHE_SHIFT;
  77
  78                 /* Careful about overflow on the "+1" */
  79                 nrpages = end_index - start_index + 1;
  80                 if (!nrpages)
  81                         nrpages = ~0UL;
  82
  83                 ret = force_page_cache_readahead(mapping, file,
  84                                 start_index,
  85                                 max_sane_readahead(nrpages));
  86                 if (ret > 0)
  87                         ret = 0;
  88                 break;
  89         case POSIX_FADV_DONTNEED:
  90                 if (!bdi_write_congested(mapping->backing_dev_info))
  91                         filemap_flush(mapping);
  92
  93                 /* First and last FULL page! */
  94                 start_index = (offset + (PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
  95                 end_index = (endbyte >> PAGE_CACHE_SHIFT);
  96
  97                 if (end_index > start_index)
  98                         invalidate_mapping_pages(mapping, start_index, end_index-1);
  99                 break;
 100         default:
 101                 ret = -EINVAL;
 102         }
 103 out:
 104         fput(file);
 105         return ret;
 106 }
 107
 108 #ifdef __ARCH_WANT_SYS_FADVISE64
 109
 110 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
 111 {
 112         return sys_fadvise64_64(fd, offset, len, advice);
 113 }
 114
 115 #endif