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