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         if (S_ISFIFO(file->f_dentry->d_inode->i_mode)) {
  41                 ret = -ESPIPE;
  42                 goto out;
  43         }
  44
  45         mapping = file->f_mapping;
  46         if (!mapping || len < 0) {
  47                 ret = -EINVAL;
  48                 goto out;
  49         }
  50
  51         if (mapping->a_ops->get_xip_page)
  52                 /* no bad return value, but ignore advice */
  53                 goto out;
  54
  55         /* Careful about overflows. Len == 0 means "as much as possible" */
  56         endbyte = offset + len;
  57         if (!len || endbyte < len)
  58                 endbyte = -1;
  59
  60         bdi = mapping->backing_dev_info;
  61
  62         switch (advice) {
  63         case POSIX_FADV_NORMAL:
  64                 file->f_ra.ra_pages = bdi->ra_pages;
  65                 break;
  66         case POSIX_FADV_RANDOM:
  67                 file->f_ra.ra_pages = 0;
  68                 break;
  69         case POSIX_FADV_SEQUENTIAL:
  70                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  71                 break;
  72         case POSIX_FADV_WILLNEED:
  73         case POSIX_FADV_NOREUSE:
  74                 if (!mapping->a_ops->readpage) {
  75                         ret = -EINVAL;
  76                         break;
  77                 }
  78
  79                 /* First and last PARTIAL page! */
  80                 start_index = offset >> PAGE_CACHE_SHIFT;
  81                 end_index = (endbyte-1) >> PAGE_CACHE_SHIFT;
  82
  83                 /* Careful about overflow on the "+1" */
  84                 nrpages = end_index - start_index + 1;
  85                 if (!nrpages)
  86                         nrpages = ~0UL;
  87
  88                 ret = force_page_cache_readahead(mapping, file,
  89                                 start_index,
  90                                 max_sane_readahead(nrpages));
  91                 if (ret > 0)
  92                         ret = 0;
  93                 break;
  94         case POSIX_FADV_DONTNEED:
  95                 if (!bdi_write_congested(mapping->backing_dev_info))
  96                         filemap_flush(mapping);
  97
  98                 /* First and last FULL page! */
  99                 start_index = (offset + (PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
 100                 end_index = (endbyte >> PAGE_CACHE_SHIFT);
 101
 102                 if (end_index > start_index)
 103                         invalidate_mapping_pages(mapping, start_index, end_index-1);
 104                 break;
 105         default:
 106                 ret = -EINVAL;
 107         }
 108 out:
 109         fput(file);
 110         return ret;
 111 }
 112
 113 #ifdef __ARCH_WANT_SYS_FADVISE64
 114
 115 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
 116 {
 117         return sys_fadvise64_64(fd, offset, len, advice);
 118 }
 119
 120 #endif