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/writeback.h>
  19 #include <linux/syscalls.h>
  20
  21 #include <asm/unistd.h>
  22
  23 /*
  24  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
  25  * deactivate the pages and clear PG_Referenced.
  26  */
  27 asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
  28 {
  29         struct file *file = fget(fd);
  30         struct address_space *mapping;
  31         struct backing_dev_info *bdi;
  32         loff_t endbyte;                 /* inclusive */
  33         pgoff_t start_index;
  34         pgoff_t end_index;
  35         unsigned long nrpages;
  36         int ret = 0;
  37
  38         if (!file)
  39                 return -EBADF;
  40
  41         if (S_ISFIFO(file->f_dentry->d_inode->i_mode)) {
  42                 ret = -ESPIPE;
  43                 goto out;
  44         }
  45
  46         mapping = file->f_mapping;
  47         if (!mapping || len < 0) {
  48                 ret = -EINVAL;
  49                 goto out;
  50         }
  51
  52         if (mapping->a_ops->get_xip_page)
  53                 /* no bad return value, but ignore advice */
  54                 goto out;
  55
  56         /* Careful about overflows. Len == 0 means "as much as possible" */
  57         endbyte = offset + len;
  58         if (!len || endbyte < len)
  59                 endbyte = -1;
  60         else
  61                 endbyte--;              /* inclusive */
  62
  63         bdi = mapping->backing_dev_info;
  64
  65         switch (advice) {
  66         case POSIX_FADV_NORMAL:
  67                 file->f_ra.ra_pages = bdi->ra_pages;
  68                 break;
  69         case POSIX_FADV_RANDOM:
  70                 file->f_ra.ra_pages = 0;
  71                 break;
  72         case POSIX_FADV_SEQUENTIAL:
  73                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  74                 break;
  75         case POSIX_FADV_WILLNEED:
  76         case POSIX_FADV_NOREUSE:
  77                 if (!mapping->a_ops->readpage) {
  78                         ret = -EINVAL;
  79                         break;
  80                 }
  81
  82                 /* First and last PARTIAL page! */
  83                 start_index = offset >> PAGE_CACHE_SHIFT;
  84                 end_index = endbyte >> PAGE_CACHE_SHIFT;
  85
  86                 /* Careful about overflow on the "+1" */
  87                 nrpages = end_index - start_index + 1;
  88                 if (!nrpages)
  89                         nrpages = ~0UL;
  90
  91                 ret = force_page_cache_readahead(mapping, file,
  92                                 start_index,
  93                                 max_sane_readahead(nrpages));
  94                 if (ret > 0)
  95                         ret = 0;
  96                 break;
  97         case POSIX_FADV_DONTNEED:
  98                 if (!bdi_write_congested(mapping->backing_dev_info))
  99                         filemap_flush(mapping);
 100
 101                 /* First and last FULL page! */
 102                 start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
 103                 end_index = (endbyte >> PAGE_CACHE_SHIFT);
 104
 105                 if (end_index >= start_index)
 106                         invalidate_mapping_pages(mapping, start_index,
 107                                                 end_index);
 108                 break;
 109         default:
 110                 ret = -EINVAL;
 111         }
 112 out:
 113         fput(file);
 114         return ret;
 115 }
 116
 117 #ifdef __ARCH_WANT_SYS_FADVISE64
 118
 119 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
 120 {
 121         return sys_fadvise64_64(fd, offset, len, advice);
 122 }
 123
 124 #endif