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  * LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file
  28  * offsets `offset' and `offset+len' inclusive.  Any pages which are currently
  29  * under writeout are skipped, whether or not they are dirty.
  30  *
  31  * LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file
  32  * offsets `offset' and `offset+len'.
  33  *
  34  * By combining these two operations the application may do several things:
  35  *
  36  * LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk.
  37  *
  38  */
  39 asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
  40 {
  41         struct file *file = fget(fd);
  42         struct address_space *mapping;
  43         struct backing_dev_info *bdi;
  44         loff_t endbyte;                 /* inclusive */
  45         pgoff_t start_index;
  46         pgoff_t end_index;
  47         unsigned long nrpages;
  48         int ret = 0;
  49
  50         if (!file)
  51                 return -EBADF;
  52
  53         if (S_ISFIFO(file->f_dentry->d_inode->i_mode)) {
  54                 ret = -ESPIPE;
  55                 goto out;
  56         }
  57
  58         mapping = file->f_mapping;
  59         if (!mapping || len < 0) {
  60                 ret = -EINVAL;
  61                 goto out;
  62         }
  63
  64         if (mapping->a_ops->get_xip_page)
  65                 /* no bad return value, but ignore advice */
  66                 goto out;
  67
  68         /* Careful about overflows. Len == 0 means "as much as possible" */
  69         endbyte = offset + len;
  70         if (!len || endbyte < len)
  71                 endbyte = -1;
  72         else
  73                 endbyte--;              /* inclusive */
  74
  75         bdi = mapping->backing_dev_info;
  76
  77         switch (advice) {
  78         case POSIX_FADV_NORMAL:
  79                 file->f_ra.ra_pages = bdi->ra_pages;
  80                 break;
  81         case POSIX_FADV_RANDOM:
  82                 file->f_ra.ra_pages = 0;
  83                 break;
  84         case POSIX_FADV_SEQUENTIAL:
  85                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  86                 break;
  87         case POSIX_FADV_WILLNEED:
  88         case POSIX_FADV_NOREUSE:
  89                 if (!mapping->a_ops->readpage) {
  90                         ret = -EINVAL;
  91                         break;
  92                 }
  93
  94                 /* First and last PARTIAL page! */
  95                 start_index = offset >> PAGE_CACHE_SHIFT;
  96                 end_index = endbyte >> PAGE_CACHE_SHIFT;
  97
  98                 /* Careful about overflow on the "+1" */
  99                 nrpages = end_index - start_index + 1;
 100                 if (!nrpages)
 101                         nrpages = ~0UL;
 102
 103                 ret = force_page_cache_readahead(mapping, file,
 104                                 start_index,
 105                                 max_sane_readahead(nrpages));
 106                 if (ret > 0)
 107                         ret = 0;
 108                 break;
 109         case POSIX_FADV_DONTNEED:
 110                 if (!bdi_write_congested(mapping->backing_dev_info))
 111                         filemap_flush(mapping);
 112
 113                 /* First and last FULL page! */
 114                 start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
 115                 end_index = (endbyte >> PAGE_CACHE_SHIFT);
 116
 117                 if (end_index >= start_index)
 118                         invalidate_mapping_pages(mapping, start_index,
 119                                                 end_index);
 120                 break;
 121         default:
 122                 ret = -EINVAL;
 123         }
 124 out:
 125         fput(file);
 126         return ret;
 127 }
 128
 129 #ifdef __ARCH_WANT_SYS_FADVISE64
 130
 131 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
 132 {
 133         return sys_fadvise64_64(fd, offset, len, advice);
 134 }
 135
 136 #endif