LXR linux/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 */
  27asmlinkage 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_path.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                if (!mapping->a_ops->readpage) {
  77                        ret = -EINVAL;
  78                        break;
  79                }
  80
  81                /* First and last PARTIAL page! */
  82                start_index = offset >> PAGE_CACHE_SHIFT;
  83                end_index = endbyte >> PAGE_CACHE_SHIFT;
  84
  85                /* Careful about overflow on the "+1" */
  86                nrpages = end_index - start_index + 1;
  87                if (!nrpages)
  88                        nrpages = ~0UL;
  89                
  90                ret = force_page_cache_readahead(mapping, file,
  91                                start_index,
  92                                max_sane_readahead(nrpages));
  93                if (ret > 0)
  94                        ret = 0;
  95                break;
  96        case POSIX_FADV_NOREUSE:
  97                break;
  98        case POSIX_FADV_DONTNEED:
  99                if (!bdi_write_congested(mapping->backing_dev_info))
 100                        filemap_flush(mapping);
 101
 102                /* First and last FULL page! */
 103                start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
 104                end_index = (endbyte >> PAGE_CACHE_SHIFT);
 105
 106                if (end_index >= start_index)
 107                        invalidate_mapping_pages(mapping, start_index,
 108                                                end_index);
 109                break;
 110        default:
 111                ret = -EINVAL;
 112        }
 113out:
 114        fput(file);
 115        return ret;
 116}
 117
 118#ifdef __ARCH_WANT_SYS_FADVISE64
 119
 120asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
 121{
 122        return sys_fadvise64_64(fd, offset, len, advice);
 123}
 124
 125#endif
 126