LXR linux/mm/fadvise.c

   1/*
   2 * mm/fadvise.c
   3 *
   4 * Copyright (C) 2002, Linus Torvalds
   5 *
   6 * 11Jan2003    Andrew Morton
   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 */
  27SYSCALL_DEFINE(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_mem) {
  53                switch (advice) {
  54                case POSIX_FADV_NORMAL:
  55                case POSIX_FADV_RANDOM:
  56                case POSIX_FADV_SEQUENTIAL:
  57                case POSIX_FADV_WILLNEED:
  58                case POSIX_FADV_NOREUSE:
  59                case POSIX_FADV_DONTNEED:
  60                        /* no bad return value, but ignore advice */
  61                        break;
  62                default:
  63                        ret = -EINVAL;
  64                }
  65                goto out;
  66        }
  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                if (!mapping->a_ops->readpage) {
  89                        ret = -EINVAL;
  90                        break;
  91                }
  92
  93                /* First and last PARTIAL page! */
  94                start_index = offset >> PAGE_CACHE_SHIFT;
  95                end_index = endbyte >> PAGE_CACHE_SHIFT;
  96
  97                /* Careful about overflow on the "+1" */
  98                nrpages = end_index - start_index + 1;
  99                if (!nrpages)
 100                        nrpages = ~0UL;
 101                
 102                ret = force_page_cache_readahead(mapping, file,
 103                                start_index,
 104                                nrpages);
 105                if (ret > 0)
 106                        ret = 0;
 107                break;
 108        case POSIX_FADV_NOREUSE:
 109                break;
 110        case POSIX_FADV_DONTNEED:
 111                if (!bdi_write_congested(mapping->backing_dev_info))
 112                        filemap_flush(mapping);
 113
 114                /* First and last FULL page! */
 115                start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
 116                end_index = (endbyte >> PAGE_CACHE_SHIFT);
 117
 118                if (end_index >= start_index)
 119                        invalidate_mapping_pages(mapping, start_index,
 120                                                end_index);
 121                break;
 122        default:
 123                ret = -EINVAL;
 124        }
 125out:
 126        fput(file);
 127        return ret;
 128}
 129#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 130asmlinkage long SyS_fadvise64_64(long fd, loff_t offset, loff_t len, long advice)
 131{
 132        return SYSC_fadvise64_64((int) fd, offset, len, (int) advice);
 133}
 134SYSCALL_ALIAS(sys_fadvise64_64, SyS_fadvise64_64);
 135#endif
 136
 137#ifdef __ARCH_WANT_SYS_FADVISE64
 138
 139SYSCALL_DEFINE(fadvise64)(int fd, loff_t offset, size_t len, int advice)
 140{
 141        return sys_fadvise64_64(fd, offset, len, advice);
 142}
 143#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 144asmlinkage long SyS_fadvise64(long fd, loff_t offset, long len, long advice)
 145{
 146        return SYSC_fadvise64((int) fd, offset, (size_t)len, (int)advice);
 147}
 148SYSCALL_ALIAS(sys_fadvise64, SyS_fadvise64);
 149#endif
 150
 151#endif
 152