LXR linux/fs/romfs/mmap-nommu.c

   1/* NOMMU mmap support for RomFS on MTD devices
   2 *
   3 * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the License, or (at your option) any later version.
  10 */
  11
  12#include <linux/mm.h>
  13#include <linux/mtd/super.h>
  14#include "internal.h"
  15
  16/*
  17 * try to determine where a shared mapping can be made
  18 * - only supported for NOMMU at the moment (MMU can't doesn't copy private
  19 *   mappings)
  20 * - attempts to map through to the underlying MTD device
  21 */
  22static unsigned long romfs_get_unmapped_area(struct file *file,
  23                                             unsigned long addr,
  24                                             unsigned long len,
  25                                             unsigned long pgoff,
  26                                             unsigned long flags)
  27{
  28        struct inode *inode = file->f_mapping->host;
  29        struct mtd_info *mtd = inode->i_sb->s_mtd;
  30        unsigned long isize, offset;
  31
  32        if (!mtd)
  33                goto cant_map_directly;
  34
  35        isize = i_size_read(inode);
  36        offset = pgoff << PAGE_SHIFT;
  37        if (offset > isize || len > isize || offset > isize - len)
  38                return (unsigned long) -EINVAL;
  39
  40        /* we need to call down to the MTD layer to do the actual mapping */
  41        if (mtd->get_unmapped_area) {
  42                if (addr != 0)
  43                        return (unsigned long) -EINVAL;
  44
  45                if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
  46                        return (unsigned long) -EINVAL;
  47
  48                offset += ROMFS_I(inode)->i_dataoffset;
  49                if (offset > mtd->size - len)
  50                        return (unsigned long) -EINVAL;
  51
  52                return mtd->get_unmapped_area(mtd, len, offset, flags);
  53        }
  54
  55cant_map_directly:
  56        return (unsigned long) -ENOSYS;
  57}
  58
  59/*
  60 * permit a R/O mapping to be made directly through onto an MTD device if
  61 * possible
  62 */
  63static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
  64{
  65        return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
  66}
  67
  68const struct file_operations romfs_ro_fops = {
  69        .llseek                 = generic_file_llseek,
  70        .read                   = do_sync_read,
  71        .aio_read               = generic_file_aio_read,
  72        .splice_read            = generic_file_splice_read,
  73        .mmap                   = romfs_mmap,
  74        .get_unmapped_area      = romfs_get_unmapped_area,
  75};
  76