linux/fs/romfs/mmap-nommu.c
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   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, maxpages, lpages;
  31        int ret;
  32
  33        if (!mtd)
  34                return (unsigned long) -ENOSYS;
  35
  36        /* the mapping mustn't extend beyond the EOF */
  37        lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
  38        isize = i_size_read(inode);
  39        offset = pgoff << PAGE_SHIFT;
  40
  41        maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
  42        if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
  43                return (unsigned long) -EINVAL;
  44
  45        if (addr != 0)
  46                return (unsigned long) -EINVAL;
  47
  48        if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
  49                return (unsigned long) -EINVAL;
  50
  51        offset += ROMFS_I(inode)->i_dataoffset;
  52        if (offset > mtd->size - len)
  53                return (unsigned long) -EINVAL;
  54
  55        ret = mtd_get_unmapped_area(mtd, len, offset, flags);
  56        if (ret == -EOPNOTSUPP)
  57                ret = -ENOSYS;
  58        return (unsigned long) ret;
  59}
  60
  61/*
  62 * permit a R/O mapping to be made directly through onto an MTD device if
  63 * possible
  64 */
  65static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
  66{
  67        return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
  68}
  69
  70const struct file_operations romfs_ro_fops = {
  71        .llseek                 = generic_file_llseek,
  72        .read                   = do_sync_read,
  73        .aio_read               = generic_file_aio_read,
  74        .splice_read            = generic_file_splice_read,
  75        .mmap                   = romfs_mmap,
  76        .get_unmapped_area      = romfs_get_unmapped_area,
  77};
  78
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