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  */
  22 static 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)
  53                 return (unsigned long) -EINVAL;
  54         /* the mapping mustn't extend beyond the EOF */
  55         if ((offset + len) > mtd->size)
  56                 len = mtd->size - offset;
  57
  58         ret = mtd_get_unmapped_area(mtd, len, offset, flags);
  59         if (ret == -EOPNOTSUPP)
  60                 ret = -ENOSYS;
  61         return (unsigned long) ret;
  62 }
  63
  64 /*
  65  * permit a R/O mapping to be made directly through onto an MTD device if
  66  * possible
  67  */
  68 static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
  69 {
  70         return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
  71 }
  72
  73 const struct file_operations romfs_ro_fops = {
  74         .llseek                 = generic_file_llseek,
  75         .read                   = new_sync_read,
  76         .read_iter              = generic_file_read_iter,
  77         .splice_read            = generic_file_splice_read,
  78         .mmap                   = romfs_mmap,
  79         .get_unmapped_area      = romfs_get_unmapped_area,
  80 };