mmap-nommu.c
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/* NOMMU mmap support for RomFS on MTD devices
*
* Copyright © 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/mm.h>
#include <linux/mtd/super.h>
#include "internal.h"
/*
* try to determine where a shared mapping can be made
* - only supported for NOMMU at the moment (MMU can't doesn't copy private
* mappings)
* - attempts to map through to the underlying MTD device
*/
static unsigned long romfs_get_unmapped_area(struct file *file,
unsigned long addr,
unsigned long len,
unsigned long pgoff,
unsigned long flags)
{
struct inode *inode = file->f_mapping->host;
struct mtd_info *mtd = inode->i_sb->s_mtd;
unsigned long isize, offset, maxpages, lpages;
int ret;
if (!mtd)
return (unsigned long) -ENOSYS;
/* the mapping mustn't extend beyond the EOF */
lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
isize = i_size_read(inode);
offset = pgoff << PAGE_SHIFT;
maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
return (unsigned long) -EINVAL;
if (addr != 0)
return (unsigned long) -EINVAL;
if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
return (unsigned long) -EINVAL;
offset += ROMFS_I(inode)->i_dataoffset;
if (offset >= mtd->size)
return (unsigned long) -EINVAL;
/* the mapping mustn't extend beyond the EOF */
if ((offset + len) > mtd->size)
len = mtd->size - offset;
ret = mtd_get_unmapped_area(mtd, len, offset, flags);
if (ret == -EOPNOTSUPP)
ret = -ENOSYS;
return (unsigned long) ret;
}
/*
* permit a R/O mapping to be made directly through onto an MTD device if
* possible
*/
static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
{
return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
}
const struct file_operations romfs_ro_fops = {
.llseek = generic_file_llseek,
.read = do_sync_read,
.aio_read = generic_file_aio_read,
.splice_read = generic_file_splice_read,
.mmap = romfs_mmap,
.get_unmapped_area = romfs_get_unmapped_area,
};