alistair23-linux/fs/romfs/mmap-nommu.c
Christoph Hellwig b4caecd480 fs: introduce f_op->mmap_capabilities for nommu mmap support
Since "BDI: Provide backing device capability information [try #3]" the
backing_dev_info structure also provides flags for the kind of mmap
operation available in a nommu environment, which is entirely unrelated
to it's original purpose.

Introduce a new nommu-only file operation to provide this information to
the nommu mmap code instead.  Splitting this from the backing_dev_info
structure allows to remove lots of backing_dev_info instance that aren't
otherwise needed, and entirely gets rid of the concept of providing a
backing_dev_info for a character device.  It also removes the need for
the mtd_inodefs filesystem.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2015-01-20 14:02:58 -07:00

91 lines
2.5 KiB
C

/* 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;
}
static unsigned romfs_mmap_capabilities(struct file *file)
{
struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
if (!mtd)
return NOMMU_MAP_COPY;
return mtd_mmap_capabilities(mtd);
}
const struct file_operations romfs_ro_fops = {
.llseek = generic_file_llseek,
.read = new_sync_read,
.read_iter = generic_file_read_iter,
.splice_read = generic_file_splice_read,
.mmap = romfs_mmap,
.get_unmapped_area = romfs_get_unmapped_area,
.mmap_capabilities = romfs_mmap_capabilities,
};