linux/fs/no-block.c

/* no-block.c: implementation of routines required for non-BLOCK configuration
 *
 * Copyright (C) 2006 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/kernel.h>
#include <linux/fs.h>

static int no_blkdev_open(struct inode * inode, struct file * filp)
{
	return -ENODEV;
}

const struct file_operations def_blk_fops = {
	.open		= no_blkdev_open,
};
[PATCH] BLOCK: Make it possible to disable the block layer [try #6] Make it possible to disable the block layer. Not all embedded devices require it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require the block layer to be present. This patch does the following: () Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev support. () Adds dependencies on CONFIG_BLOCK to any configuration item that controls an item that uses the block layer. This includes: () Block I/O tracing. () Disk partition code. () All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS. () The SCSI layer. As far as I can tell, even SCSI chardevs use the block layer to do scheduling. Some drivers that use SCSI facilities - such as USB storage - end up disabled indirectly from this. () Various block-based device drivers, such as IDE and the old CDROM drivers. () MTD blockdev handling and FTL. () JFFS - which uses set_bdev_super(), something it could avoid doing by taking a leaf out of JFFS2's book. () Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is, however, still used in places, and so is still available. () Also made contingent are the contents of linux/mpage.h, linux/genhd.h and parts of linux/fs.h. () Makes a number of files in fs/ contingent on CONFIG_BLOCK. () Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK. () set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK is not enabled. () fs/no-block.c is created to hold out-of-line stubs and things that are required when CONFIG_BLOCK is not set: () Default blockdev file operations (to give error ENODEV on opening). () Makes some /proc changes: () /proc/devices does not list any blockdevs. () /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK. () Makes some compat ioctl handling contingent on CONFIG_BLOCK. () If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if given command other than Q_SYNC or if a special device is specified. () In init/do_mounts.c, no reference is made to the blockdev routines if CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2. () The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return error ENOSYS by way of cond_syscall if so). () The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if CONFIG_BLOCK is not set, since they can't then happen. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> 2006-09-30 18:45:40 +00:00			`/* no-block.c: implementation of routines required for non-BLOCK configuration`
			`*`
			`* Copyright (C) 2006 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/kernel.h>`
			`#include <linux/fs.h>`

			`static int no_blkdev_open(struct inode * inode, struct file * filp)`
			`{`
			`return -ENODEV;`
			`}`

			`const struct file_operations def_blk_fops = {`
			`.open = no_blkdev_open,`
			`};`