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Revision a84a79e4d369a73c0130b5858199e949432da4c6 authored by Linus Torvalds on 17 October 2011, 15:24:24 UTC, committed by Linus Torvalds on 17 October 2011, 15:24:24 UTC 
Avoid using variable-length arrays in kernel/sys.c
 
The size is always valid, but variable-length arrays generate worse code
for no good reason (unless the function happens to be inlined and the
compiler sees the length for the simple constant it is).

Also, there seems to be some code generation problem on POWER, where
Henrik Bakken reports that register r28 can get corrupted under some
subtle circumstances (interrupt happening at the wrong time?).  That all
indicates some seriously broken compiler issues, but since variable
length arrays are bad regardless, there's little point in trying to
chase it down.

"Just don't do that, then".

Reported-by: Henrik Grindal Bakken <henribak@cisco.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 8bc03e8
Raw File
dm-target.c 
/*
 * Copyright (C) 2001 Sistina Software (UK) Limited
 *
 * This file is released under the GPL.
 */

#include "dm.h"

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <linux/bio.h>

#define DM_MSG_PREFIX "target"

static LIST_HEAD(_targets);
static DECLARE_RWSEM(_lock);

#define DM_MOD_NAME_SIZE 32

static inline struct target_type *__find_target_type(const char *name)
{
	struct target_type *tt;

	list_for_each_entry(tt, &_targets, list)
		if (!strcmp(name, tt->name))
			return tt;

	return NULL;
}

static struct target_type *get_target_type(const char *name)
{
	struct target_type *tt;

	down_read(&_lock);

	tt = __find_target_type(name);
	if (tt && !try_module_get(tt->module))
		tt = NULL;

	up_read(&_lock);
	return tt;
}

static void load_module(const char *name)
{
	request_module("dm-%s", name);
}

struct target_type *dm_get_target_type(const char *name)
{
	struct target_type *tt = get_target_type(name);

	if (!tt) {
		load_module(name);
		tt = get_target_type(name);
	}

	return tt;
}

void dm_put_target_type(struct target_type *tt)
{
	down_read(&_lock);
	module_put(tt->module);
	up_read(&_lock);
}

int dm_target_iterate(void (*iter_func)(struct target_type *tt,
					void *param), void *param)
{
	struct target_type *tt;

	down_read(&_lock);
	list_for_each_entry(tt, &_targets, list)
		iter_func(tt, param);
	up_read(&_lock);

	return 0;
}

int dm_register_target(struct target_type *tt)
{
	int rv = 0;

	down_write(&_lock);
	if (__find_target_type(tt->name))
		rv = -EEXIST;
	else
		list_add(&tt->list, &_targets);

	up_write(&_lock);
	return rv;
}

void dm_unregister_target(struct target_type *tt)
{
	down_write(&_lock);
	if (!__find_target_type(tt->name)) {
		DMCRIT("Unregistering unrecognised target: %s", tt->name);
		BUG();
	}

	list_del(&tt->list);

	up_write(&_lock);
}

/*
 * io-err: always fails an io, useful for bringing
 * up LVs that have holes in them.
 */
static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
{
	/*
	 * Return error for discards instead of -EOPNOTSUPP
	 */
	tt->num_discard_requests = 1;

	return 0;
}

static void io_err_dtr(struct dm_target *tt)
{
	/* empty */
}

static int io_err_map(struct dm_target *tt, struct bio *bio,
		      union map_info *map_context)
{
	return -EIO;
}

static struct target_type error_target = {
	.name = "error",
	.version = {1, 0, 1},
	.ctr  = io_err_ctr,
	.dtr  = io_err_dtr,
	.map  = io_err_map,
};

int __init dm_target_init(void)
{
	return dm_register_target(&error_target);
}

void dm_target_exit(void)
{
	dm_unregister_target(&error_target);
}

EXPORT_SYMBOL(dm_register_target);
EXPORT_SYMBOL(dm_unregister_target);
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