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linux-next/drivers/md/dm-path-selector.c
Jun'ichi Nomura aea9058801 dm: path selector use module refcount directly
Fix refcount corruption in dm-path-selector

Refcounting with non-atomic ops under shared lock will corrupt the counter
in multi-processor system and may trigger BUG_ON().
Use module refcount.
# same approach as dm-target-use-module-refcount-directly.patch here
# https://www.redhat.com/archives/dm-devel/2008-December/msg00075.html

Typical oops:
  kernel BUG at linux-2.6.29-rc3/drivers/md/dm-path-selector.c:90!
  Pid: 11148, comm: dmsetup Not tainted 2.6.29-rc3-nm 
  dm_put_path_selector+0x4d/0x61 [dm_multipath]
  Call Trace:
   [<ffffffffa031d3f9>] free_priority_group+0x33/0xb3 [dm_multipath]
   [<ffffffffa031d4aa>] free_multipath+0x31/0x67 [dm_multipath]
   [<ffffffffa031d50d>] multipath_dtr+0x2d/0x32 [dm_multipath]
   [<ffffffffa015d6c2>] dm_table_destroy+0x64/0xd8 [dm_mod]
   [<ffffffffa015b73a>] __unbind+0x46/0x4b [dm_mod]
   [<ffffffffa015b79f>] dm_swap_table+0x60/0x14d [dm_mod]
   [<ffffffffa015f963>] dev_suspend+0xfd/0x177 [dm_mod]
   [<ffffffffa0160250>] dm_ctl_ioctl+0x24c/0x29c [dm_mod]
   [<ffffffff80288cd3>] ? get_page_from_freelist+0x49c/0x61d
   [<ffffffffa015f866>] ? dev_suspend+0x0/0x177 [dm_mod]
   [<ffffffff802bf05c>] vfs_ioctl+0x2a/0x77
   [<ffffffff802bf4f1>] do_vfs_ioctl+0x448/0x4a0
   [<ffffffff802bf5a0>] sys_ioctl+0x57/0x7a
   [<ffffffff8020c05b>] system_call_fastpath+0x16/0x1b

Cc: stable@kernel.org
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:27 +01:00

140 lines
2.4 KiB
C

/*
* Copyright (C) 2003 Sistina Software.
* Copyright (C) 2004 Red Hat, Inc. All rights reserved.
*
* Module Author: Heinz Mauelshagen
*
* This file is released under the GPL.
*
* Path selector registration.
*/
#include <linux/device-mapper.h>
#include "dm-path-selector.h"
#include <linux/slab.h>
struct ps_internal {
struct path_selector_type pst;
struct list_head list;
};
#define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
static LIST_HEAD(_path_selectors);
static DECLARE_RWSEM(_ps_lock);
static struct ps_internal *__find_path_selector_type(const char *name)
{
struct ps_internal *psi;
list_for_each_entry(psi, &_path_selectors, list) {
if (!strcmp(name, psi->pst.name))
return psi;
}
return NULL;
}
static struct ps_internal *get_path_selector(const char *name)
{
struct ps_internal *psi;
down_read(&_ps_lock);
psi = __find_path_selector_type(name);
if (psi && !try_module_get(psi->pst.module))
psi = NULL;
up_read(&_ps_lock);
return psi;
}
struct path_selector_type *dm_get_path_selector(const char *name)
{
struct ps_internal *psi;
if (!name)
return NULL;
psi = get_path_selector(name);
if (!psi) {
request_module("dm-%s", name);
psi = get_path_selector(name);
}
return psi ? &psi->pst : NULL;
}
void dm_put_path_selector(struct path_selector_type *pst)
{
struct ps_internal *psi;
if (!pst)
return;
down_read(&_ps_lock);
psi = __find_path_selector_type(pst->name);
if (!psi)
goto out;
module_put(psi->pst.module);
out:
up_read(&_ps_lock);
}
static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
{
struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);
if (psi)
psi->pst = *pst;
return psi;
}
int dm_register_path_selector(struct path_selector_type *pst)
{
int r = 0;
struct ps_internal *psi = _alloc_path_selector(pst);
if (!psi)
return -ENOMEM;
down_write(&_ps_lock);
if (__find_path_selector_type(pst->name)) {
kfree(psi);
r = -EEXIST;
} else
list_add(&psi->list, &_path_selectors);
up_write(&_ps_lock);
return r;
}
int dm_unregister_path_selector(struct path_selector_type *pst)
{
struct ps_internal *psi;
down_write(&_ps_lock);
psi = __find_path_selector_type(pst->name);
if (!psi) {
up_write(&_ps_lock);
return -EINVAL;
}
list_del(&psi->list);
up_write(&_ps_lock);
kfree(psi);
return 0;
}
EXPORT_SYMBOL_GPL(dm_register_path_selector);
EXPORT_SYMBOL_GPL(dm_unregister_path_selector);