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dm: path selector use module refcount directly

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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 #1
  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>
This commit is contained in:
Jun'ichi Nomura 2009-04-02 19:55:27 +01:00 committed by Alasdair G Kergon
parent 5642b8a61a
commit aea9058801
1 changed files with 3 additions and 18 deletions
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21
drivers/md/dm-path-selector.c
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@ -17,9 +17,7 @@
struct ps_internal {
struct path_selector_type pst;
struct list_head list;
long use;
};
#define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
@ -45,12 +43,8 @@ static struct ps_internal *get_path_selector(const char *name)
down_read(&_ps_lock);
psi = __find_path_selector_type(name);
if (psi) {
if ((psi->use == 0) && !try_module_get(psi->pst.module))
psi = NULL;
else
psi->use++;
}
if (psi && !try_module_get(psi->pst.module))
psi = NULL;
up_read(&_ps_lock);
return psi;
@ -84,11 +78,7 @@ void dm_put_path_selector(struct path_selector_type *pst)
if (!psi)
goto out;
if (--psi->use == 0)
module_put(psi->pst.module);
BUG_ON(psi->use < 0);
module_put(psi->pst.module);
out:
up_read(&_ps_lock);
}
@ -136,11 +126,6 @@ int dm_unregister_path_selector(struct path_selector_type *pst)
return -EINVAL;
}
if (psi->use) {
up_write(&_ps_lock);
return -ETXTBSY;
}
list_del(&psi->list);
up_write(&_ps_lock);