From aea9058801c0acfa2831af1714da412dfb0018c2 Mon Sep 17 00:00:00 2001 From: Jun'ichi Nomura Date: Thu, 2 Apr 2009 19:55:27 +0100 Subject: [PATCH] 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 #1 dm_put_path_selector+0x4d/0x61 [dm_multipath] Call Trace: [] free_priority_group+0x33/0xb3 [dm_multipath] [] free_multipath+0x31/0x67 [dm_multipath] [] multipath_dtr+0x2d/0x32 [dm_multipath] [] dm_table_destroy+0x64/0xd8 [dm_mod] [] __unbind+0x46/0x4b [dm_mod] [] dm_swap_table+0x60/0x14d [dm_mod] [] dev_suspend+0xfd/0x177 [dm_mod] [] dm_ctl_ioctl+0x24c/0x29c [dm_mod] [] ? get_page_from_freelist+0x49c/0x61d [] ? dev_suspend+0x0/0x177 [dm_mod] [] vfs_ioctl+0x2a/0x77 [] do_vfs_ioctl+0x448/0x4a0 [] sys_ioctl+0x57/0x7a [] system_call_fastpath+0x16/0x1b Cc: stable@kernel.org Signed-off-by: Jun'ichi Nomura Signed-off-by: Alasdair G Kergon --- drivers/md/dm-path-selector.c | 21 +++------------------ 1 file changed, 3 insertions(+), 18 deletions(-) diff --git a/drivers/md/dm-path-selector.c b/drivers/md/dm-path-selector.c index 96ea226..42c04f0 100644 --- a/drivers/md/dm-path-selector.c +++ b/drivers/md/dm-path-selector.c @@ -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); -- 2.7.4