<html><head><meta http-equiv="content-type" content="text/html; charset=us-ascii"><style>body { line-height: 1.5; }body { font-size: 10.5pt; font-family: 'Segoe UI'; color: rgb(0, 0, 0); line-height: 1.5; }</style></head><body> <div><span style="font-family: "" segoe="" ui'";="" font-size:="" 14px;="" color:="" rgb(0,="" 0,="" 0);="" background-color:="" rgba(0,="" font-weight:="" normal;="" font-style:="" normal;text-decoration:="" none;'="">We got a NULL pointer exception when testing the two concurrent "vgchange -ay -K <vg name>".</div><div><span style="font-family: "" segoe="" ui'";="" font-size:="" 14px;="" color:="" rgb(0,="" 0,="" 0);="" background-color:="" rgba(0,="" font-weight:="" normal;="" font-style:="" normal;text-decoration:="" none;'="">panic call trace: PID: 25992 TASK: ffff883cd7d23500 CPU: 4 COMMAND: "vgchange" #0 [ffff883cd743d600] machine_kexec at ffffffff81038fa9 0000001 [ffff883cd743d660] crash_kexec at ffffffff810c5992 0000002 [ffff883cd743d730] oops_end at ffffffff81515c90 0000003 [ffff883cd743d760] no_context at ffffffff81049f1b 0000004 [ffff883cd743d7b0] __bad_area_nosemaphore at ffffffff8104a1a5 0000005 [ffff883cd743d800] bad_area at ffffffff8104a2ce 0000006 [ffff883cd743d830] __do_page_fault at ffffffff8104aa6f 0000007 [ffff883cd743d950] do_page_fault at ffffffff81517bae 0000008 [ffff883cd743d980] page_fault at ffffffff81514f95 [exception RIP: kmem_cache_alloc+108] RIP: ffffffff8116ef3c RSP: ffff883cd743da38 RFLAGS: 00010046 RAX: 0000000000000004 RBX: ffffffff81121b90 RCX: ffff881bf1e78cc0 RDX: 0000000000000000 RSI: 00000000000000d0 RDI: 0000000000000000 RBP: ffff883cd743da68 R8: ffff881bf1a4eb00 R9: 0000000080042000 R10: 0000000000002000 R11: 0000000000000000 R12: 00000000000000d0 R13: 0000000000000000 R14: 00000000000000d0 R15: 0000000000000246 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 0000009 [ffff883cd743da70] mempool_alloc_slab at ffffffff81121ba5 0000010 [ffff883cd743da80] mempool_create_node at ffffffff81122083 0000011 [ffff883cd743dad0] mempool_create at ffffffff811220f4 0000012 [ffff883cd743dae0] pool_ctr at ffffffffa08de049 [dm_thin_pool] 0000013 [ffff883cd743dbd0] dm_table_add_target at ffffffffa0005f2f [dm_mod] 0000014 [ffff883cd743dc30] table_load at ffffffffa0008ba9 [dm_mod] 0000015 [ffff883cd743dc90] ctl_ioctl at ffffffffa0009dc4 [dm_mod] this bug's scence is as follows: process A(vgchange -ay -K): a. send DM_LIST_VERSIONS_CMD ioctl; b. pool_target not registered; c. modprobe dm_thin_pool and wait until end. process B(vgchange -ay -K): a. send DM_LIST_VERSIONS_CMD ioctl; b. pool_target registered; c. table_load->dm_table_add_target->pool_ctr; d. _new_mapping_cache is NULL and panic. note: 1. process A and process B are two concurrent processes. 2. pool_target can be detected by process B but _new_mapping_cache initialization has not ended. All that we need do is to ensure pool_target registering ops is the last ops in dm_thin_init. Signed-off-by: monty <monty_pavel@sina.com> --- drivers/md/dm-thin.c | 22 ++++++++++------------ 1 files changed, 10 insertions(+), 12 deletions(-) diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 89e5dff..f91d771 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -4355,30 +4355,28 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits) static int __init dm_thin_init(void) { - int r; + int r = -ENOMEM; pool_table_init(); + _new_mapping_cache = KMEM_CACHE(dm_thin_new_mapping, 0); + if (!_new_mapping_cache) + return r; + r = dm_register_target(&thin_target); if (r) - return r; + goto bad_new_mapping_cache; r = dm_register_target(&pool_target); if (r) - goto bad_pool_target; - - r = -ENOMEM; - - _new_mapping_cache = KMEM_CACHE(dm_thin_new_mapping, 0); - if (!_new_mapping_cache) - goto bad_new_mapping_cache; + goto bad_thin_target; return 0; -bad_new_mapping_cache: - dm_unregister_target(&pool_target); -bad_pool_target: +bad_thin_target: dm_unregister_target(&thin_target); +bad_new_mapping_cache: + kmem_cache_destroy(_new_mapping_cache); return r; } -- 1.7.1</div> </body></html>