[34-longterm 032/209] percpu: fix list_head init bug in __percpu_counter_init()

[Paul Gortmaker]

From: Masanori ITOH <itoumsn@xxxxxxxxxxxxx>

  =====================================================================
  | This is a commit scheduled for the next v2.6.34 longterm release. |
  | If you see a problem with using this for longterm, please comment.|
  =====================================================================

commit 8474b591faf3bb0a1e08a60d21d6baac498f15e4 upstream.

WARNING: at lib/list_debug.c:26 __list_add+0x3f/0x81()
Hardware name: Express5800/B120a [N8400-085]
list_add corruption. next->prev should be prev (ffffffff81a7ea00), but was dead000000200200. (next=ffff88080b872d58).
Modules linked in: aoe ipt_MASQUERADE iptable_nat nf_nat autofs4 sunrpc bridge 8021q garp stp llc ipv6 cpufreq_ondemand acpi_cpufreq freq_table dm_round_robin dm_multipath kvm_intel kvm uinput lpfc scsi_transport_fc igb ioatdma scsi_tgt i2c_i801 i2c_core dca iTCO_wdt iTCO_vendor_support pcspkr shpchp megaraid_sas [last unloaded: aoe]
Pid: 54, comm: events/3 Tainted: G        W  2.6.34-vanilla1 #1
Call Trace:
[<ffffffff8104bd77>] warn_slowpath_common+0x7c/0x94
[<ffffffff8104bde6>] warn_slowpath_fmt+0x41/0x43
[<ffffffff8120fd2e>] __list_add+0x3f/0x81
[<ffffffff81212a12>] __percpu_counter_init+0x59/0x6b
[<ffffffff810d8499>] bdi_init+0x118/0x17e
[<ffffffff811f2c50>] blk_alloc_queue_node+0x79/0x143
[<ffffffff811f2d2b>] blk_alloc_queue+0x11/0x13
[<ffffffffa02a931d>] aoeblk_gdalloc+0x8e/0x1c9 [aoe]
[<ffffffffa02aa655>] aoecmd_sleepwork+0x25/0xa8 [aoe]
[<ffffffff8106186c>] worker_thread+0x1a9/0x237
[<ffffffffa02aa630>] ? aoecmd_sleepwork+0x0/0xa8 [aoe]
[<ffffffff81065827>] ? autoremove_wake_function+0x0/0x39
[<ffffffff810616c3>] ? worker_thread+0x0/0x237
[<ffffffff810653ad>] kthread+0x7f/0x87
[<ffffffff8100aa24>] kernel_thread_helper+0x4/0x10
[<ffffffff8106532e>] ? kthread+0x0/0x87
[<ffffffff8100aa20>] ? kernel_thread_helper+0x0/0x10

It's because there is no initialization code for a list_head contained in
the struct backing_dev_info under CONFIG_HOTPLUG_CPU, and the bug comes up
when block device drivers calling blk_alloc_queue() are used.  In case of
me, I got them by using aoe.

Signed-off-by: Masanori Itoh <itoumsn@xxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 lib/percpu_counter.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index aeaa6d7..9d94212 100644
--- a/lib/percpu_counter.c
+++ b/lib/percpu_counter.c
@@ -76,6 +76,7 @@ int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
 	if (!fbc->counters)
 		return -ENOMEM;
 #ifdef CONFIG_HOTPLUG_CPU
+	INIT_LIST_HEAD(&fbc->list);
 	mutex_lock(&percpu_counters_lock);
 	list_add(&fbc->list, &percpu_counters);
 	mutex_unlock(&percpu_counters_lock);
-- 
1.7.4.4

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