[PATCH] percpu: fix bootmem error handling in pcpu_page_first_chunk()

[Tejun Heo <tj@kernel.org>]

Applied to percpu/for-3.12-fixes with the if conditional flipped.

Thanks!

----- 8< ------
>From f851c8d8583891a6e0a447b539db3c39a4f5d43d Mon Sep 17 00:00:00 2001
From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Date: Tue, 17 Sep 2013 16:57:34 +0200

If memory allocation of in pcpu_embed_first_chunk() fails, the
allocated memory is not released correctly. In the release loop also
the non-allocated elements are released which leads to the following
kernel BUG on systems with very little memory:

[    0.000000] kernel BUG at mm/bootmem.c:307!
[    0.000000] illegal operation: 0001 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 3.10.0 #22
[    0.000000] task: 0000000000a20ae0 ti: 0000000000a08000 task.ti: 0000000000a08000
[    0.000000] Krnl PSW : 0400000180000000 0000000000abda7a (__free+0x116/0x154)
[    0.000000]            R:0 T:1 IO:0 EX:0 Key:0 M:0 W:0 P:0 AS:0 CC:0 PM:0 EA:3
...
[    0.000000]  [<0000000000abdce2>] mark_bootmem_node+0xde/0xf0
[    0.000000]  [<0000000000abdd9c>] mark_bootmem+0xa8/0x118
[    0.000000]  [<0000000000abcbba>] pcpu_embed_first_chunk+0xe7a/0xf0c
[    0.000000]  [<0000000000abcc96>] setup_per_cpu_areas+0x4a/0x28c

To fix the problem now only allocated elements are released. This then
leads to the correct kernel panic:

[    0.000000] Kernel panic - not syncing: Failed to initialize percpu areas.
...
[    0.000000] Call Trace:
[    0.000000] ([<000000000011307e>] show_trace+0x132/0x150)
[    0.000000]  [<0000000000113160>] show_stack+0xc4/0xd4
[    0.000000]  [<00000000007127dc>] dump_stack+0x74/0xd8
[    0.000000]  [<00000000007123fe>] panic+0xea/0x264
[    0.000000]  [<0000000000b14814>] setup_per_cpu_areas+0x5c/0x28c

tj: Flipped if conditional so that it doesn't need "continue".

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---
 mm/percpu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index 8c8e08f..0d10def 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1706,8 +1706,9 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
 
 out_free_areas:
 	for (group = 0; group < ai->nr_groups; group++)
-		free_fn(areas[group],
-			ai->groups[group].nr_units * ai->unit_size);
+		if (areas[group])
+			free_fn(areas[group],
+				ai->groups[group].nr_units * ai->unit_size);
 out_free:
 	pcpu_free_alloc_info(ai);
 	if (areas)
-- 
1.8.3.1