[PATCH v2 1/2] mm: Uncharge poisoned pages

[Laurent Dufour]

When page are poisoned, they should be uncharged from the root memory
cgroup.

This is required to avoid a BUG raised when the page is onlined back:
BUG: Bad page state in process mem-on-off-test  pfn:7ae3b
page:f000000001eb8ec0 count:0 mapcount:0 mapping:          (null)
index:0x1
flags: 0x3ffff800200000(hwpoison)
raw: 003ffff800200000 0000000000000000 0000000000000001
00000000ffffffff
raw: 5deadbeef0000100 5deadbeef0000200 0000000000000000
c0000007fe055800
page dumped because: page still charged to cgroup
page->mem_cgroup:c0000007fe055800
Modules linked in: pseries_rng rng_core vmx_crypto virtio_balloon
ip_tables x_tables autofs4 virtio_blk virtio_net virtio_pci
virtio_ring virtio
CPU: 34 PID: 5946 Comm: mem-on-off-test Tainted: G    B 4.11.0-rc7-hwp
Call Trace:
[c0000007e4a737f0] [c000000000958e8c] dump_stack+0xb0/0xf0
(unreliable)
[c0000007e4a73830] [c00000000021588c] bad_page+0x11c/0x190
[c0000007e4a738c0] [c00000000021757c] free_pcppages_bulk+0x46c/0x600
[c0000007e4a73990] [c00000000021924c] free_hot_cold_page+0x2ec/0x320
[c0000007e4a739e0] [c0000000002a6440] generic_online_page+0x50/0x70
[c0000007e4a73a10] [c0000000002a6184] online_pages_range+0x94/0xe0
[c0000007e4a73a70] [c00000000005a2b0] walk_system_ram_range+0xe0/0x120
[c0000007e4a73ac0] [c0000000002cce44] online_pages+0x2b4/0x6b0
[c0000007e4a73b60] [c000000000600558] memory_subsys_online+0x218/0x270
[c0000007e4a73bf0] [c0000000005dec84] device_online+0xb4/0x110
[c0000007e4a73c30] [c000000000600f00] store_mem_state+0xc0/0x190
[c0000007e4a73c70] [c0000000005da1d4] dev_attr_store+0x34/0x60
[c0000007e4a73c90] [c000000000377c70] sysfs_kf_write+0x60/0xa0
[c0000007e4a73cb0] [c0000000003769fc] kernfs_fop_write+0x16c/0x240
[c0000007e4a73d00] [c0000000002d1b0c] __vfs_write+0x3c/0x1b0
[c0000007e4a73d90] [c0000000002d34dc] vfs_write+0xcc/0x230
[c0000007e4a73de0] [c0000000002d50e0] SyS_write+0x60/0x110
[c0000007e4a73e30] [c00000000000b760] system_call+0x38/0xfc

Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
 mm/memory-failure.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 27f7210e7fab..22bd22eb25cb 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -529,6 +529,9 @@ static const char * const action_page_types[] = {
  */
 static int delete_from_lru_cache(struct page *p)
 {
+	if (memcg_kmem_enabled())
+		memcg_kmem_uncharge(p, 0);
+
 	if (!isolate_lru_page(p)) {
 		/*
 		 * Clear sensible page flags, so that the buddy system won't
-- 
2.7.4