https://github.com/torvalds/linux
Revision 20ab67a563f5299c09a234164c372aba5a59add8 authored by Michal Hocko on 03 December 2016, 01:26:45 UTC, committed by Linus Torvalds on 03 December 2016, 02:48:03 UTC
Commit 0a6b76dd23fa ("mm: workingset: make shadow node shrinker memcg aware") has made the workingset shadow nodes shrinker memcg aware. The implementation is not correct though because memcg_kmem_enabled() might become true while we are doing a global reclaim when the sc->memcg might be NULL which is exactly what Marek has seen: BUG: unable to handle kernel NULL pointer dereference at 0000000000000400 IP: [<ffffffff8122d520>] mem_cgroup_node_nr_lru_pages+0x20/0x40 PGD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 60 Comm: kswapd0 Tainted: G O 4.8.10-12.pvops.qubes.x86_64 #1 task: ffff880011863b00 task.stack: ffff880011868000 RIP: mem_cgroup_node_nr_lru_pages+0x20/0x40 RSP: e02b:ffff88001186bc70 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff88001186bd20 RCX: 0000000000000002 RDX: 000000000000000c RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff88001186bc70 R08: 28f5c28f5c28f5c3 R09: 0000000000000000 R10: 0000000000006c34 R11: 0000000000000333 R12: 00000000000001f6 R13: ffffffff81c6f6a0 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff880013c00000(0000) knlGS:ffff880013d00000 CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000400 CR3: 00000000122f2000 CR4: 0000000000042660 Call Trace: count_shadow_nodes+0x9a/0xa0 shrink_slab.part.42+0x119/0x3e0 shrink_node+0x22c/0x320 kswapd+0x32c/0x700 kthread+0xd8/0xf0 ret_from_fork+0x1f/0x40 Code: 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 3b 35 dd eb b1 00 55 48 89 e5 73 2c 89 d2 31 c9 31 c0 4c 63 ce 48 0f a3 ca 73 13 <4a> 8b b4 cf 00 04 00 00 41 89 c8 4a 03 84 c6 80 00 00 00 83 c1 RIP mem_cgroup_node_nr_lru_pages+0x20/0x40 RSP <ffff88001186bc70> CR2: 0000000000000400 ---[ end trace 100494b9edbdfc4d ]--- This patch fixes the issue by checking sc->memcg rather than memcg_kmem_enabled() which is sufficient because shrink_slab makes sure that only memcg aware shrinkers will get non-NULL memcgs and only if memcg_kmem_enabled is true. Fixes: 0a6b76dd23fa ("mm: workingset: make shadow node shrinker memcg aware") Link: http://lkml.kernel.org/r/20161201132156.21450-1-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Reported-by: Marek Marczykowski-Górecki <marmarek@mimuw.edu.pl> Tested-by: Marek Marczykowski-Górecki <marmarek@mimuw.edu.pl> Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Balbir Singh <bsingharora@gmail.com> Cc: <stable@vger.kernel.org> [4.6+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 8dc0f26
Tip revision: 20ab67a563f5299c09a234164c372aba5a59add8 authored by Michal Hocko on 03 December 2016, 01:26:45 UTC
mm: workingset: fix NULL ptr in count_shadow_nodes
mm: workingset: fix NULL ptr in count_shadow_nodes
Tip revision: 20ab67a
File | Mode | Size |
---|---|---|
Documentation | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.cocciconfig | -rw-r--r-- | 59 bytes |
.get_maintainer.ignore | -rw-r--r-- | 31 bytes |
.gitattributes | -rw-r--r-- | 30 bytes |
.gitignore | -rw-r--r-- | 1.3 KB |
.mailmap | -rw-r--r-- | 7.5 KB |
COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 96.0 KB |
Kbuild | -rw-r--r-- | 2.8 KB |
Kconfig | -rw-r--r-- | 252 bytes |
MAINTAINERS | -rw-r--r-- | 373.6 KB |
Makefile | -rw-r--r-- | 57.4 KB |
README | -rw-r--r-- | 17.9 KB |
REPORTING-BUGS | -rw-r--r-- | 7.3 KB |
Computing file changes ...