Sachin reports [1] a crash in SLUB __slab_alloc():
BUG: Kernel NULL pointer dereference on read at 0x000073b0
Faulting instruction address: 0xc0000000003d55f4
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
Modules linked in:
CPU: 19 PID: 1 Comm: systemd Not tainted 5.6.0-rc2-next-20200218-autotest #1
NIP: c0000000003d55f4 LR: c0000000003d5b94 CTR: 0000000000000000
REGS: c0000008b37836d0 TRAP: 0300 Not tainted (5.6.0-rc2-next-20200218-autotest)
MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 24004844 XER: 00000000
CFAR: c00000000000dec4 DAR: 00000000000073b0 DSISR: 40000000 IRQMASK: 1
GPR00: c0000000003d5b94 c0000008b3783960 c00000000155d400 c0000008b301f500
GPR04: 0000000000000dc0 0000000000000002 c0000000003443d8 c0000008bb398620
GPR08: 00000008ba2f0000 0000000000000001 0000000000000000 0000000000000000
GPR12: 0000000024004844 c00000001ec52a00 0000000000000000 0000000000000000
GPR16: c0000008a1b20048 c000000001595898 c000000001750c18 0000000000000002
GPR20: c000000001750c28 c000000001624470 0000000fffffffe0 5deadbeef0000122
GPR24: 0000000000000001 0000000000000dc0 0000000000000002 c0000000003443d8
GPR28: c0000008b301f500 c0000008bb398620 0000000000000000 c00c000002287180
NIP [c0000000003d55f4] ___slab_alloc+0x1f4/0x760
LR [c0000000003d5b94] __slab_alloc+0x34/0x60
Call Trace:
[c0000008b3783960] [c0000000003d5734] ___slab_alloc+0x334/0x760 (unreliable)
[c0000008b3783a40] [c0000000003d5b94] __slab_alloc+0x34/0x60
[c0000008b3783a70] [c0000000003d6fa0] __kmalloc_node+0x110/0x490
[c0000008b3783af0] [c0000000003443d8] kvmalloc_node+0x58/0x110
[c0000008b3783b30] [c0000000003fee38] mem_cgroup_css_online+0x108/0x270
[c0000008b3783b90] [c000000000235aa8] online_css+0x48/0xd0
[c0000008b3783bc0] [c00000000023eaec] cgroup_apply_control_enable+0x2ec/0x4d0
[c0000008b3783ca0] [c000000000242318] cgroup_mkdir+0x228/0x5f0
[c0000008b3783d10] [c00000000051e170] kernfs_iop_mkdir+0x90/0xf0
[c0000008b3783d50] [c00000000043dc00] vfs_mkdir+0x110/0x230
[c0000008b3783da0] [c000000000441c90] do_mkdirat+0xb0/0x1a0
[c0000008b3783e20] [c00000000000b278] system_call+0x5c/0x68
This is a PowerPC platform with following NUMA topology:
available: 2 nodes (0-1)
node 0 cpus:
node 0 size: 0 MB
node 0 free: 0 MB
node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
node 1 size: 35247 MB
node 1 free: 30907 MB
node distances:
node 0 1
0: 10 40
1: 40 10
possible numa nodes: 0-31
This only happens with a mmotm patch "mm/memcontrol.c: allocate shrinker_map on
appropriate NUMA node" [2] which effectively calls kmalloc_node for each
possible node. SLUB however only allocates kmem_cache_node on online nodes
with present memory, and relies on node_to_mem_node to return such valid node
for other nodes since commit a561ce00b09e ("slub: fall back to
node_to_mem_node() node if allocating on memoryless node"). This is however not
true in this configuration where the _node_numa_mem_ array is not initialized
for nodes 0 and 2-31, thus it contains zeroes and get_partial() ends up
accessing non-allocated kmem_cache_node.
A related issue was reported by Bharata [3] where a similar PowerPC
configuration, but without patch [2] ends up allocating large amounts of pages
by kmalloc-1k kmalloc-512. This seems to have the same underlying issue with
node_to_mem_node() not behaving as expected, and might probably also lead
to an infinite loop with CONFIG_SLUB_CPU_PARTIAL.
This patch should fix both issues by not relying on node_to_mem_node() anymore
and instead simply falling back to NUMA_NO_NODE, when kmalloc_node(node) is
attempted for a node that's not online or has no pages. Also in case
alloc_slab_page() is reached with a non-online node, fallback as well, until
we have a guarantee that all possible nodes have valid NODE_DATA with proper
zonelist for fallback.
[1] https://lore.kernel.org/linux-next/3381CD91-AB3D-4773-BA04-E7A072A63968@xxxxxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-mm/fff0e636-4c36-ed10-281c-8cdb0687c839@xxxxxxxxxxxxx/
[3] https://lore.kernel.org/linux-mm/20200317092624.GB22538@xxxxxxxxxx/
[4] https://lore.kernel.org/linux-mm/088b5996-faae-8a56-ef9c-5b567125ae54@xxxxxxx/
Reported-by: Sachin Sant <sachinp@xxxxxxxxxxxxxxxxxx>
Reported-by: Bharata B Rao <bharata@xxxxxxxxxxxxx>
Debugged-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Christopher Lameter <cl@xxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Nathan Lynch <nathanl@xxxxxxxxxxxxx>
---
Hi, this is my alternate solution of the SLUB issues to the series [1]. Could
Sachin and Bharata please test whether it fixes the issues?
1) on plain mainline (Bharata) or next (Sachin)
2) the same but with [PATCH 0/3] Offline memoryless cpuless node 0 [2] as I
assume the series was not related to the SLUB issues and will be kept?
Thanks!
[1] https://lore.kernel.org/linux-mm/20200318072810.9735-1-srikar@xxxxxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-mm/20200311110237.5731-1-srikar@xxxxxxxxxxxxxxxxxx/
mm/slub.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 17dc00e33115..4d798cacdae1 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1511,7 +1511,7 @@ static inline struct page *alloc_slab_page(struct kmem_cache *s,
struct page *page;
unsigned int order = oo_order(oo);
- if (node == NUMA_NO_NODE)
+ if (node == NUMA_NO_NODE || !node_online(node))
page = alloc_pages(flags, order);
else
page = __alloc_pages_node(node, flags, order);
@@ -1973,8 +1973,6 @@ static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
if (node == NUMA_NO_NODE)
searchnode = numa_mem_id();
- else if (!node_present_pages(node))
- searchnode = node_to_mem_node(node);
object = get_partial_node(s, get_node(s, searchnode), c, flags);
if (object || node != NUMA_NO_NODE)
@@ -2568,12 +2566,15 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
redo:
if (unlikely(!node_match(page, node))) {
- int searchnode = node;
-
- if (node != NUMA_NO_NODE && !node_present_pages(node))
- searchnode = node_to_mem_node(node);
-
- if (unlikely(!node_match(page, searchnode))) {
+ /*
+ * node_match() false implies node != NUMA_NO_NODE
+ * but if the node is not online or has no pages, just
+ * ignore the constraint
+ */
+ if ((!node_online(node) || !node_present_pages(node))) {
+ node = NUMA_NO_NODE;
+ goto redo;
+ } else {
stat(s, ALLOC_NODE_MISMATCH);
deactivate_slab(s, page, c->freelist, c);
goto new_slab;
--
2.25.1
