On 6/28/18 8:42 AM, Michael Ellerman wrote:
> Kent, Jens,
>
> This looks like it might be related to the recent bioset changes?
>
> cheers
>
> Abdul Haleem <abdhalee@xxxxxxxxxxxxxxxxxx> writes:
>> On Tue, 2018-06-26 at 23:36 +1000, Michael Ellerman wrote:
>>> Abdul Haleem <abdhalee@xxxxxxxxxxxxxxxxxx> writes:
> ...
>> I was able to reproduce again with slub_debug=FZP and DEBUG_INFO enabled
>> on 4.17.0-rc7-next-20180601, but not much traces other than the Oops stack trace
>
> Are you still testing on that revision? It's nearly a month old.
>
> Please try to reproduce on mainline or today's linux-next.
>
>
>> the faulty instruction points to below code path :
>>
>> gdb -batch vmlinux -ex 'list *(0xc000000000304fe0)'
>> 0xc000000000304fe0 is in kmem_cache_free (mm/slab.h:231).
>> 226 }
>> 227
>> 228 static inline bool slab_equal_or_root(struct kmem_cache *s,
>> 229 struct kmem_cache *p)
>> 230 {
>> 231 return p == s || p == s->memcg_params.root_cache;
>> 232 }
>
> And s is NULL.
>
> Called via:
> kmem_cache_free+0x210/0x2a0
> mempool_free_slab+0x24/0x40
> mempool_exit+0x50/0x90
> bioset_exit+0x40/0x1d0
> dm_io_client_destroy+0x2c/0x50
> dm_bufio_client_destroy+0x1fc/0x2d0 [dm_bufio]
> persistent_read_metadata+0x430/0x660 [dm_snapshot]
> snapshot_ctr+0x5c8/0x7a0 [dm_snapshot]
> dm_table_add_target+0x19c/0x3c0
> table_load+0x104/0x450
> ctl_ioctl+0x1f8/0x570
> dm_ctl_ioctl+0x18/0x30
> do_vfs_ioctl+0xcc/0x9e0
> ksys_ioctl+0x5c/0xe0
> sys_ioctl+0x20/0x80
> system_call+0x58/0x6c
>
> So looks like we did:
>
> kmem_cache_free(NULL
>
> Probably a bad error path that frees before the cache has been allocated.
>
> mempool_init_node() calls mempool_exit() on a partially initialised
> mempool, which looks fishy, though you're not hitting that patch AFAICS.
The slab cache is setup elsewhere, it's pending_cache. So if pending_cache
is NULL, then yeah and exit there will barf. I'd try something like the
below, but from the trace, we already basically see the path.
diff --git a/include/linux/mempool.h b/include/linux/mempool.h
index 0c964ac107c2..ebfa2f89ffdd 100644
--- a/include/linux/mempool.h
+++ b/include/linux/mempool.h
@@ -59,6 +59,7 @@ void mempool_free_slab(void *element, void *pool_data);
static inline int
mempool_init_slab_pool(mempool_t *pool, int min_nr, struct kmem_cache *kc)
{
+ BUG_ON(!kc);
return mempool_init(pool, min_nr, mempool_alloc_slab,
mempool_free_slab, (void *) kc);
}
diff --git a/mm/mempool.c b/mm/mempool.c
index b54f2c20e5e0..060f44acd0df 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -508,7 +508,9 @@ EXPORT_SYMBOL(mempool_alloc_slab);
void mempool_free_slab(void *element, void *pool_data)
{
struct kmem_cache *mem = pool_data;
- kmem_cache_free(mem, element);
+
+ if (!WARN_ON(!mem))
+ kmem_cache_free(mem, element);
}
EXPORT_SYMBOL(mempool_free_slab);
--
Jens Axboe
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