Re: Kernel crashes after 529262d56dbe "block: remove ->poll_fn"
From: Jens Axboe
Date: Wed Dec 05 2018 - 08:39:32 EST
On 12/5/18 6:20 AM, Jens Axboe wrote:
> On 12/5/18 6:05 AM, Kirill Tkhai wrote:
>> On 05.12.2018 15:45, Jens Axboe wrote:
>>> On 12/5/18 5:19 AM, Kirill Tkhai wrote:
>>>> Hi,
>>>>
>>>> commit 529262d56dbe from today linux-next makes my kernel crash:
>>>>
>>>> Author: Christoph Hellwig <hch@xxxxxx>
>>>> Date: Sun Dec 2 17:46:26 2018 +0100
>>>>
>>>> block: remove ->poll_fn
>>>>
>>>> Traceback is below, config and reproducer (not minimal, just a random one populating swap) are attached.
>>>>
>>>> [ 29.097612] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
>>>> [ 29.098730] #PF error: [INSTR]
>>>> [ 29.099104] PGD 0 P4D 0
>>>> [ 29.099425] Oops: 0010 [#1] PREEMPT SMP
>>>> [ 29.099879] CPU: 3 PID: 925 Comm: bash Not tainted 4.20.0-rc5-next-20181205+ #244
>>>> [ 29.100658] RIP: 0010: (null)
>>>> [ 29.101100] Code: Bad RIP value.
>>>> [ 29.101480] RSP: 0000:ffffc9000023fb80 EFLAGS: 00010202
>>>> [ 29.102061] RAX: ffffffff8182d0e0 RBX: ffff88807ceee000 RCX: 0000000000000000
>>>> [ 29.102818] RDX: ffff88807d560f40 RSI: 0000000000000000 RDI: ffff88807ceee000
>>>> [ 29.103661] RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000002000
>>>> [ 29.104560] R10: 00000000ffffffff R11: ffff88807c854150 R12: 0000000000000000
>>>> [ 29.105458] R13: 0000000000000002 R14: ffff88807d7236c0 R15: ffffc9000023fe20
>>>> [ 29.106438] FS: 00007faba91d7740(0000) GS:ffff88807db80000(0000) knlGS:0000000000000000
>>>> [ 29.107304] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [ 29.107917] CR2: ffffffffffffffd6 CR3: 000000007a172000 CR4: 00000000000006a0
>>>> [ 29.109401] Call Trace:
>>>> [ 29.110017] ? blk_poll+0x27c/0x340
>>>> [ 29.110691] ? submit_bio+0x40/0x120
>>>> [ 29.111278] ? swap_readpage+0x148/0x190
>>>> [ 29.111924] ? read_swap_cache_async+0x53/0x60
>>>> [ 29.112670] ? swap_cluster_readahead+0x231/0x2b0
>>>> [ 29.113310] ? swapin_readahead+0x2ce/0x400
>>>> [ 29.113878] ? pagecache_get_page+0x2b/0x210
>>>> [ 29.114416] ? do_swap_page+0x42c/0x800
>>>> [ 29.114919] ? __handle_mm_fault+0x544/0xdd0
>>>> [ 29.115455] ? handle_mm_fault+0x112/0x230
>>>> [ 29.115978] ? __do_page_fault+0x196/0x410
>>>> [ 29.116501] ? __put_user_4+0x19/0x20
>>>> [ 29.116990] ? page_fault+0x5/0x20
>>>> [ 29.117451] ? page_fault+0x1b/0x20
>>>> [ 29.117925] CR2: 0000000000000000
>>>> [ 29.118472] ---[ end trace 0faa4ddc190b41fa ]---
>>>
>>> Can you try this? The swap read-in poll attempts looks totally
>>> incorrect.
>>>
>>>
>>> diff --git a/mm/page_io.c b/mm/page_io.c
>>> index 5bdfd21c1bd9..f3455f9f8dc7 100644
>>> --- a/mm/page_io.c
>>> +++ b/mm/page_io.c
>>> @@ -401,6 +401,8 @@ int swap_readpage(struct page *page, bool synchronous)
>>> get_task_struct(current);
>>> bio->bi_private = current;
>>> bio_set_op_attrs(bio, REQ_OP_READ, 0);
>>> + if (synchronous)
>>> + bio->bi_opf |= REQ_HIPRI;
>>> count_vm_event(PSWPIN);
>>> bio_get(bio);
>>> qc = submit_bio(bio);
>>> @@ -411,7 +413,7 @@ int swap_readpage(struct page *page, bool synchronous)
>>> break;
>>>
>>> if (!blk_poll(disk->queue, qc, true))
>>> - break;
>>> + io_schedule();
>>> }
>>> __set_current_state(TASK_RUNNING);
>>> bio_put(bio);
>>
>> Still crashes:
>
> What device is this?
This might also help...
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 0b3874bdbc6a..81f1b105946b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -606,8 +606,7 @@ struct request_queue {
(1 << QUEUE_FLAG_ADD_RANDOM))
#define QUEUE_FLAG_MQ_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
- (1 << QUEUE_FLAG_SAME_COMP) | \
- (1 << QUEUE_FLAG_POLL))
+ (1 << QUEUE_FLAG_SAME_COMP))
void blk_queue_flag_set(unsigned int flag, struct request_queue *q);
void blk_queue_flag_clear(unsigned int flag, struct request_queue *q);
--
Jens Axboe