Re: [BUG] MD/RAID1 hung forever on freeze_array

[NeilBrown <neilb@suse.com>]

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On Mon, Dec 19 2016, Jinpu Wang wrote:

> Hi Neil,
>
> After apply the patch below, it paniced during boot in
> generic_make_request-> bio_list_pop.
> Looks related to you do bio_list_init(&bio_list_on_stack); again.
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index 14d7c0740dc0..3436b6fc3ef8 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -2036,10 +2036,31 @@ blk_qc_t generic_make_request(struct bio *bio)
>>                 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
>>
>>                 if (likely(blk_queue_enter(q, false) == 0)) {
>> +                       struct bio_list hold;
>> +                       struct bio_list lower, same;
>> +
>> +                       /* Create a fresh bio_list for all subordinate requests */
>> +                       bio_list_merge(&hold, &bio_list_on_stack);

This is the problem.  'hold' hasn't been initialised.
We could either do:
  bio_list_init(&hold);
  bio_list_merge(&hold, &bio_list_on_stack);
or just
  hold = bio_list_on_stack;


You didn't find 'hold' to be necessary in your testing, but I think that
is more complex arrangements it could make an important difference.

Thanks,
NeilBrown


>> +                       bio_list_init(&bio_list_on_stack); ??? maybe init hold, and then merge bio_list_on_stack?
>>                         ret = q->make_request_fn(q, bio);
>>
>>                         blk_queue_exit(q);

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