On Thu, Mar 16, 2017 at 10:33 PM, Jens Axboe <axboe@xxxxxxxxx> wrote:
> On 03/15/2017 03:51 PM, Goldwyn Rodrigues wrote:
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index 0eeb99e..2e5cba2 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -2014,7 +2019,7 @@ blk_qc_t generic_make_request(struct bio *bio)
>> do {
>> struct request_queue *q = bdev_get_queue(bio->bi_bdev);
>>
>> - if (likely(blk_queue_enter(q, false) == 0)) {
>> + if (likely(blk_queue_enter(q, bio_flagged(bio, BIO_NOWAIT)) == 0)) {
>> struct bio_list hold;
>> struct bio_list lower, same;
>>
>> @@ -2040,7 +2045,10 @@ blk_qc_t generic_make_request(struct bio *bio)
>> bio_list_merge(&bio_list_on_stack, &same);
>> bio_list_merge(&bio_list_on_stack, &hold);
>> } else {
>> - bio_io_error(bio);
>> + if (unlikely(bio_flagged(bio, BIO_NOWAIT)))
>> + bio_wouldblock_error(bio);
>> + else
>> + bio_io_error(bio);
>
> This doesn't look right. What if the queue is dying, and BIO_NOWAIT just
> happened to be set?
>
> And you're missing wbt_wait() as well as a blocking point. Ditto in
> blk-mq.
There are also tons of block points in dm/md/bcache, which need to be
considered or be documented at least, :-)
Thanks,
Ming Lei
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