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.
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 159187a..942ce8c 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1518,6 +1518,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
> rq = blk_mq_sched_get_request(q, bio, bio->bi_opf, &data);
> if (unlikely(!rq)) {
> __wbt_done(q->rq_wb, wb_acct);
> + if (bio && bio_flagged(bio, BIO_NOWAIT))
> + bio_wouldblock_error(bio);
> return BLK_QC_T_NONE;
> }
>
This seems a little fragile now, since not both paths free the bio.
--
Jens Axboe
