On Fri, Apr 14, 2017 at 07:02:54AM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> A new bio operation flag REQ_NOWAIT is introduced to identify bio's
s/bio/block/
> @@ -1232,6 +1232,11 @@ static struct request *get_request(struct request_queue *q, unsigned int op,
> if (!IS_ERR(rq))
> return rq;
>
> + if (bio && (bio->bi_opf & REQ_NOWAIT)) {
> + blk_put_rl(rl);
> + return ERR_PTR(-EAGAIN);
> + }
Please check the op argument instead of touching bio.
> + if (bio->bi_opf & REQ_NOWAIT) {
> + if (!blk_queue_nowait(q)) {
> + err = -EOPNOTSUPP;
> + goto end_io;
> + }
> + if (!(bio->bi_opf & REQ_SYNC)) {
I don't understand this check at all..
> + if (unlikely(!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT)))
Please break lines after 80 characters.
> @@ -119,6 +119,9 @@ struct request *blk_mq_sched_get_request(struct request_queue *q,
> if (likely(!data->hctx))
> data->hctx = blk_mq_map_queue(q, data->ctx->cpu);
>
> + if (bio && (bio->bi_opf & REQ_NOWAIT))
> + data->flags |= BLK_MQ_REQ_NOWAIT;
Check the op flag again here.
> +++ b/block/blk-mq.c
> @@ -1538,6 +1538,8 @@ 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->bi_opf & REQ_NOWAIT))
> + bio_wouldblock_error(bio);
bio iѕ dereferences unconditionally above, so you can do the same.
> @@ -1662,6 +1664,8 @@ static blk_qc_t blk_sq_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->bi_opf & REQ_NOWAIT))
> + bio_wouldblock_error(bio);
Same here. Although blk_sq_make_request is gone anyway in the current
block tree..
> + /* Request queue supports BIO_NOWAIT */
> + queue_flag_set_unlocked(QUEUE_FLAG_NOWAIT, q);
BIO_NOWAIT is gone. And the comment would not be needed if the
flag had a more descriptive name, e.g. QUEUE_FLAG_NOWAIT_SUPPORT.
And I think all request based drivers should set the flag implicitly
as ->queuecommand can't sleep, and ->queue_rq only when it's always
offloaded to a workqueue when the BLK_MQ_F_BLOCKING flag is set.
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -480,8 +480,12 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio)
> unsigned i;
> int err;
>
> - if (bio->bi_error)
> - dio->io_error = -EIO;
> + if (bio->bi_error) {
> + if (bio->bi_opf & REQ_NOWAIT)
> + dio->io_error = -EAGAIN;
> + else
> + dio->io_error = -EIO;
> + }
Huh? Once REQ_NOWAIT is set all errors are -EAGAIN?
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