diff options
| author | Goldwyn Rodrigues <rgoldwyn@suse.com> | 2017-06-20 07:05:46 -0500 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-06-20 07:12:03 -0600 |
| commit | 03a07c92a9ed9938d828ca7f1d11b8bc63a7bb89 (patch) | |
| tree | aced260faa3cdf56d6f1140579ffaf46f8ba9c25 /block/blk-mq.c | |
| parent | a38d1243704f501a4c42de1db1062ff6eba83453 (diff) | |
block: return on congested block device
A new bio operation flag REQ_NOWAIT is introduced to identify bio's
orignating from iocb with IOCB_NOWAIT. This flag indicates
to return immediately if a request cannot be made instead
of retrying.
Stacked devices such as md (the ones with make_request_fn hooks)
currently are not supported because it may block for housekeeping.
For example, an md can have a part of the device suspended.
For this reason, only request based devices are supported.
In the future, this feature will be expanded to stacked devices
by teaching them how to handle the REQ_NOWAIT flags.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.c')
| -rw-r--r-- | block/blk-mq.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index dd276a9e138e..ca03cd4b263f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -293,6 +293,8 @@ static struct request *blk_mq_get_request(struct request_queue *q, data->ctx = blk_mq_get_ctx(q); if (likely(!data->hctx)) data->hctx = blk_mq_map_queue(q, data->ctx->cpu); + if (op & REQ_NOWAIT) + data->flags |= BLK_MQ_REQ_NOWAIT; if (e) { data->flags |= BLK_MQ_REQ_INTERNAL; @@ -1544,6 +1546,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) rq = blk_mq_get_request(q, bio, bio->bi_opf, &data); if (unlikely(!rq)) { __wbt_done(q->rq_wb, wb_acct); + if (bio->bi_opf & REQ_NOWAIT) + bio_wouldblock_error(bio); return BLK_QC_T_NONE; } |