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| author | Jens Axboe <axboe@fb.com> | 2014-10-29 11:18:26 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2014-10-29 11:18:26 -0600 |
| commit | e167dfb53cb85fde7b15f644e9dbef7ba31896b6 (patch) | |
| tree | baf22faa1d3de6c2a70faeacc0599f01f5469a2d /block | |
| parent | 74c450521dd8d245b982da62592a18aa6f88b045 (diff) | |
| download | lwn-e167dfb53cb85fde7b15f644e9dbef7ba31896b6.tar.gz lwn-e167dfb53cb85fde7b15f644e9dbef7ba31896b6.zip | |
blk-mq: add BLK_MQ_F_DEFER_ISSUE support flag
Drivers can now tell blk-mq if they take advantage of the deferred
issue through 'last' or not. If they do, don't do queue-direct
for sync IO. This is a preparation patch for the nvme conversion.
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-mq.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 7e5303820452..b355b5957cd7 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1172,7 +1172,12 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio) goto run_queue; } - if (is_sync) { + /* + * If the driver supports defer issued based on 'last', then + * queue it up like normal since we can potentially save some + * CPU this way. + */ + if (is_sync && !(data.hctx->flags & BLK_MQ_F_DEFER_ISSUE)) { struct blk_mq_queue_data bd = { .rq = rq, .list = NULL, |