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authorJens Axboe <axboe@fb.com>2014-10-29 11:18:26 -0600
committerJens Axboe <axboe@fb.com>2014-10-29 11:18:26 -0600
commite167dfb53cb85fde7b15f644e9dbef7ba31896b6 (patch)
treebaf22faa1d3de6c2a70faeacc0599f01f5469a2d /block
parent74c450521dd8d245b982da62592a18aa6f88b045 (diff)
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.c7
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,