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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
parent74c450521dd8d245b982da62592a18aa6f88b045 (diff)
downloadop-kernel-dev-e167dfb53cb85fde7b15f644e9dbef7ba31896b6.zip
op-kernel-dev-e167dfb53cb85fde7b15f644e9dbef7ba31896b6.tar.gz
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>
-rw-r--r--block/blk-mq.c7
-rw-r--r--include/linux/blk-mq.h1
2 files changed, 7 insertions, 1 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 7e53038..b355b59 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,
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index be01d7a..c3b64ec 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -146,6 +146,7 @@ enum {
BLK_MQ_F_TAG_SHARED = 1 << 1,
BLK_MQ_F_SG_MERGE = 1 << 2,
BLK_MQ_F_SYSFS_UP = 1 << 3,
+ BLK_MQ_F_DEFER_ISSUE = 1 << 4,
BLK_MQ_S_STOPPED = 0,
BLK_MQ_S_TAG_ACTIVE = 1,
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