Commit 01e99aeca39796003 ("blk-mq: insert passthrough request into
hctx->dispatch directly") gives high priority to passthrough requests and
bypass underlying IO scheduler. But as we allocate tag for such request it
still runs io-scheduler's callback limit_depth, while we really want is to
give full sbitmap-depth capabity to such request for acquiring available
tag.
blktrace shows PC requests(dmraid -s -c -i) hit bfq's limit_depth:
8,0 2 0 0.000000000 39952 1,0 m N bfq [bfq_limit_depth] wr_busy 0 sync 0 depth 8
8,0 2 1 0.000008134 39952 D R 4 [dmraid]
8,0 2 2 0.000021538 24 C R [0]
8,0 2 0 0.000035442 39952 1,0 m N bfq [bfq_limit_depth] wr_busy 0 sync 0 depth 8
8,0 2 3 0.000038813 39952 D R 24 [dmraid]
8,0 2 4 0.000044356 24 C R [0]
This patch introduce a new wrapper to make code not that ugly.
Signed-off-by: Lin Feng <linf@xxxxxxxxxx>
---
block/blk-mq.c | 3 ++-
include/linux/blkdev.h | 6 ++++++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index d4d7c1caa439..927189a55575 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -361,11 +361,12 @@ static struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data)
if (e) {
/*
- * Flush requests are special and go directly to the
+ * Flush/passthrough requests are special and go directly to the
* dispatch list. Don't include reserved tags in the
* limiting, as it isn't useful.
*/
if (!op_is_flush(data->cmd_flags) &&
+ !blk_op_is_passthrough(data->cmd_flags) &&
e->type->ops.limit_depth &&
!(data->flags & BLK_MQ_REQ_RESERVED))
e->type->ops.limit_depth(data->cmd_flags, data);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 158aefae1030..0d81eed39833 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -272,6 +272,12 @@ static inline bool bio_is_passthrough(struct bio *bio)
return blk_op_is_scsi(op) || blk_op_is_private(op);
}
+static inline bool blk_op_is_passthrough(unsigned int op)
+{
+ return (blk_op_is_scsi(op & REQ_OP_MASK) ||
+ blk_op_is_private(op & REQ_OP_MASK));
+}
+
static inline unsigned short req_get_ioprio(struct request *req)
{
return req->ioprio;
--
2.30.2
