Disable preempt for a little while during allocating request tag, so
request's tag(internal tag) is always allocated on the cpu of data->ctx,
prepare for improving to handle cpu hotplug during allocating request.
In the following patch, hctx->state will be checked to see if it becomes
inactive which is always set on the last CPU of hctx->cpumask.
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: John Garry <john.garry@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-mq-tag.c | 4 ++++
block/blk-mq.c | 4 ++++
block/blk-mq.h | 1 +
3 files changed, 9 insertions(+)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index c27c6dfc7d36..0ae79ca6e2da 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -152,11 +152,15 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
if (tag != -1)
break;
+ if (data->preempt_disabled)
+ preempt_enable();
bt_prev = bt;
io_schedule();
sbitmap_finish_wait(bt, ws, &wait);
+ if (data->preempt_disabled)
+ preempt_disable();
data->ctx = blk_mq_get_ctx(data->q);
data->hctx = blk_mq_map_queue(data->q, data->cmd_flags,
data->ctx);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 151b63b1f88b..18999198a37f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -365,6 +365,9 @@ static struct request *blk_mq_get_request(struct request_queue *q,
data->q = q;
WARN_ON_ONCE(data->ctx || data->hctx);
+
+ preempt_disable();
+ data->preempt_disabled = true;
data->ctx = blk_mq_get_ctx(q);
data->hctx = blk_mq_map_queue(q, data->cmd_flags, data->ctx);
if (data->cmd_flags & REQ_NOWAIT)
@@ -387,6 +390,7 @@ static struct request *blk_mq_get_request(struct request_queue *q,
}
tag = blk_mq_get_tag(data);
+ preempt_enable();
if (tag == BLK_MQ_TAG_FAIL) {
data->ctx = NULL;
data->hctx = NULL;
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 10bfdfb494fa..5ebc8d8d5a54 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -152,6 +152,7 @@ struct blk_mq_alloc_data {
blk_mq_req_flags_t flags;
unsigned int shallow_depth;
unsigned int cmd_flags;
+ bool preempt_disabled;
/* input & output parameter */
struct blk_mq_ctx *ctx;
--
2.25.2
