From: Ming Lei <ming.lei@xxxxxxxxxx>
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.
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
[hch: keep the preempt disable confined inside blk_mq_get_tag]
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/blk-mq-tag.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index b526f1f5a3bf3..0cc38883618b9 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -108,6 +108,7 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
unsigned int tag_offset;
int tag;
+ preempt_disable();
data->ctx = blk_mq_get_ctx(data->q);
data->hctx = blk_mq_map_queue(data->q, data->cmd_flags, data->ctx);
tags = blk_mq_tags_from_data(data);
@@ -115,10 +116,8 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
blk_mq_tag_busy(data->hctx);
if (data->flags & BLK_MQ_REQ_RESERVED) {
- if (unlikely(!tags->nr_reserved_tags)) {
- WARN_ON_ONCE(1);
- return BLK_MQ_TAG_FAIL;
- }
+ if (WARN_ON_ONCE(!tags->nr_reserved_tags))
+ goto fail;
bt = &tags->breserved_tags;
tag_offset = 0;
} else {
@@ -131,7 +130,7 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
goto found_tag;
if (data->flags & BLK_MQ_REQ_NOWAIT)
- return BLK_MQ_TAG_FAIL;
+ goto fail;
ws = bt_wait_ptr(bt, data->hctx);
do {
@@ -158,11 +157,13 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
if (tag != -1)
break;
+ preempt_enable();
+
bt_prev = bt;
io_schedule();
-
sbitmap_finish_wait(bt, ws, &wait);
+ preempt_disable();
data->ctx = blk_mq_get_ctx(data->q);
data->hctx = blk_mq_map_queue(data->q, data->cmd_flags,
data->ctx);
@@ -186,7 +187,11 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
sbitmap_finish_wait(bt, ws, &wait);
found_tag:
+ preempt_enable();
return tag + tag_offset;
+fail:
+ preempt_enable();
+ return BLK_MQ_TAG_FAIL;
}
bool __blk_mq_get_driver_tag(struct request *rq)
--
2.26.2
