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Subject[PATCH V5 3/6] blk-mq: fix issue directly case when q is stopped or quiesced
Date
When try to issue request directly, if the queue is stopped or
quiesced, 'bypass' will be ignored and return BLK_STS_OK to caller
to avoid it dispatch request again. Then the request will be
inserted with blk_mq_sched_insert_request. This is not correct
for dm-rq case where we should avoid to pass through the underlying
path's io scheduler.

To fix it, add new mq_issue_decision entry MQ_ISSUE_INSERT_DISPATCH
for above case where the request need to be inserted forcibly.
And use blk_mq_request_bypass_insert to insert the request into
hctx->dispatch directly.

Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
---
block/blk-mq.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 48b7a7c..f54c092 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1768,12 +1768,13 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,

enum mq_issue_decision {
MQ_ISSUE_INSERT_QUEUE,
+ MQ_ISSUE_INSERT_DISPATCH,
MQ_ISSUE_END_REQUEST,
MQ_ISSUE_DO_NOTHING,
};

static inline enum mq_issue_decision
- blk_mq_make_dicision(blk_status_t ret, bool bypass)
+ blk_mq_make_dicision(blk_status_t ret, bool bypass, bool force)
{
enum mq_issue_decision dec;

@@ -1783,7 +1784,10 @@ static inline enum mq_issue_decision
break;
case BLK_STS_DEV_RESOURCE:
case BLK_STS_RESOURCE:
- dec = bypass ? MQ_ISSUE_DO_NOTHING : MQ_ISSUE_INSERT_QUEUE;
+ if (force)
+ dec = bypass ? MQ_ISSUE_INSERT_DISPATCH : MQ_ISSUE_INSERT_QUEUE;
+ else
+ dec = bypass ? MQ_ISSUE_DO_NOTHING : MQ_ISSUE_INSERT_QUEUE;
break;
default:
dec = bypass ? MQ_ISSUE_DO_NOTHING : MQ_ISSUE_END_REQUEST;
@@ -1799,7 +1803,7 @@ static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
bool bypass)
{
struct request_queue *q = rq->q;
- bool run_queue = true;
+ bool run_queue = true, force = false;
blk_status_t ret = BLK_STS_RESOURCE;
enum mq_issue_decision dec;
int srcu_idx;
@@ -1814,7 +1818,7 @@ static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
*/
if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
run_queue = false;
- bypass = false;
+ force = true;
goto out_unlock;
}

@@ -1837,11 +1841,14 @@ static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
out_unlock:
hctx_unlock(hctx, srcu_idx);

- dec = blk_mq_make_dicision(ret, bypass);
+ dec = blk_mq_make_dicision(ret, bypass, force);
switch(dec) {
case MQ_ISSUE_INSERT_QUEUE:
blk_mq_sched_insert_request(rq, false, run_queue, false);
break;
+ case MQ_ISSUE_INSERT_DISPATCH:
+ blk_mq_request_bypass_insert(rq, run_queue);
+ break;
case MQ_ISSUE_END_REQUEST:
blk_mq_end_request(rq, ret);
break;
--
2.7.4
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