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-rw-r--r--block/blk-core.c1
-rw-r--r--block/blk-mq.c20
2 files changed, 17 insertions, 4 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index a2005a485335..134fd34b681f 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -145,6 +145,7 @@ static const struct {
[BLK_STS_MEDIUM] = { -ENODATA, "critical medium" },
[BLK_STS_PROTECTION] = { -EILSEQ, "protection" },
[BLK_STS_RESOURCE] = { -ENOMEM, "kernel resource" },
+ [BLK_STS_DEV_RESOURCE] = { -EBUSY, "device resource" },
[BLK_STS_AGAIN] = { -EAGAIN, "nonblocking retry" },
/* device mapper special case, should not leak out: */
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 01f271d40825..df93102e2149 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1162,6 +1162,8 @@ static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx **hctx,
return true;
}
+#define BLK_MQ_RESOURCE_DELAY 3 /* ms units */
+
bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
bool got_budget)
{
@@ -1169,6 +1171,7 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
struct request *rq, *nxt;
bool no_tag = false;
int errors, queued;
+ blk_status_t ret = BLK_STS_OK;
if (list_empty(list))
return false;
@@ -1181,7 +1184,6 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
errors = queued = 0;
do {
struct blk_mq_queue_data bd;
- blk_status_t ret;
rq = list_first_entry(list, struct request, queuelist);
if (!blk_mq_get_driver_tag(rq, &hctx, false)) {
@@ -1226,7 +1228,7 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
}
ret = q->mq_ops->queue_rq(hctx, &bd);
- if (ret == BLK_STS_RESOURCE) {
+ if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
/*
* If an I/O scheduler has been configured and we got a
* driver tag for the next request already, free it
@@ -1257,6 +1259,8 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
* that is where we will continue on next queue run.
*/
if (!list_empty(list)) {
+ bool needs_restart;
+
spin_lock(&hctx->lock);
list_splice_init(list, &hctx->dispatch);
spin_unlock(&hctx->lock);
@@ -1280,10 +1284,17 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
* - Some but not all block drivers stop a queue before
* returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
* and dm-rq.
+ *
+ * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
+ * bit is set, run queue after a delay to avoid IO stalls
+ * that could otherwise occur if the queue is idle.
*/
- if (!blk_mq_sched_needs_restart(hctx) ||
+ needs_restart = blk_mq_sched_needs_restart(hctx);
+ if (!needs_restart ||
(no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
blk_mq_run_hw_queue(hctx, true);
+ else if (needs_restart && (ret == BLK_STS_RESOURCE))
+ blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
}
return (queued + errors) != 0;
@@ -1764,6 +1775,7 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
*cookie = new_cookie;
break;
case BLK_STS_RESOURCE:
+ case BLK_STS_DEV_RESOURCE:
__blk_mq_requeue_request(rq);
break;
default:
@@ -1826,7 +1838,7 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
hctx_lock(hctx, &srcu_idx);
ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false);
- if (ret == BLK_STS_RESOURCE)
+ if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
blk_mq_sched_insert_request(rq, false, true, false);
else if (ret != BLK_STS_OK)
blk_mq_end_request(rq, ret);