在 12/07/2019 10:47, Ming Lei 写道:
We will stop hw queue and wait for completion of in-flight requests
when one hctx is becoming dead in the following patch. This way may
cause dead-lock for some stacking blk-mq drivers, such as dm-rq and
loop.
Add blk-mq flag of BLK_MQ_F_NO_MANAGED_IRQ and mark it for dm-rq and
loop, so we needn't to wait for completion of in-flight requests of
dm-rq & loop, then the potential dead-lock can be avoided.
Wouldn't it make more sense to have the flag name be like
BLK_MQ_F_DONT_DRAIN_STOPPED_HCTX?
I did not think that blk-mq is specifically concerned with managed
interrupts, but only their indirect effect.
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-mq-debugfs.c | 1 +
drivers/block/loop.c | 2 +-
drivers/md/dm-rq.c | 2 +-
include/linux/blk-mq.h | 1 +
4 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index af40a02c46ee..24fff8c90942 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -240,6 +240,7 @@ static const char *const hctx_flag_name[] = {
HCTX_FLAG_NAME(TAG_SHARED),
HCTX_FLAG_NAME(BLOCKING),
HCTX_FLAG_NAME(NO_SCHED),
+ HCTX_FLAG_NAME(NO_MANAGED_IRQ),
};
#undef HCTX_FLAG_NAME
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 44c9985f352a..199d76e8bf46 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1986,7 +1986,7 @@ static int loop_add(struct loop_device **l, int i)
lo->tag_set.queue_depth = 128;
lo->tag_set.numa_node = NUMA_NO_NODE;
lo->tag_set.cmd_size = sizeof(struct loop_cmd);
- lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+ lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_NO_MANAGED_IRQ;
nit: at this point in the series you're setting a flag which is never
checked.
lo->tag_set.driver_data = lo;
err = blk_mq_alloc_tag_set(&lo->tag_set);
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 5f7063f05ae0..f7fbef2d3cd7 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -546,7 +546,7 @@ int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t)
md->tag_set->ops = &dm_mq_ops;
md->tag_set->queue_depth = dm_get_blk_mq_queue_depth();
md->tag_set->numa_node = md->numa_node_id;
- md->tag_set->flags = BLK_MQ_F_SHOULD_MERGE;
+ md->tag_set->flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_NO_MANAGED_IRQ;
md->tag_set->nr_hw_queues = dm_get_blk_mq_nr_hw_queues();
md->tag_set->driver_data = md;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 3a731c3c0762..911cdc6479dc 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -219,6 +219,7 @@ struct blk_mq_ops {
enum {
BLK_MQ_F_SHOULD_MERGE = 1 << 0,
BLK_MQ_F_TAG_SHARED = 1 << 1,
+ BLK_MQ_F_NO_MANAGED_IRQ = 1 << 2,
BLK_MQ_F_BLOCKING = 1 << 5,
BLK_MQ_F_NO_SCHED = 1 << 6,
BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,
