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authorJens Axboe <axboe@kernel.dk>2017-11-09 18:32:43 +0300
committerJens Axboe <axboe@kernel.dk>2017-11-11 05:53:25 +0300
commiteb619fdb2d4cb8b3d3419e9113921e87e7daf557 (patch)
tree491c0230e3ce0cead62bf59b090bf6c8b2bbd6e0 /include/linux/blk-mq.h
parente454d122e22826589cfa08788a802ab09d4fae24 (diff)
downloadlinux-eb619fdb2d4cb8b3d3419e9113921e87e7daf557.tar.xz
blk-mq: fix issue with shared tag queue re-running
This patch attempts to make the case of hctx re-running on driver tag failure more robust. Without this patch, it's pretty easy to trigger a stall condition with shared tags. An example is using null_blk like this: modprobe null_blk queue_mode=2 nr_devices=4 shared_tags=1 submit_queues=1 hw_queue_depth=1 which sets up 4 devices, sharing the same tag set with a depth of 1. Running a fio job ala: [global] bs=4k rw=randread norandommap direct=1 ioengine=libaio iodepth=4 [nullb0] filename=/dev/nullb0 [nullb1] filename=/dev/nullb1 [nullb2] filename=/dev/nullb2 [nullb3] filename=/dev/nullb3 will inevitably end with one or more threads being stuck waiting for a scheduler tag. That IO is then stuck forever, until someone else triggers a run of the queue. Ensure that we always re-run the hardware queue, if the driver tag we were waiting for got freed before we added our leftover request entries back on the dispatch list. Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com> Tested-by: Bart Van Assche <bart.vanassche@wdc.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux/blk-mq.h')
-rw-r--r--include/linux/blk-mq.h5
1 files changed, 2 insertions, 3 deletions
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 674641527da7..4ae987c2352c 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -35,7 +35,7 @@ struct blk_mq_hw_ctx {
struct blk_mq_ctx **ctxs;
unsigned int nr_ctx;
- wait_queue_entry_t dispatch_wait;
+ wait_queue_entry_t dispatch_wait;
atomic_t wait_index;
struct blk_mq_tags *tags;
@@ -181,8 +181,7 @@ enum {
BLK_MQ_S_STOPPED = 0,
BLK_MQ_S_TAG_ACTIVE = 1,
BLK_MQ_S_SCHED_RESTART = 2,
- BLK_MQ_S_TAG_WAITING = 3,
- BLK_MQ_S_START_ON_RUN = 4,
+ BLK_MQ_S_START_ON_RUN = 3,
BLK_MQ_MAX_DEPTH = 10240,