blk-mq: fix "bad unlock balance detected" on q->srcu in __blk_mq_run_dispatch_ops

The 'q' parameter of the macro __blk_mq_run_dispatch_ops may not be one
local variable, such as, it is rq->q, then request queue pointed by
this variable could be changed to another queue in case of
BLK_MQ_F_TAG_QUEUE_SHARED after 'dispatch_ops' returns, then
'bad unlock balance' is triggered.

Fixes the issue by adding one local variable for doing srcu lock/unlock.

Fixes: 2a904d00855f ("blk-mq: remove hctx_lock and hctx_unlock")
Cc: Marco Patalano <mpatalan@redhat.com>
Signed-off-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230310010913.1014789-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.h b/block/blk-mq.h
index ef59fee..a7482d2 100644 (file)
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -378,12 +378,13 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
 #define __blk_mq_run_dispatch_ops(q, check_sleep, dispatch_ops)        \
 do {                                                           \
        if ((q)->tag_set->flags & BLK_MQ_F_BLOCKING) {          \
+               struct blk_mq_tag_set *__tag_set = (q)->tag_set; \
                int srcu_idx;                                   \
                                                                \
                might_sleep_if(check_sleep);                    \
-               srcu_idx = srcu_read_lock((q)->tag_set->srcu);  \
+               srcu_idx = srcu_read_lock(__tag_set->srcu);     \
                (dispatch_ops);                                 \
-               srcu_read_unlock((q)->tag_set->srcu, srcu_idx); \
+               srcu_read_unlock(__tag_set->srcu, srcu_idx);    \
        } else {                                                \
                rcu_read_lock();                                \
                (dispatch_ops);                                 \