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blk-wbt: fix IO hang in wbt_wait() 

On wbt invariant is that if one IO is tracked via WBT_TRACKED, rqw->inflight
should be updated for tracking this IO.

But commit c1c80384c8 ("block: remove external dependency on wbt_flags")
forgets to remove the early handling of !rwb_enabled(rwb) inside wbt_wait(),
then the inflight counter may not be increased in wbt_wait(), but decreased
in wbt_done() for this kind of IO, so this counter may become negative, then
wbt_wait() may wait forever.

This patch fixes the report in the following link:

	https://marc.info/?l=linux-block&m=153221542021033&w=2

Fixes: c1c80384c8 ("block: remove external dependency on wbt_flags")
Cc: Josef Bacik <jbacik@fb.com>
Reported-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2018-08-14 23:57:49 +08:00 committed by Jens Axboe
parent b089cfd95d
commit df60f6e835
1 changed files with 1 additions and 5 deletions
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6
block/blk-wbt.c
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@ -576,12 +576,8 @@ static void wbt_wait(struct rq_qos *rqos, struct bio *bio, spinlock_t *lock)
struct rq_wb *rwb = RQWB(rqos);
enum wbt_flags flags;
if (!rwb_enabled(rwb))
return;
flags = bio_to_wbt_flags(rwb, bio);
if (!wbt_should_throttle(rwb, bio)) {
if (!(flags & WBT_TRACKED)) {
if (flags & WBT_READ)
wb_timestamp(rwb, &rwb->last_issue);
return;