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| author |   Paolo Valente <paolo.valente@linaro.org> | 2019-06-25 07:12:44 +0200 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2019-06-25 09:07:34 -0600 |
| commit | db599f9ed9bd31b018b6c48ad7c6b21d5b790ecf (patch) | |
| tree | bc003791219b878b55104a71530e0f59a4af264c /block | |
| parent | block, bfq: reset inject limit when think-time state changes (diff) | |
| download | linux-dev-db599f9ed9bd31b018b6c48ad7c6b21d5b790ecf.tar.xz linux-dev-db599f9ed9bd31b018b6c48ad7c6b21d5b790ecf.zip | |
block, bfq: fix rq_in_driver check in bfq_update_inject_limit
One of the cases where the parameters for injection may be updated is
when there are no more in-flight I/O requests. The number of in-flight
requests is stored in the field bfqd->rq_in_driver of the descriptor
bfqd of the device. So, the controlled condition is
bfqd->rq_in_driver == 0.
Unfortunately, this is wrong because, the instruction that checks this
condition is in the code path that handles the completion of a
request, and, in particular, the instruction is executed before
bfqd->rq_in_driver is decremented in such a code path.
This commit fixes this issue by just replacing 0 with 1 in the
comparison.
Reported-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>
Tested-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/bfq-iosched.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 9bc10198ddff..05041f84b8da 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -5481,8 +5481,14 @@ static void bfq_update_inject_limit(struct bfq_data *bfqd, * total service time, and there seem to be the right * conditions to do it, or we can lower the last base value * computed. + * + * NOTE: (bfqd->rq_in_driver == 1) means that there is no I/O + * request in flight, because this function is in the code + * path that handles the completion of a request of bfqq, and, + * in particular, this function is executed before + * bfqd->rq_in_driver is decremented in such a code path. */ - if ((bfqq->last_serv_time_ns == 0 && bfqd->rq_in_driver == 0) || + if ((bfqq->last_serv_time_ns == 0 && bfqd->rq_in_driver == 1) || tot_time_ns < bfqq->last_serv_time_ns) { bfqq->last_serv_time_ns = tot_time_ns; /* |