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authorPaolo Valente <paolo.valente@linaro.org>2019-06-25 08:12:44 +0300
committerJens Axboe <axboe@kernel.dk>2019-06-25 18:07:34 +0300
commitdb599f9ed9bd31b018b6c48ad7c6b21d5b790ecf (patch)
treebc003791219b878b55104a71530e0f59a4af264c /block/bfq-iosched.c
parent766d61412ef840295f55e98e2c5fb0fc110c6ca4 (diff)
downloadlinux-db599f9ed9bd31b018b6c48ad7c6b21d5b790ecf.tar.xz
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/bfq-iosched.c')
-rw-r--r--block/bfq-iosched.c8
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;
/*