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| author | Paolo Valente <paolo.valente@linaro.org> | 2021-12-21 14:38:48 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-12-29 14:20:42 +0300 |
| commit | 99ada24490c3464b372e534fcdf3d641e912327d (patch) | |
| tree | d492b1cd86c87e34c649b4bbebdefbd603ce3a1f /block/bfq-iosched.c | |
| parent | 7d0efcc69c75adb98fce47c7ddd4135b99a71392 (diff) | |
| download | linux-99ada24490c3464b372e534fcdf3d641e912327d.tar.xz | |
block, bfq: fix queue removal from weights tree
commit 9dee8b3b057e1da26f85f1842f2aaf3bb200fb94 upstream.
bfq maintains an ordered list, through a red-black tree, of unique
weights of active bfq_queues. This list is used to detect whether there
are active queues with differentiated weights. The weight of a queue is
removed from the list when both the following two conditions become
true:
(1) the bfq_queue is flagged as inactive
(2) the has no in-flight request any longer;
Unfortunately, in the rare cases where condition (2) becomes true before
condition (1), the removal fails, because the function to remove the
weight of the queue (bfq_weights_tree_remove) is rightly invoked in the
path that deactivates the bfq_queue, but mistakenly invoked *before* the
function that actually performs the deactivation (bfq_deactivate_bfqq).
This commits moves the invocation of bfq_weights_tree_remove for
condition (1) to after bfq_deactivate_bfqq. As a consequence of this
move, it is necessary to add a further reference to the queue when the
weight of a queue is added, because the queue might otherwise be freed
before bfq_weights_tree_remove is invoked. This commit adds this
reference and makes all related modifications.
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'block/bfq-iosched.c')
| -rw-r--r-- | block/bfq-iosched.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index d5daf6e05771..d22452fa2d5a 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -748,6 +748,7 @@ void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq, inc_counter: bfqq->weight_counter->num_active++; + bfqq->ref++; } /* @@ -772,6 +773,7 @@ void __bfq_weights_tree_remove(struct bfq_data *bfqd, reset_entity_pointer: bfqq->weight_counter = NULL; + bfq_put_queue(bfqq); } /* @@ -783,9 +785,6 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd, { struct bfq_entity *entity = bfqq->entity.parent; - __bfq_weights_tree_remove(bfqd, bfqq, - &bfqd->queue_weights_tree); - for_each_entity(entity) { struct bfq_sched_data *sd = entity->my_sched_data; @@ -819,6 +818,15 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd, bfqd->num_groups_with_pending_reqs--; } } + + /* + * Next function is invoked last, because it causes bfqq to be + * freed if the following holds: bfqq is not in service and + * has no dispatched request. DO NOT use bfqq after the next + * function invocation. + */ + __bfq_weights_tree_remove(bfqd, bfqq, + &bfqd->queue_weights_tree); } /* @@ -1012,7 +1020,8 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd, static int bfqq_process_refs(struct bfq_queue *bfqq) { - return bfqq->ref - bfqq->allocated - bfqq->entity.on_st; + return bfqq->ref - bfqq->allocated - bfqq->entity.on_st - + (bfqq->weight_counter != NULL); } /* Empty burst list and add just bfqq (see comments on bfq_handle_burst) */ |