From: Paolo Valente <paolo.valente@xxxxxxxxxx> [ Upstream commit 32c59e3a9a5a0b180dd015755d6d18ca31e55935 ] BFQ maintains an ordered list, implemented with an RB tree, of head-request positions of non-empty bfq_queues. This position tree, inherited from CFQ, is used to find bfq_queues that contain I/O close to each other. BFQ merges these bfq_queues into a single shared queue, if this boosts throughput on the device at hand. There is however a special-purpose bfq_queue that does not participate in queue merging, the oom bfq_queue. Yet, also this bfq_queue could be wrongly added to the position tree. So bfqq_find_close() could return the oom bfq_queue, which is a source of further troubles in an out-of-memory situation. This commit prevents the oom bfq_queue from being inserted into the position tree. Tested-by: Patrick Dung <patdung100@xxxxxxxxx> Tested-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx> Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- block/bfq-iosched.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 5c239c540c47a..3dbd0666fec1b 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -614,6 +614,10 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq) bfqq->pos_root = NULL; } + /* oom_bfqq does not participate in queue merging */ + if (bfqq == &bfqd->oom_bfqq) + return; + /* * bfqq cannot be merged any longer (see comments in * bfq_setup_cooperator): no point in adding bfqq into the -- 2.20.1
