| From 26c2b0426f2bbb2d2c49e274be96aa901c9ce5e4 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 3 Feb 2020 11:40:55 +0100 |
| Subject: block, bfq: do not insert oom queue into position tree |
| |
| From: Paolo Valente <paolo.valente@linaro.org> |
| |
| [ 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@gmail.com> |
| Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> |
| Signed-off-by: Paolo Valente <paolo.valente@linaro.org> |
| Signed-off-by: Jens Axboe <axboe@kernel.dk> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| 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 |
| |
