blob: eddd1e5921a51e433cfd01bb4904e61b7b12de31 [file] [log] [blame]
From da0b59fc5852270fd0f3f94ba3da27afe603ff4b Mon Sep 17 00:00:00 2001
From: Paolo Valente <>
Date: Mon, 3 Feb 2020 11:40:55 +0100
Subject: [PATCH] block, bfq: do not insert oom queue into position tree
commit 32c59e3a9a5a0b180dd015755d6d18ca31e55935 upstream.
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 <>
Tested-by: Oleksandr Natalenko <>
Signed-off-by: Paolo Valente <>
Signed-off-by: Jens Axboe <>
Signed-off-by: Paul Gortmaker <>
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index ed3b97dbcf63..40734cf8befe 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -613,6 +613,10 @@ 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