Commit 32c59e3a authored by Paolo Valente's avatar Paolo Valente Committed by Jens Axboe

block, bfq: do not insert oom queue into position tree

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: default avatarPatrick Dung <patdung100@gmail.com>
Tested-by: default avatarOleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f718b093
...@@ -613,6 +613,10 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq) ...@@ -613,6 +613,10 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
bfqq->pos_root = NULL; 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 * bfqq cannot be merged any longer (see comments in
* bfq_setup_cooperator): no point in adding bfqq into the * bfq_setup_cooperator): no point in adding bfqq into the
......
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