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SubjectRe: [PATCH] block: put the reference of the io scheduler module after switching back
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Hi!

在 2022/10/11 18:21, Jinlong Chen 写道:
> We got a reference of the io scheduler module in
> blk_mq_elv_switch_none to prevent the module from
> being removed. We need to put that reference back
> once we are done.

However, if blk_mq_elv_switch_none() failed due to OOM, and module
reference is not acquired, blk_mq_elv_switch_back() will still be
called. This seems not to be the right fix.

Thanks,
Kuai
>
> Signed-off-by: Jinlong Chen <chenjinlong2016@outlook.com>
> ---
> block/blk-mq.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 8070b6c10e8d..8dfe3bf3e599 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -4595,6 +4595,13 @@ static void blk_mq_elv_switch_back(struct list_head *head,
>
> mutex_lock(&q->sysfs_lock);
> elevator_switch(q, t);
> + /**
> + * We got a reference of the io scheduler module in
> + * blk_mq_elv_switch_none to prevent the module from
> + * being removed. We need to put that reference back
> + * once we are done.
> + */
> + module_put(t->elevator_owner);
> mutex_unlock(&q->sysfs_lock);
> }
>
>

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