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SubjectRe: [PATCH 15/20] io-controller: map async requests to appropriate cgroup
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Hi Vivek,

> +#ifdef CONFIG_TRACK_ASYNC_CONTEXT
> + if (elv_bio_sync(bio)) {
> + /* sync io. Determine cgroup from submitting task context. */
> + cgroup = task_cgroup(current, io_subsys_id);
> + return cgroup;
> + }
> +
> + /* Async io. Determine cgroup from with cgroup id stored in page */
> + bio_cgroup_id = get_blkio_cgroup_id(bio);
> +
> + if (!bio_cgroup_id)
> + return NULL;
> +
> + cgroup = blkio_cgroup_lookup(bio_cgroup_id);
> +#else
> + cgroup = task_cgroup(current, io_subsys_id);
> +#endif
> + return cgroup;
> +}

There is a case where a kernel thread (such as device-mapper drivers)
submits a sync IO instead of a task which originates the IO. I think
you should always use get_blkio_cgroup_id() to determine cgroup.

Thanks,
Ryo Tsuruta


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