On Thu, Jan 26, 2017 at 9:45 AM, Jan Kara <jack@xxxxxxx> wrote:
> Instead of storing backing_dev_info inside struct request_queue,
> allocate it dynamically, reference count it, and free it when the last
> reference is dropped. Currently only request_queue holds the reference
> but in the following patch we add other users referencing
> backing_dev_info.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
[..]
> diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
> index e850e76acaaf..4282f21b1611 100644
> --- a/include/linux/backing-dev-defs.h
> +++ b/include/linux/backing-dev-defs.h
> @@ -144,7 +144,9 @@ struct backing_dev_info {
>
> char *name;
>
> - unsigned int capabilities; /* Device capabilities */
> + atomic_t refcnt; /* Reference counter for the structure */
> + unsigned int capabilities:31; /* Device capabilities */
> + unsigned int free_on_put:1; /* Structure will be freed on last bdi_put() */
> unsigned int min_ratio;
> unsigned int max_ratio, max_prop_frac;
>
Any reason to not just use struct kref for this? The "free on final
put" should be implicit. In other words, if there is a path that would
ever clear this flag, then it really should just be holding its own
reference.
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