On Thu 26-01-17 12:41:30, Dan Williams wrote:
> 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.
The free_on_put is there for static incarnations of this structure...
However yes, I can have a look into grabbing the reference on module init
for these cases so that we can avoid the flag.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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