On Fri, 10 Jul 2015 10:12:11 +0900 Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx> wrote:
> Shrinker API does not handle nicely unregister_shrinker() on a not-registered
> ->shrinker. Looking at shrinker users, they all have to (a) carry on some sort
> of a flag telling that "unregister_shrinker()" will not blow up... or (b) just
> be fishy
>
> ...
>
> I was thinking of a trivial INIT_SHRINKER macro to init `struct shrinker'
> internal members (composed in email client, not tested)
>
> include/linux/shrinker.h
>
> #define INIT_SHRINKER(s) \
> do { \
> (s)->nr_deferred = NULL; \
> INIT_LIST_HEAD(&(s)->list); \
> } while (0)
Spose so. Although it would be simpler to change unregister_shrinker()
to bale out if list.next==NULL and then say "all zeroes is the
initialized state".
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -63,6 +63,12 @@ struct shrinker {
> };
> #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
>
> +#define INIT_SHRINKER(s) \
> + do { \
> + INIT_LIST_HEAD(&(s)->list); \
> + (s)->nr_deferred = NULL; \
> + } while (0)
> +
The only reason to make this a macro would be so that it can be used at
compile-time, with something like
static struct shrinker my_shrinker = INIT_SHRINKER(&my_shrinker);
But as we're not planning on doing that, we implement it in C, please.
Also, shrinker_init() would be a better name. Although we already
mucked up shrinker_register() and shrinker_unregister().
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