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Subject: Re: [PATCH] bcache: make kobj_type structures constant
From:   Coly Li <colyli@suse.de>
In-Reply-To: <20230214-kobj_type-bcache-v1-1-cf00ead7bee7@weissschuh.net>
Date:   Tue, 14 Feb 2023 17:51:09 +0800
Cc:     Kent Overstreet <kent.overstreet@gmail.com>,
        linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Transfer-Encoding: quoted-printable
Message-Id: <125CA8D6-D3B7-42FB-83BE-DCA688F2ACAF@suse.de>
References: <20230214-kobj_type-bcache-v1-1-cf00ead7bee7@weissschuh.net>
To:     =?utf-8?Q?Thomas_Wei=C3=9Fschuh?= <linux@weissschuh.net>
Precedence: bulk


> 2023=E5=B9=B42=E6=9C=8814=E6=97=A5 11:13=EF=BC=8CThomas Wei=C3=9Fschuh =
<linux@weissschuh.net> =E5=86=99=E9=81=93=EF=BC=9A
>=20
> Since commit ee6d3dd4ed48 ("driver core: make kobj_type constant.")
> the driver core allows the usage of const struct kobj_type.
>=20
> Take advantage of this to constify the structure definitions to =
prevent
> modification at runtime.
>=20

How the const structure definition can prevent modification at run time?

Thanks.

Coly Li


> Signed-off-by: Thomas Wei=C3=9Fschuh <linux@weissschuh.net>
> ---
> drivers/md/bcache/bcache.h | 10 +++++-----
> drivers/md/bcache/sysfs.h  |  2 +-
> 2 files changed, 6 insertions(+), 6 deletions(-)
>=20
> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
> index aebb7ef10e63..a522f4f1f992 100644
> --- a/drivers/md/bcache/bcache.h
> +++ b/drivers/md/bcache/bcache.h
> @@ -1004,11 +1004,11 @@ extern struct workqueue_struct *bch_flush_wq;
> extern struct mutex bch_register_lock;
> extern struct list_head bch_cache_sets;
>=20
> -extern struct kobj_type bch_cached_dev_ktype;
> -extern struct kobj_type bch_flash_dev_ktype;
> -extern struct kobj_type bch_cache_set_ktype;
> -extern struct kobj_type bch_cache_set_internal_ktype;
> -extern struct kobj_type bch_cache_ktype;
> +extern const struct kobj_type bch_cached_dev_ktype;
> +extern const struct kobj_type bch_flash_dev_ktype;
> +extern const struct kobj_type bch_cache_set_ktype;
> +extern const struct kobj_type bch_cache_set_internal_ktype;
> +extern const struct kobj_type bch_cache_ktype;
>=20
> void bch_cached_dev_release(struct kobject *kobj);
> void bch_flash_dev_release(struct kobject *kobj);
> diff --git a/drivers/md/bcache/sysfs.h b/drivers/md/bcache/sysfs.h
> index a2ff6447b699..65b8bd975ab1 100644
> --- a/drivers/md/bcache/sysfs.h
> +++ b/drivers/md/bcache/sysfs.h
> @@ -3,7 +3,7 @@
> #define _BCACHE_SYSFS_H_
>=20
> #define KTYPE(type) \
> -struct kobj_type type ## _ktype =3D { \
> +const struct kobj_type type ## _ktype =3D { \
> .release =3D type ## _release, \
> .sysfs_ops =3D &((const struct sysfs_ops) { \
> .show =3D type ## _show, \
>=20
> ---
> base-commit: f6feea56f66d34259c4222fa02e8171c4f2673d1
> change-id: 20230214-kobj_type-bcache-6d2bd129b0fa
>=20
> Best regards,
> --=20
> Thomas Wei=C3=9Fschuh <linux@weissschuh.net>
>=20