Re: [PATCH v2] bcachefs: chardev: make bch_chardev_class constant

[Hongbo Li]

On 2024/3/11 9:41, Hongbo Li wrote:
> It's fine for me.
>
> On 2024/3/8 20:12, Ricardo B. Marliere wrote:
> > Since commit 43a7206b0963 ("driver core: class: make class_register() 
> > take
> > a const *"), the driver core allows for struct class to be in read-only
> > memory, so move the bch_chardev_class structure to be declared at build
> > time placing it into read-only memory, instead of having to be 
> > dynamically
> > allocated at boot time. Also, correctly clean up after failing paths in
> > bch2_chardev_init().
> >
> > Cc: Hongbo Li <lihongbo22@xxxxxxxxxx>
> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Suggested-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Ricardo B. Marliere <ricardo@xxxxxxxxxxxx>
> > ---
> > Changes in v2:
> > - Used "free the last thing" pattern in bch2_chardev_init().
> > - Link to v1: 
> > https://lore.kernel.org/r/20240305-bcachefs-v1-1-436196e25729@xxxxxxxxxxxx
> > ---
> >   fs/bcachefs/chardev.c | 35 ++++++++++++++++++++++-------------
> >   1 file changed, 22 insertions(+), 13 deletions(-)
> >
> > diff --git a/fs/bcachefs/chardev.c b/fs/bcachefs/chardev.c
> > index 226b39c17667..dc09f547dae6 100644
> > --- a/fs/bcachefs/chardev.c
> > +++ b/fs/bcachefs/chardev.c
> > @@ -940,7 +940,9 @@ static const struct file_operations 
> > bch_chardev_fops = {
> >   };
> >   static int bch_chardev_major;
> > -static struct class *bch_chardev_class;
> > +static const struct class bch_chardev_class = {
> > +    .name = "bcachefs",
> > +};
> >   static struct device *bch_chardev;
> >   void bch2_fs_chardev_exit(struct bch_fs *c)
> > @@ -957,7 +959,7 @@ int bch2_fs_chardev_init(struct bch_fs *c)
> >       if (c->minor < 0)
> >           return c->minor;
> > -    c->chardev = device_create(bch_chardev_class, NULL,
> > +    c->chardev = device_create(&bch_chardev_class, NULL,
> >                      MKDEV(bch_chardev_major, c->minor), c,
> >                      "bcachefs%u-ctl", c->minor);
> >       if (IS_ERR(c->chardev))
> > @@ -968,32 +970,39 @@ int bch2_fs_chardev_init(struct bch_fs *c)
> >   void bch2_chardev_exit(void)
> >   {
> > -    if (!IS_ERR_OR_NULL(bch_chardev_class))
> > -        device_destroy(bch_chardev_class,
> > -                   MKDEV(bch_chardev_major, U8_MAX));
> > -    if (!IS_ERR_OR_NULL(bch_chardev_class))
> > -        class_destroy(bch_chardev_class);
> > +    device_destroy(&bch_chardev_class, MKDEV(bch_chardev_major, 
> > U8_MAX));
> > +    class_unregister(&bch_chardev_class);
> >       if (bch_chardev_major > 0)
> >           unregister_chrdev(bch_chardev_major, "bcachefs");
> >   }
> >   int __init bch2_chardev_init(void)
> >   {
> > +    int ret;
> > +
> >       bch_chardev_major = register_chrdev(0, "bcachefs-ctl", 
> > &bch_chardev_fops);
> >       if (bch_chardev_major < 0)
> >           return bch_chardev_major;
> > -    bch_chardev_class = class_create("bcachefs");
> > -    if (IS_ERR(bch_chardev_class))
> > -        return PTR_ERR(bch_chardev_class);
> > +    ret = class_register(&bch_chardev_class);
> > +    if (ret)
> > +        goto major_out;
> > -    bch_chardev = device_create(bch_chardev_class, NULL,
> > +    bch_chardev = device_create(&bch_chardev_class, NULL,
> >                       MKDEV(bch_chardev_major, U8_MAX),
> >                       NULL, "bcachefs-ctl");
> > -    if (IS_ERR(bch_chardev))
> > -        return PTR_ERR(bch_chardev);
> > +    if (IS_ERR(bch_chardev)) {
> > +        ret = PTR_ERR(bch_chardev);
> > +        goto class_out;
> > +    }
> >       return 0;
> > +
> > +class_out:
> > +    class_unregister(&bch_chardev_class);
> > +major_out:
> > +    unregister_chrdev(bch_chardev_major, "bcachefs-ctl");
> > +    return ret;
> >   }
> >   #endif /* NO_BCACHEFS_CHARDEV */
> >
> > ---
> > base-commit: 90d35da658da8cff0d4ecbb5113f5fac9d00eb72
> > change-id: 20240305-bcachefs-27a4bb8b9f4f
> >
> > Best regards,

This is a useful patch, and also works on latest code. Maybe we almost 
forgot it.

Reviewed-by: Hongbo Li <lihongbo22@xxxxxxxxxx>