From: Hongbo Li <lihongbo22@huawei.com>
To: "Ricardo B. Marliere" <ricardo@marliere.net>
Cc: Kent Overstreet <kent.overstreet@linux.dev>,
Brian Foster <bfoster@redhat.com>,
<linux-bcachefs@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] bcachefs: chardev: make bch_chardev_class constant
Date: Wed, 6 Mar 2024 21:01:59 +0800 [thread overview]
Message-ID: <df64802a-02fd-4f72-b9ec-7812e2779df3@huawei.com> (raw)
In-Reply-To: <sky4no6qxoytrkd3azcf5hokmhxrrpluao5ilhbqvprqxwuj4r@ozwmbbulfbrt>
On 2024/3/6 19:50, Ricardo B. Marliere wrote:
> On 6 Mar 09:23, Hongbo Li wrote:
>> On 2024/3/6 4:21, 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.
>>>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
>>> ---
>>> fs/bcachefs/chardev.c | 23 ++++++++++++-----------
>>> 1 file changed, 12 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/fs/bcachefs/chardev.c b/fs/bcachefs/chardev.c
>>> index 226b39c17667..af587453fd3d 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))
>>> @@ -968,26 +970,25 @@ 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)
>> Here, I think you should call class_unregister to relase resource which
>> allocated before. And the same thing shoud be done in other exception exit.
>
> Hi Hongbo,
>
> Thank you for the feedback. Did you mean that bch_chardev_major should
> be unregistered if the class_register() call fails? Because if it does,
> there is no need to call class_unregister().
>
>>> + return ret;
>>>
>>> - 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))
>> like here..
>
> Can you please elaborate?
>
Yes, this I mean. The example like this:
```c
major = register_chrdev(0, xx, xx);
class = class_create("bcachefs");
if (IS_ERR(class))
goto out_chrdev:
...
out_class:
class_unregister(xxx);
out_chrdev:
unregister_chrdev(xx, xx);
...
```
Although this was not part of your original intention, it is indeed a flaw.
> Best regards,
> - Ricardo.
>
>
>>>
>>> ---
>>> base-commit: 90d35da658da8cff0d4ecbb5113f5fac9d00eb72
>>> change-id: 20240305-bcachefs-27a4bb8b9f4f
>>>
>>> Best regards,
>
next prev parent reply other threads:[~2024-03-06 13:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-05 20:21 [PATCH] bcachefs: chardev: make bch_chardev_class constant Ricardo B. Marliere
2024-03-06 1:23 ` Hongbo Li
2024-03-06 11:50 ` Ricardo B. Marliere
2024-03-06 13:01 ` Hongbo Li [this message]
2024-03-08 2:18 ` Kent Overstreet
2024-03-08 12:14 ` Ricardo B. Marliere
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