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References: <YcKDAILGEoYFE7K0@B-P7TQMD6M-0146.local>
 <20211222014917.265476-1-zhangkelvin@google.com>
In-Reply-To: <20211222014917.265476-1-zhangkelvin@google.com>
Date: Tue, 4 Jan 2022 15:37:51 -0800
Message-ID: <CAOSmRzgOB-78BSc4Ug-xNnS+Cc6x8AZ8zEVTYPU4iiKcOowVWQ@mail.gmail.com>
Subject: Re: [PATCH v2 1/3] erofs-utils: lib: Add some comments about
 const-ness around iterate API
To: linux-erofs mailing list <linux-erofs@lists.ozlabs.org>,
 Miao Xie <miaoxie@huawei.com>, Fang Wei <fangwei1@huawei.com>
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From: Kelvin Zhang via Linux-erofs <linux-erofs@lists.ozlabs.org>
Reply-To: Kelvin Zhang <zhangkelvin@google.com>
Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org
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 <linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org>

friendly ping

On Tue, Dec 21, 2021 at 5:49 PM Kelvin Zhang <zhangkelvin@google.com> wrote:
>
> The new iterate dir API has non-trivial const correctness requirements.
> Document them in comment.
>
> Signed-off-by: Kelvin Zhang <zhangkelvin@google.com>
> ---
>  include/erofs/dir.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/include/erofs/dir.h b/include/erofs/dir.h
> index 77656ca..59bd40d 100644
> --- a/include/erofs/dir.h
> +++ b/include/erofs/dir.h
> @@ -39,6 +39,14 @@ typedef int (*erofs_readdir_cb)(struct erofs_dir_context *);
>   * the callback context. |de_namelen| is the exact dirent name length.
>   */
>  struct erofs_dir_context {
> +       /* During execution of |erofs_iterate_dir|, the function needs
> +        * to read the values inside |erofs_inode* dir|. So it is important
> +        * that the callback function does not modify stuct pointed by
> +        * |dir|. It is OK to repoint |dir| to other objects.
> +        * Unfortunately, it's not possible to enforce this restriction
> +        * with const keyword, as |erofs_iterate_dir| needs to modify
> +        * struct pointed by |dir|.
> +        */
>         struct erofs_inode *dir;
>         erofs_readdir_cb cb;
>         erofs_nid_t pnid;               /* optional */
> --
> 2.34.1.448.ga2b2bfdf31-goog
>


-- 
Sincerely,

Kelvin Zhang