linux-ext4 - Re: [PATCH v3 07/15] fsnotify: pass arguments of fsnotify() in struct fsnotify_event

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Message-ID: <20210708104307.GA1656@quack2.suse.cz>
Date:   Thu, 8 Jul 2021 12:43:07 +0200
From:   Jan Kara <jack@...e.cz>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     amir73il@...il.com, djwong@...nel.org, tytso@....edu,
        david@...morbit.com, jack@...e.com, dhowells@...hat.com,
        khazhy@...gle.com, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH v3 07/15] fsnotify: pass arguments of fsnotify() in
 struct fsnotify_event_info

On Tue 29-06-21 15:10:27, Gabriel Krisman Bertazi wrote:
> From: Amir Goldstein <amir73il@...il.com>
> 
> There are a lot of arguments to fsnotify() and the handle_event() method.
> Pass them in a const struct instead of on the argument list.
> 
> Apart from being more tidy, this helps with passing error reports to the
> backend.  __fsnotify_parent() argument list was intentionally left
> untouched, because its argument list is still short enough and because
> most of the event info arguments are initialized inside
> __fsnotify_parent().
> 
> Signed-off-by: Amir Goldstein <amir73il@...il.com>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
> ---
>  fs/notify/fanotify/fanotify.c    | 59 +++++++++++------------
>  fs/notify/fsnotify.c             | 83 +++++++++++++++++---------------
>  include/linux/fsnotify.h         | 15 ++++--
>  include/linux/fsnotify_backend.h | 73 +++++++++++++++++++++-------
>  4 files changed, 140 insertions(+), 90 deletions(-)

Besides the noop function issue Amir has already pointed out I have just a
few nits:

> @@ -229,7 +229,11 @@ int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
>  	}
>  
>  notify:
> -	ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0);
> +	ret = __fsnotify(mask, &(struct fsnotify_event_info) {
> +				.data = data, .data_type = data_type,
> +				.dir = p_inode, .name = file_name,
> +				.inode = inode,
> +				});

What's the advantage of using __fsnotify() here instead of fsnotify()? In
terms of readability the fewer places with these initializers the better
I'd say...

>  static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask,
> -				 const void *data, int data_type,
> -				 struct inode *dir, const struct qstr *name,
> -				 u32 cookie, struct fsnotify_iter_info *iter_info)
> +				 const struct fsnotify_event_info *event_info,
> +				 struct fsnotify_iter_info *iter_info)
>  {
>  	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
>  	struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info);
> +	struct fsnotify_event_info child_event_info = { };
>  	int ret;

No need to init child_event_info. It is fully rewritten if it gets used...

> diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
> index f8acddcf54fb..8c2c681b4495 100644
> --- a/include/linux/fsnotify.h
> +++ b/include/linux/fsnotify.h
> @@ -30,7 +30,10 @@ static inline void fsnotify_name(struct inode *dir, __u32 mask,
>  				 struct inode *child,
>  				 const struct qstr *name, u32 cookie)
>  {
> -	fsnotify(mask, child, FSNOTIFY_EVENT_INODE, dir, name, NULL, cookie);
> +	__fsnotify(mask, &(struct fsnotify_event_info) {
> +			.data = child, .data_type = FSNOTIFY_EVENT_INODE,
> +			.dir = dir, .name = name, .cookie = cookie,
> +			});
>  }

Hmm, maybe we could have a macro initializer like:

#define FSNOTIFY_EVENT_INFO(data, data_type, dir, name, inode, cookie)	\
	(struct fsnotify_event_info) {					\
		.data = (data), .data_type = (data_type), .dir = (dir), \
		.name = (name), .inode = (inode), .cookie = (cookie)}

Then we'd have:
	__fsnotify(mask, &FSNOTIFY_EVENT_INFO(child, FSNOTIFY_EVENT_INODE,
				dir, name, NULL, cookie));

Which looks a bit nicer to me. What do you think guys?

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR