Re: [PATCH v7 10/28] fsnotify: Retrieve super block from the data field

From: Jan Kara <jack@suse.cz>
To: Gabriel Krisman Bertazi <krisman@collabora.com>
Cc: jack@suse.com, amir73il@gmail.com, djwong@kernel.org,
	tytso@mit.edu, dhowells@redhat.com, khazhy@google.com,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-api@vger.kernel.org, repnop@google.com,
	kernel@collabora.com, Jan Kara <jack@suse.cz>
Subject: Re: [PATCH v7 10/28] fsnotify: Retrieve super block from the data field
Date: Fri, 15 Oct 2021 11:26:12 +0200	[thread overview]
Message-ID: <20211015092612.GD23102@quack2.suse.cz> (raw)
In-Reply-To: <20211014213646.1139469-11-krisman@collabora.com>

On Thu 14-10-21 18:36:28, Gabriel Krisman Bertazi wrote:
> Some file system events (i.e. FS_ERROR) might not be associated with an
> inode or directory.  For these, we can retrieve the super block from the
> data field.  But, since the super_block is available in the data field
> on every event type, simplify the code to always retrieve it from there,
> through a new helper.
> 
> Suggested-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> 
> --
> Changes since v6:
>   - Always use data field for superblock retrieval
> Changes since v5:
>   - add fsnotify_data_sb handle to retrieve sb from the data field. (jan)
> ---
>  fs/notify/fsnotify.c             |  7 +++----
>  include/linux/fsnotify_backend.h | 15 +++++++++++++++
>  2 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 963e6ce75b96..fde3a1115a17 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -455,16 +455,16 @@ static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
>   *		@file_name is relative to
>   * @file_name:	optional file name associated with event
>   * @inode:	optional inode associated with event -
> - *		either @dir or @inode must be non-NULL.
> - *		if both are non-NULL event may be reported to both.
> + *		If @dir and @inode are both non-NULL, event may be
> + *		reported to both.
>   * @cookie:	inotify rename cookie
>   */
>  int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
>  	     const struct qstr *file_name, struct inode *inode, u32 cookie)
>  {
>  	const struct path *path = fsnotify_data_path(data, data_type);
> +	struct super_block *sb = fsnotify_data_sb(data, data_type);
>  	struct fsnotify_iter_info iter_info = {};
> -	struct super_block *sb;
>  	struct mount *mnt = NULL;
>  	struct inode *parent = NULL;
>  	int ret = 0;
> @@ -483,7 +483,6 @@ int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
>  		 */
>  		parent = dir;
>  	}
> -	sb = inode->i_sb;
>  
>  	/*
>  	 * Optimization: srcu_read_lock() has a memory barrier which can
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index b323d0c4b967..035438fe4a43 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -289,6 +289,21 @@ static inline const struct path *fsnotify_data_path(const void *data,
>  	}
>  }
>  
> +static inline struct super_block *fsnotify_data_sb(const void *data,
> +						   int data_type)
> +{
> +	switch (data_type) {
> +	case FSNOTIFY_EVENT_INODE:
> +		return ((struct inode *)data)->i_sb;
> +	case FSNOTIFY_EVENT_DENTRY:
> +		return ((struct dentry *)data)->d_sb;
> +	case FSNOTIFY_EVENT_PATH:
> +		return ((const struct path *)data)->dentry->d_sb;
> +	default:
> +		return NULL;
> +	}
> +}
> +
>  enum fsnotify_obj_type {
>  	FSNOTIFY_OBJ_TYPE_INODE,
>  	FSNOTIFY_OBJ_TYPE_PARENT,
> -- 
> 2.33.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR