linux-ext4 - Re: [PATCH v3 03/15] fanotify: Split fsid check from other fid mode checks

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Date:   Wed, 7 Jul 2021 21:24:26 +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 03/15] fanotify: Split fsid check from other fid mode
 checks

On Tue 29-06-21 15:10:23, Gabriel Krisman Bertazi wrote:
> FAN_FS_ERROR will require fsid, but not necessarily require the
> filesystem to expose a file handle.  Split those checks into different
> functions, so they can be used separately when setting up an event.
> 
> While there, update a comment about tmpfs having 0 fsid, which is no
> longer true.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>

Looks good. Feel free to add:

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

								Honza

> 
> ---
> Changes since v2:
>   - FAN_ERROR -> FAN_FS_ERROR (Amir)
>   - Update comment (Amir)
> 
> Changes since v1:
>   (Amir)
>   - Sort hunks to simplify diff.
> Changes since RFC:
>   (Amir)
>   - Rename fanotify_check_path_fsid -> fanotify_test_fsid.
>   - Use dentry directly instead of path.
> ---
>  fs/notify/fanotify/fanotify_user.c | 27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 68a53d3534f8..67b18dfe0025 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -1192,16 +1192,15 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
>  	return fd;
>  }
>  
> -/* Check if filesystem can encode a unique fid */
> -static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
> +static int fanotify_test_fsid(struct dentry *dentry, __kernel_fsid_t *fsid)
>  {
>  	__kernel_fsid_t root_fsid;
>  	int err;
>  
>  	/*
> -	 * Make sure path is not in filesystem with zero fsid (e.g. tmpfs).
> +	 * Make sure dentry is not of a filesystem with zero fsid (e.g. fuse).
>  	 */
> -	err = vfs_get_fsid(path->dentry, fsid);
> +	err = vfs_get_fsid(dentry, fsid);
>  	if (err)
>  		return err;
>  
> @@ -1209,10 +1208,10 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
>  		return -ENODEV;
>  
>  	/*
> -	 * Make sure path is not inside a filesystem subvolume (e.g. btrfs)
> +	 * Make sure dentry is not of a filesystem subvolume (e.g. btrfs)
>  	 * which uses a different fsid than sb root.
>  	 */
> -	err = vfs_get_fsid(path->dentry->d_sb->s_root, &root_fsid);
> +	err = vfs_get_fsid(dentry->d_sb->s_root, &root_fsid);
>  	if (err)
>  		return err;
>  
> @@ -1220,6 +1219,12 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
>  	    root_fsid.val[1] != fsid->val[1])
>  		return -EXDEV;
>  
> +	return 0;
> +}
> +
> +/* Check if filesystem can encode a unique fid */
> +static int fanotify_test_fid(struct dentry *dentry)
> +{
>  	/*
>  	 * We need to make sure that the file system supports at least
>  	 * encoding a file handle so user can use name_to_handle_at() to
> @@ -1227,8 +1232,8 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
>  	 * objects. However, name_to_handle_at() requires that the
>  	 * filesystem also supports decoding file handles.
>  	 */
> -	if (!path->dentry->d_sb->s_export_op ||
> -	    !path->dentry->d_sb->s_export_op->fh_to_dentry)
> +	if (!dentry->d_sb->s_export_op ||
> +	    !dentry->d_sb->s_export_op->fh_to_dentry)
>  		return -EOPNOTSUPP;
>  
>  	return 0;
> @@ -1379,7 +1384,11 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
>  	}
>  
>  	if (fid_mode) {
> -		ret = fanotify_test_fid(&path, &__fsid);
> +		ret = fanotify_test_fsid(path.dentry, &__fsid);
> +		if (ret)
> +			goto path_put_and_out;
> +
> +		ret = fanotify_test_fid(path.dentry);
>  		if (ret)
>  			goto path_put_and_out;
>  
> -- 
> 2.32.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR