Re: [PATCH RFC 17/20] ubifs: store cookie in private data

[Jan Kara <jack@suse.cz>]

On Fri 30-08-24 15:04:58, Christian Brauner wrote:
> Store the cookie to detect concurrent seeks on directories in
> file->private_data.
> 
> Signed-off-by: Christian Brauner <brauner@kernel.org>

Looks good to me. Feel free to add:

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

								Honza

> ---
>  fs/ubifs/dir.c | 65 ++++++++++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 47 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
> index c77ea57fe696..76bcafa92200 100644
> --- a/fs/ubifs/dir.c
> +++ b/fs/ubifs/dir.c
> @@ -555,6 +555,11 @@ static unsigned int vfs_dent_type(uint8_t type)
>  	return 0;
>  }
>  
> +struct ubifs_dir_data {
> +	struct ubifs_dent_node *dent;
> +	u64 cookie;
> +};
> +
>  /*
>   * The classical Unix view for directory is that it is a linear array of
>   * (name, inode number) entries. Linux/VFS assumes this model as well.
> @@ -582,6 +587,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
>  	struct inode *dir = file_inode(file);
>  	struct ubifs_info *c = dir->i_sb->s_fs_info;
>  	bool encrypted = IS_ENCRYPTED(dir);
> +	struct ubifs_dir_data *data = file->private_data;
>  
>  	dbg_gen("dir ino %lu, f_pos %#llx", dir->i_ino, ctx->pos);
>  
> @@ -604,27 +610,27 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
>  		fstr_real_len = fstr.len;
>  	}
>  
> -	if (file->f_version == 0) {
> +	if (data->cookie == 0) {
>  		/*
> -		 * The file was seek'ed, which means that @file->private_data
> +		 * The file was seek'ed, which means that @data->dent
>  		 * is now invalid. This may also be just the first
>  		 * 'ubifs_readdir()' invocation, in which case
> -		 * @file->private_data is NULL, and the below code is
> +		 * @data->dent is NULL, and the below code is
>  		 * basically a no-op.
>  		 */
> -		kfree(file->private_data);
> -		file->private_data = NULL;
> +		kfree(data->dent);
> +		data->dent = NULL;
>  	}
>  
>  	/*
> -	 * 'generic_file_llseek()' unconditionally sets @file->f_version to
> -	 * zero, and we use this for detecting whether the file was seek'ed.
> +	 * 'ubifs_dir_llseek()' sets @data->cookie to zero, and we use this
> +	 * for detecting whether the file was seek'ed.
>  	 */
> -	file->f_version = 1;
> +	data->cookie = 1;
>  
>  	/* File positions 0 and 1 correspond to "." and ".." */
>  	if (ctx->pos < 2) {
> -		ubifs_assert(c, !file->private_data);
> +		ubifs_assert(c, !data->dent);
>  		if (!dir_emit_dots(file, ctx)) {
>  			if (encrypted)
>  				fscrypt_fname_free_buffer(&fstr);
> @@ -641,10 +647,10 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
>  		}
>  
>  		ctx->pos = key_hash_flash(c, &dent->key);
> -		file->private_data = dent;
> +		data->dent = dent;
>  	}
>  
> -	dent = file->private_data;
> +	dent = data->dent;
>  	if (!dent) {
>  		/*
>  		 * The directory was seek'ed to and is now readdir'ed.
> @@ -658,7 +664,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
>  			goto out;
>  		}
>  		ctx->pos = key_hash_flash(c, &dent->key);
> -		file->private_data = dent;
> +		data->dent = dent;
>  	}
>  
>  	while (1) {
> @@ -701,15 +707,15 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
>  			goto out;
>  		}
>  
> -		kfree(file->private_data);
> +		kfree(data->dent);
>  		ctx->pos = key_hash_flash(c, &dent->key);
> -		file->private_data = dent;
> +		data->dent = dent;
>  		cond_resched();
>  	}
>  
>  out:
> -	kfree(file->private_data);
> -	file->private_data = NULL;
> +	kfree(data->dent);
> +	data->dent = NULL;
>  
>  	if (encrypted)
>  		fscrypt_fname_free_buffer(&fstr);
> @@ -733,7 +739,10 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
>  /* Free saved readdir() state when the directory is closed */
>  static int ubifs_dir_release(struct inode *dir, struct file *file)
>  {
> -	kfree(file->private_data);
> +	struct ubifs_dir_data *data = file->private_data;
> +
> +	kfree(data->dent);
> +	kfree(data);
>  	file->private_data = NULL;
>  	return 0;
>  }
> @@ -1712,6 +1721,24 @@ int ubifs_getattr(struct mnt_idmap *idmap, const struct path *path,
>  	return 0;
>  }
>  
> +static int ubifs_dir_open(struct inode *inode, struct file *file)
> +{
> +	struct ubifs_dir_data	*data;
> +
> +	data = kzalloc(sizeof(struct ubifs_dir_data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +	file->private_data = data;
> +	return 0;
> +}
> +
> +static loff_t ubifs_dir_llseek(struct file *file, loff_t offset, int whence)
> +{
> +	struct ubifs_dir_data *data = file->private_data;
> +
> +	return generic_llseek_cookie(file, offset, whence, &data->cookie);
> +}
> +
>  const struct inode_operations ubifs_dir_inode_operations = {
>  	.lookup      = ubifs_lookup,
>  	.create      = ubifs_create,
> @@ -1732,7 +1759,9 @@ const struct inode_operations ubifs_dir_inode_operations = {
>  };
>  
>  const struct file_operations ubifs_dir_operations = {
> -	.llseek         = generic_file_llseek,
> +	.open		= ubifs_dir_open,
> +	.release	= ubifs_dir_release,
> +	.llseek         = ubifs_dir_llseek,
>  	.release        = ubifs_dir_release,
>  	.read           = generic_read_dir,
>  	.iterate_shared = ubifs_readdir,
> 
> -- 
> 2.45.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR