Subject: Re: [PATCH RFC 03/24] vfs: add try_break_deleg calls for parents to vfs_{link,rename,unlink}

From: Al Viro <[email-masked]>
Date: Sat, 16 Mar 2024 23:57:17 +0000

On Fri, Mar 15, 2024 at 12:52:54PM -0400, Jeff Layton wrote:
> @@ -4603,9 +4606,12 @@ int vfs_link(struct dentry *old_dentry, struct mnt_idmap *idmap,
>  	else if (max_links && inode->i_nlink >= max_links)
>  		error = -EMLINK;
>  	else {
> -		error = try_break_deleg(inode, delegated_inode);
> -		if (!error)
> -			error = dir->i_op->link(old_dentry, dir, new_dentry);
> +		error = try_break_deleg(dir, delegated_inode);
> +		if (!error) {
> +			error = try_break_deleg(inode, delegated_inode);
> +			if (!error)
> +				error = dir->i_op->link(old_dentry, dir, new_dentry);
> +		}

A minor nit: that might be easier to follow as
		error = try_break_deleg(dir, delegated_inode);
		if (!error)
			error = try_break_deleg(inode, delegated_inode);
		if (!error)
			error = dir->i_op->link(old_dentry, dir, new_dentry);

and let the compiler deal with optimizing it - any C compiler is going to be
able to figure out that one out.  vfs_link() is a mix of those styles anyway -
we have
        if (!error && (inode->i_state & I_LINKABLE)) {
                spin_lock(&inode->i_lock);
                inode->i_state &= ~I_LINKABLE;
                spin_unlock(&inode->i_lock);
        }
immediately afterwards; might as well make that consistent, especially since
you are getting more shallow nesting that way.