Re: [PATCH 3/4] fs/dcache: Avoid the try_lock loop in d_delete()

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Feb 16, 2018 at 04:09:32PM +0100, John Ogness wrote:
> +static bool dentry_lock_inode(struct dentry *dentry)
> +{
> +	struct inode *inode = dentry->d_inode;
> +
> +	lockdep_assert_held(&dentry->d_lock);
> +
> +	if (unlikely(!spin_trylock(&inode->i_lock))) {

	if (likely(spin_trylock(&inode->i_lock)))
		return true;

and then unindent by 1 stop the below code:

> +		rcu_read_lock();
> +		spin_unlock(&dentry->d_lock);
> +		spin_lock(&inode->i_lock);
> +		spin_lock(&dentry->d_lock);
> +		rcu_read_unlock();
> +
> +		/*
> +		 * @dentry->d_inode might have changed after dropping
> +		 * @dentry->d_lock. If so, release @inode->i_lock and
> +		 * signal the caller to restart the operation.
> +		 */
> +		if (unlikely(inode != dentry->d_inode)) {
> +			spin_unlock(&inode->i_lock);
> +			return false;
> +		}
> +	}
> +	return true;
> +}