Re: [PATCH 3/4] XFS: Return case-insensitive match for dentry cache

[Christoph Hellwig <hch@infradead.org>]

On Tue, May 20, 2008 at 12:24:57PM +1000, Barry Naujok wrote:
> +/**
> + * d_drop_neg_children - drop negative child dentries
> + * @parent: parent dentry
> + *
> + * Searches the children of the @parent dentry for negative dentries and
> + * drops them as they are found.
> + *
> + * This is primarily useful for case-insensitive filesystems to drop these
> + * entries when a new entry is created in the parent. The new entry must
> + * be instantiated before calling this function.
> + */
> +
> +void d_drop_neg_children(struct dentry *parent)

please spell out the negative :)  also no empty line between the
kerneldoc sand the actual function please.

> +{
> +	struct dentry *dentry;
> +
> +	spin_lock(&dcache_lock);
> +	list_for_each_entry(dentry, &parent->d_subdirs, d_u.d_child) {
> +		if (!dentry->d_inode) {
> +			spin_lock(&dentry->d_lock);
> +			__d_drop(dentry);
> +			spin_unlock(&dentry->d_lock);
> +			cond_resched_lock(&dcache_lock);

The cond_resched_lock here is not safe here, because the pointer you
are going to dereference in list_for_each_entry might not be valid
anymore.  This should look more like:

void d_drop_negative_children(struct dentry *parent)
{
	struct dentry *dentry;

 again:
	spin_lock(&dcache_lock);
	list_for_each_entry(dentry, &parent->d_subdirs, d_u.d_child) {
		if !dentry->d_inode)
			continue;

		spin_lock(&dentry->d_lock);
		__d_drop(dentry);
		spin_unlock(&dentry->d_lock);

		if (need_resched()) {
			spin_unlock(&dcache_lock);
			cond_resched();
			goto again;
		}
	}
	spin_unlock(&dcache_lock);
}


Btw, any reason you haven't commited patches 1 and 2 yet?  Also maybe
splitting 3 and 4 differently with one patch for the two new functions
in dcache.c and one for the full XFS ascii CI support might be best.