Re: [PATCH v6] btrfs: Turn delayed_nodes_tree into an XArray

[Nikolay Borisov <nborisov@suse.com>]

On 26.04.22 г. 12:43 ч., Gabriel Niebler wrote:
> … in the btrfs_root struct and adjust all usages of this object to use the
> XArray API, because it is notionally easier to use and unserstand, as it
> provides array semantics, and also takes care of locking for us, further
> simplifying the code.
> 
> Also use the opportunity to do some light refactoring.
> 
> Signed-off-by: Gabriel Niebler <gniebler@suse.com>

<snip>

> @@ -1870,32 +1863,36 @@ void btrfs_kill_delayed_inode_items(struct btrfs_inode *inode)
>   
>   void btrfs_kill_all_delayed_nodes(struct btrfs_root *root)
>   {
> -	u64 inode_id = 0;
> +	unsigned long index = 0;
> +	struct btrfs_delayed_node *delayed_node;
>   	struct btrfs_delayed_node *delayed_nodes[8];
> -	int i, n;
>   
>   	while (1) {
> +		int n = 0;
> +
>   		spin_lock(&root->inode_lock);
> -		n = radix_tree_gang_lookup(&root->delayed_nodes_tree,
> -					   (void **)delayed_nodes, inode_id,
> -					   ARRAY_SIZE(delayed_nodes));
> -		if (!n) {
> +		if (xa_empty(&root->delayed_nodes)) {
>   			spin_unlock(&root->inode_lock);
> -			break;
> +			return;
>   		}
>   
> -		inode_id = delayed_nodes[n - 1]->inode_id + 1;
> -		for (i = 0; i < n; i++) {
> +		xa_for_each_start(&root->delayed_nodes, index,
> +				  delayed_node, index) {
>   			/*
>   			 * Don't increase refs in case the node is dead and
>   			 * about to be removed from the tree in the loop below
>   			 */
> -			if (!refcount_inc_not_zero(&delayed_nodes[i]->refs))
> -				delayed_nodes[i] = NULL;
> +			if (refcount_inc_not_zero(&delayed_node->refs)) {
> +				delayed_nodes[n] = delayed_node;
> +				n++;
> +			}
> +			if (n >= ARRAY_SIZE(delayed_nodes))
> +				break;
>   		}
> +		index++;
>   		spin_unlock(&root->inode_lock);
>   
> -		for (i = 0; i < n; i++) {
> +		for (int i = 0; i < n; i++) {
>   			if (!delayed_nodes[i])
>   				continue;

nit: This check now becomes redundant right, because the way n is 
modified we are guaranteed that everything from 0..n will actually be 
populated.

<snip>