linux-kernel - Re: [PATCH 2/3] xfs: convert perag lookup to xarray

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Message-ID: <ZroepUyYganq8UHJ@casper.infradead.org>
Date: Mon, 12 Aug 2024 15:39:33 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Christoph Hellwig <hch@....de>
Cc: Chandan Babu R <chandan.babu@...cle.com>,
	"Darrick J. Wong" <djwong@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/3] xfs: convert perag lookup to xarray

On Mon, Aug 12, 2024 at 08:31:01AM +0200, Christoph Hellwig wrote:
> @@ -1020,14 +1016,16 @@ xfs_reclaim_inodes_count(
>  	struct xfs_mount	*mp)
>  {
>  	struct xfs_perag	*pag;
> -	xfs_agnumber_t		ag = 0;
> +	unsigned long		index = 0;
>  	long			reclaimable = 0;
>  
> -	while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
> -		ag = pag->pag_agno + 1;
> +	rcu_read_lock();
> +	xa_for_each_marked(&mp->m_perags, index, pag, XFS_ICI_RECLAIM_TAG) {
> +		trace_xfs_reclaim_inodes_count(pag, _THIS_IP_);
>  		reclaimable += pag->pag_ici_reclaimable;
> -		xfs_perag_put(pag);
>  	}
> +	rcu_read_unlock();

Would you rather use xas_for_each_marked() here?  O(n) rather than
O(n.log(n)).

Other than that, looks like a straightforward and correct conversion.