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Date: Wed, 29 Nov 2023 21:07:56 -0800
From: Christoph Hellwig <hch@infradead.org>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 2/5] xfs: repair inode fork block mapping data structures
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On Fri, Nov 24, 2023 at 03:53:25PM -0800, Darrick J. Wong wrote:
> +static int
> +xrep_bmap_extent_cmp(
> +	const void			*a,
> +	const void			*b)
> +{
> +	xfs_fileoff_t			ao;
> +	xfs_fileoff_t			bo;
> +
> +	ao = xfs_bmbt_disk_get_startoff((struct xfs_bmbt_rec *)a);
> +	bo = xfs_bmbt_disk_get_startoff((struct xfs_bmbt_rec *)b);

It would be nice if we could just have local variables for the
xfs_bmbt_recs and not need casts.  I guess for that
xfs_bmbt_disk_get_startoff would need to take a const argument?

Probably something for later.

> +	if (whichfork == XFS_ATTR_FORK)
> +		return 0;

Nit: I'd probably just split the data fork specific validation
into a separate helper to keep things nicely organized.

> +	/*
> +	 * No need to waste time scanning for shared extents if the inode is
> +	 * already marked.
> +	 */
> +	if (whichfork == XFS_DATA_FORK && xfs_is_reflink_inode(sc->ip))
> +		rb->shared_extents = true;

The comment doesn't seem to match the code.

> +/*
> + * Try to reserve more blocks for a transaction.
> + *
> + * This is for callers that need to attach resources to a transaction, scan
> + * those resources to determine the space reservation requirements, and then
> + * modify the attached resources.  In other words, online repair.  This can
> + * fail due to ENOSPC, so the caller must be able to cancel the transaction
> + * without shutting down the fs.
> + */
> +int
> +xfs_trans_reserve_more(
> +	struct xfs_trans	*tp,
> +	unsigned int		blocks,
> +	unsigned int		rtextents)

This basically seems to duplicate xfs_trans_reserve except that it skips
the log reservation.  What about just allowing to pass a NULL resp
agument to xfs_trans_reserve to skip the log reservation and reuse the
code?

Otherwise this looks good to me.