Re: [PATCH 10/10] xfs: cache unlinked pointers in an rhashtable

[Christoph Hellwig <hch@infradead.org>]

> +int xfs_iunlink_init(struct xfs_perag *pag);
> +void xfs_iunlink_destroy(struct xfs_perag *pag);
> +xfs_agino_t xfs_iunlink_lookup_backref(struct xfs_perag *pag,
> +		xfs_agino_t agino);
> +int xfs_iunlink_add_backref(struct xfs_perag *pag, xfs_agino_t prev_agino,
> +		xfs_agino_t this_agino);
> +int xfs_iunlink_change_backref(struct xfs_perag *pag, xfs_agino_t prev_agino,
> +		xfs_agino_t this_agino);

xfs_iunlink_lookup_backref and xfs_iunlink_change_backref aren't
used outside of xfs_inode.c and should be marked static.

> +	/*
> +	 * Make sure the in-core data knows about this unlinked inode.  Since
> +	 * our iunlinks recovery basically just deletes the head of a bucket
> +	 * list until the bucket is empty, we need only to add the backref from
> +	 * the current list item to the next one, if this isn't the list tail.
> +	 */
>  	pag = xfs_perag_get(mp, agno);
>  	pag->pagi_unlinked_count++;
> +	if (agino != NULLAGINO)
> +		error = xfs_iunlink_add_backref(pag, XFS_INO_TO_AGINO(mp, ino),
> +				agino);
>  	xfs_perag_put(pag);
> +	if (error)
> +		goto fail_iput;

Note that the previos agino that we recaculate above is actually passed
to the function as an argument.  I think we should just add a new
next_agino variable for the one we read from the dinode and return and
reuse the argument here instead of recaculating it.

Question: what lock now protects the rhastable modifications?  Maybe
we need to add some lockdep asserts to document that.