Re: [PATCH 1/2] mm/filemap: fix find_lock_entries hang on 32-bit THP

[Matthew Wilcox]

On Wed, Apr 21, 2021 at 05:37:33PM -0700, Hugh Dickins wrote:
> -		if (!xa_is_value(page) && PageTransHuge(page))
> -			xas_set(&xas, page->index + thp_nr_pages(page));
> +		if (!xa_is_value(page) && PageTransHuge(page)) {
> +			unsigned int nr_pages = thp_nr_pages(page);
> +
> +			/* Final THP may cross MAX_LFS_FILESIZE on 32-bit */
> +			xas_set(&xas, page->index + nr_pages);
> +			if (xas.xa_index < nr_pages)
> +				break;
> +		}

Aargh.  We really need to get the multi-index support in; this works
perfectly when the xas_set() hack isn't needed any more.