On Thu, 15 Nov 2018 10:41:40 -0800 p.jaroszynski@xxxxxxxxx wrote:
> migrate_page_move_mapping() expects pages with private data set to have
> a page_count elevated by 1. This is what used to happen for xfs through
> the buffer_heads code before the switch to iomap in commit 82cb14175e7d
> ("xfs: add support for sub-pagesize writeback without buffer_heads").
> Not having the count elevated causes move_pages() to fail on memory
> mapped files coming from xfs.
>
> Make iomap compatible with the migrate_page_move_mapping() assumption
> by elevating the page count as part of iomap_page_create() and lowering
> it in iomap_page_release().
What are the real-world end-user effects of this bug?
Is a -stable backport warranted?
