Re: v5.1-rc5 s390x WARNING

Matthew Wilcox
2019-04-18T14:37:18Z

On Thu, Apr 18, 2019 at 02:54:52PM +0100, Mel Gorman wrote:
> > > [ 1422.124060] WARNING: CPU: 0 PID: 9783 at mm/page_alloc.c:3777 __alloc_pages_irect_compact+0x182/0x190

We lost a character here? "_irect_" should surely be "_direct_"

> ---8<---
> mm, page_alloc: Always use a captured page regardless of compaction result
>
> During the development of commit 5e1f0f098b46 ("mm, compaction: capture
> a page under direct compaction"), a paranoid check was added to ensure
> that if a captured page was available after compaction that it was
> consistent with the final state of compaction. The intent was to catch
> serious programming bugs such as using a stale page pointer and causing
> corruption problems.
>
> However, it is possible to get a captured page even if compaction was
> unsuccessful if an interrupt triggered and happened to free pages in
> interrupt context that got merged into a suitable high-order page. It's
> highly unlikely but Li Wang did report the following warning on s390
>
> [ 1422.124060] WARNING: CPU: 0 PID: 9783 at mm/page_alloc.c:3777 __alloc_pages_irect_compact+0x182/0x190

... so it probably needs to be corrected here.