On Sat, Mar 3, 2018 at 1:40 AM, Andrew Morton akpm@linux-foundation.org wrote:
On Sat, 3 Mar 2018 01:12:26 +0100 Daniel Vacek neelx@redhat.com wrote:
Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns where possible") introduced a bug where move_freepages() triggers a VM_BUG_ON() on uninitialized page structure due to pageblock alignment.
b92df1de5d28 was merged a year ago. Can you suggest why this hasn't been reported before now?
Yeah. I was surprised myself I couldn't find a fix to backport to RHEL. But actually customers started to report this as soon as 7.4 (where b92df1de5d28 was merged in RHEL) was released. I remember reports from September/October-ish times. It's not easily reproduced and happens on a handful of machines only. I guess that's why. But that does not make it less serious, I think.
Though there actually is a report here: https://bugzilla.kernel.org/show_bug.cgi?id=196443
And there are reports for Fedora from July: https://bugzilla.redhat.com/show_bug.cgi?id=1473242 and CentOS: https://bugs.centos.org/view.php?id=13964 and we internally track several dozens reports for RHEL bug https://bugzilla.redhat.com/show_bug.cgi?id=1525121
Enough? ;-)
This makes me wonder whether a -stable backport is really needed...
For some machines it definitely is. Won't hurt either, IMHO.
--nX