linux-kernel - Re: [BUG] Crash on x86_32 for: mm: page_alloc: avoid merging non-fallbackable pageblocks with others

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Message-ID: <20220330165704.730be2b5@gandalf.local.home>
Date:   Wed, 30 Mar 2022 16:57:04 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Zi Yan <ziy@...dia.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        David Hildenbrand <david@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [BUG] Crash on x86_32 for: mm: page_alloc: avoid merging
 non-fallbackable pageblocks with others

On Wed, 30 Mar 2022 16:29:28 -0400
Zi Yan <ziy@...dia.com> wrote:

> In the original code, it will jump back to continue_merging and still tries
> to find the buddy. The crash means the found buddy is not valid, since its
> pageblock migratetype is NULL. That seems to suggest the physical memory
> range is not aligned to MAX_ORDER_NR_PAGES, which should not be the case.
> But if (!page_is_buddy(page, buddy, order)) prevents further buddy merging.
> I must be missing something.

Not sure if this matters or not, but my kernel command line has:

  crashkernel=256M

Could that have caused this to break?

-- Steve