linux-kernel - Re: [PATCH] mm/page_alloc: avoid hard lockups in __alloc_pages

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Date:   Sat, 10 Jul 2021 22:10:03 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     qiang.zhang@...driver.com, mgorman@...hsingularity.net,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page_alloc: avoid hard lockups in __alloc_pages_bulk()

On Sat, Jul 10, 2021 at 11:46:13AM -0700, Andrew Morton wrote:
> On Sat, 10 Jul 2021 19:29:29 +0800 qiang.zhang@...driver.com wrote:
> 
> > From: Zqiang <qiang.zhang@...driver.com>
> > 
> > The __alloc_pages_bulk() mainly used for batch allocation of
> > order-0 pages, in the case of holding pagesets.lock, if too
> > many pages are required, maybe trigger hard lockup watchdog.
> 
> Ouch.  Has this been observed in testing?  If so, can you please share
> the kernel debug output from that event?

This should be fixed in the caller by asking for fewer pages.
The NFS and vmalloc cases have already been fixed for this.