linux-kernel - Re: [PATCH v2] mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb

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Message-Id: <20240422142115.25582386f7f02df817eab8ae@linux-foundation.org>
Date: Mon, 22 Apr 2024 14:21:15 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Miaohe Lin <linmiaohe@...wei.com>
Cc: <muchun.song@...ux.dev>, <mike.kravetz@...cle.com>, <osalvador@...e.de>,
 <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when
 dissolve_free_hugetlb_folio()

On Sat, 20 Apr 2024 10:13:06 +0800 Miaohe Lin <linmiaohe@...wei.com> wrote:

> On 2024/4/20 5:11, Andrew Morton wrote:
> > On Fri, 19 Apr 2024 16:58:19 +0800 Miaohe Lin <linmiaohe@...wei.com> wrote:
> > 
> >> When I did memory failure tests recently, below warning occurs:
> >>
> >> DEBUG_LOCKS_WARN_ON(1)
> >> WARNING: CPU: 8 PID: 1011 at kernel/locking/lockdep.c:232 __lock_acquire+0xccb/0x1ca0
> >> Modules linked in: mce_inject hwpoison_inject
> >> CPU: 8 PID: 1011 Comm: bash Kdump: loaded Not tainted 6.9.0-rc3-next-20240410-00012-gdb69f219f4be #3
> >>
> >> ...
> >>
> >> --- a/mm/hugetlb.c
> >> +++ b/mm/hugetlb.c
> >> @@ -1773,7 +1773,7 @@ static void __update_and_free_hugetlb_folio(struct hstate *h,
> >>  	 * If vmemmap pages were allocated above, then we need to clear the
> >>  	 * hugetlb flag under the hugetlb lock.
> >>  	 */
> >> -	if (clear_flag) {
> >> +	if (folio_test_hugetlb(folio)) {
> >>  		spin_lock_irq(&hugetlb_lock);
> >>  		__folio_clear_hugetlb(folio);
> >>  		spin_unlock_irq(&hugetlb_lock);
> > 
> > Please let's prepare backportable fixes against current mainline, not
> > mm-unstable.  Because fixes against current -rcX and earlier will be
> > upstreamed ahead of the mm-unstable and mm-stable material.
> 
> Do you mean I need to send one fixup patch against mm-unstable and another
> one against current mainline?

Against mainline should suffice.  I normally fix up the subsequent
merge/build fallout.  If that gets too risky I'll ask for help or I'll
outright drop mm-unstable patches and shall ask for a redo of those. 
This is rare.