linux-kernel - Re: [External] [PATCH 7/8] hugetlb: make free_huge

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Date:   Mon, 29 Mar 2021 09:49:16 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@....com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Waiman Long <longman@...hat.com>, Peter Xu <peterx@...hat.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Hillf Danton <hdanton@...a.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [External] [PATCH 7/8] hugetlb: make free_huge_page irq safe

On Sat 27-03-21 15:06:36, Muchun Song wrote:
> On Thu, Mar 25, 2021 at 8:29 AM Mike Kravetz <mike.kravetz@...cle.com> wrote:
> >
> > Commit c77c0a8ac4c5 ("mm/hugetlb: defer freeing of huge pages if in
> > non-task context") was added to address the issue of free_huge_page
> > being called from irq context.  That commit hands off free_huge_page
> > processing to a workqueue if !in_task.  However, as seen in [1] this
> > does not cover all cases.  Instead, make the locks taken in the
> > free_huge_page irq safe.
> >
> > This patch does the following:
> > - Make hugetlb_lock irq safe.  This is mostly a simple process of
> >   changing spin_*lock calls to spin_*lock_irq* calls.
> > - Make subpool lock irq safe in a similar manner.
> > - Revert the !in_task check and workqueue handoff.
> >
> > [1] https://lore.kernel.org/linux-mm/000000000000f1c03b05bc43aadc@google.com/
> >
> > Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> 
> The changes are straightforward.
> 
> Reviewed-by: Muchun Song <songmuchun@...edance.com>
> 
> Since this patchset aims to fix a real word issue. Should we add a Fixes
> tag?

Do we know since when it is possible to use hugetlb in the networking
context? Maybe this is possible since ever but I am wondering why the
lockdep started complaining only now. Maybe just fuzzing finally started
using this setup which nobody does normally.
-- 
Michal Hocko
SUSE Labs