linux-kernel - Re: [External] Re: [PATCH v2 4/6] mm: hugetlb: add return -EAGAIN for dissolve_free_huge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMZfGtWg0J5syATXMpP8RYOz=w0gJNYz_=UrT3ueMspQjNY7BQ@mail.gmail.com>
Date:   Thu, 7 Jan 2021 11:11:41 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [External] Re: [PATCH v2 4/6] mm: hugetlb: add return -EAGAIN for dissolve_free_huge_page

On Thu, Jan 7, 2021 at 1:07 AM Michal Hocko <mhocko@...e.com> wrote:
>
> On Wed 06-01-21 16:47:37, Muchun Song wrote:
> > When dissolve_free_huge_page() races with __free_huge_page(), we can
> > do a retry. Because the race window is small.
>
> Is this a bug fix or mere optimization. I have hard time to tell from
> the description.

It is optimization. Thanks.

>
> > Signed-off-by: Muchun Song <songmuchun@...edance.com>
> > ---
> >  mm/hugetlb.c | 26 +++++++++++++++++++++-----
> >  1 file changed, 21 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> [...]
> > @@ -1825,6 +1828,14 @@ int dissolve_free_huge_page(struct page *page)
> >       }
> >  out:
> >       spin_unlock(&hugetlb_lock);
> > +
> > +     /*
> > +      * If the freeing of the HugeTLB page is put on a work queue, we should
> > +      * flush the work before retrying.
> > +      */
> > +     if (unlikely(rc == -EAGAIN))
> > +             flush_work(&free_hpage_work);
>
> Is it safe to wait for the work to finish from this context?

Yes. It is safe.

>
> --
> Michal Hocko
> SUSE Labs