From: Hugh Dickins <hughd@google.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Zi Yan <ziy@nvidia.com>, John Hubbard <jhubbard@nvidia.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH mmotm] mm/vmstat: Add events for PMD based THP migration without split fix
Date: Thu, 21 May 2020 18:21:42 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.2005211812400.1524@eggly.anvils> (raw)
In-Reply-To: <f1673e4f-64ca-9cf2-861c-7e8a7deeede1@arm.com>
On Fri, 22 May 2020, Anshuman Khandual wrote:
> On 05/21/2020 07:19 PM, Hugh Dickins wrote:
> > Fix 5.7-rc6-mm1 page migration crash in unmap_and_move(): when the
> > page to be migrated has been freed from under us, that is considered
> > a MIGRATEPAGE_SUCCESS, but no newpage has been allocated (and I don't
> > think it would ever need to be counted as a successful THP migration).
> >
> > Signed-off-by: Hugh Dickins <hughd@google.com>
> > ---
> > Fix to mm-vmstat-add-events-for-pmd-based-thp-migration-without-split.patch
> >
> > mm/migrate.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > --- 5.7-rc6-mm1/mm/migrate.c 2020-05-20 12:21:56.117693827 -0700
> > +++ linux/mm/migrate.c 2020-05-20 15:08:12.319476978 -0700
> > @@ -1248,7 +1248,7 @@ out:
> > * we want to retry.
> > */
> > if (rc == MIGRATEPAGE_SUCCESS) {
> > - if (PageTransHuge(newpage))
> > + if (newpage && PageTransHuge(newpage))
> > thp_migration_success(true);
> > put_page(page);
> > if (reason == MR_MEMORY_FAILURE) {
> >
>
> Thanks Hugh. I am preparing to respin the vmstat patch accommodating some
> earlier comments. Wondering if I should also fold these changes here after
> adding your signed-off-by ?
Thanks for asking, but please just fold this one-line fixup into your
respin without my signed-off-by: I'm not heavily invested in these stats,
just want to avoid the crash; and don't know if I would want to sign the
result. You could add something like [hughd: fixed oops on NULL newpage]
to confirm that the fix is on board, but the fix is what matters.
Hugh
prev parent reply other threads:[~2020-05-22 1:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-21 13:49 [PATCH mmotm] mm/vmstat: Add events for PMD based THP migration without split fix Hugh Dickins
2020-05-21 18:54 ` Qian Cai
2020-05-21 19:48 ` Hugh Dickins
2020-05-22 0:46 ` Anshuman Khandual
2020-05-22 1:21 ` Hugh Dickins [this message]
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