Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Fri, 13 May 2022 17:26:07 -0700
From:   Minchan Kim <minchan@kernel.org>
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        syzbot <syzbot+acf65ca584991f3cc447@syzkaller.appspotmail.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        llvm@lists.linux.dev, nathan@kernel.org, ndesaulniers@google.com,
        syzkaller-bugs@googlegroups.com, trix@redhat.com,
        Matthew Wilcox <willy@infradead.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        David Hildenbrand <david@redhat.com>
Subject: Re: [syzbot] WARNING in follow_hugetlb_page
Message-ID: <Yn73Hz7LkSUv7ycw@google.com>
References: <000000000000ef451a05dee0f2b1@google.com>
 <00000000000077377c05dee75f63@google.com>
 <20220513102617.c464c4f566052838e911a3ec@linux-foundation.org>
 <75f09063-d184-7d44-17a1-ed04be5eb953@oracle.com>
 <a7fd0c3f-921e-19b3-2f67-a231dede28f9@oracle.com>
 <20220513161910.d1b73583cdb2e33562aa86e5@linux-foundation.org>
 <Yn7vnpXwX50J3K+7@google.com>
 <4809b134-a37a-50b8-4c25-44548bc1048f@nvidia.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <4809b134-a37a-50b8-4c25-44548bc1048f@nvidia.com>
Precedence: bulk

On Fri, May 13, 2022 at 05:09:11PM -0700, John Hubbard wrote:
> On 5/13/22 16:54, Minchan Kim wrote:
> > > > I isolated this to Minchan Kim's "mm: fix is_pinnable_page against on cma
> > > > page".  Yes, the fat finger fix is in next-20220513.
> > > > 
> > > > I don't have time to analyze right now, but can confirm that in the
> > > > reproducer is_pinnable_page is returning false after this change when it
> > > > previously returned true.
> > > 
> > > OK, thanks, I dropped mm-fix-is_pinnable_page-against-on-cma-page.patch
> > 
> > Seems like bug of the patch v5 due to change of this
> > 
> >      if (mt & (MIGRATE_CMA | MIGRATE_ISOLATE))
> > 
> > The migration type is not bit type so it shold be
> > 
> > if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE)
> > 
> 
> Sorry for leading you astray by recommending the bitwise OR, Minchan.
> I overlooked that point even though it was right in front of me.

No worry, John.

Anything else further can we get insight from the warning?

For example, pin_user_pages going on against a hugetlb page
which are concurrently running alloc_contig_range(it's
exported function so anyone can call randomly) so
alloc_contig_range changes pageblock type as MIGRATE_ISOLATE
under us so the hit at the warning?