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Date:   Fri, 13 May 2022 17:09:11 -0700
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Subject: Re: [syzbot] WARNING in follow_hugetlb_page
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To:     Minchan Kim <minchan@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     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>
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From:   John Hubbard <jhubbard@nvidia.com>
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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.


thanks,
-- 
John Hubbard
NVIDIA