From: Yang Shi <shy828301@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: syzbot <syzbot+1f52b3a18d5633fa7f82@syzkaller.appspotmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Alistair Popple <apopple@nvidia.com>,
chinwen.chang@mediatek.com, fgheet255t@gmail.com,
Jann Horn <jannh@google.com>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>, Peter Xu <peterx@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
syzkaller-bugs@googlegroups.com, tonymarislogistics@yandex.com,
Vlastimil Babka <vbabka@suse.cz>,
walken@google.com, Zi Yan <ziy@nvidia.com>
Subject: Re: [syzbot] kernel BUG in __page_mapcount
Date: Tue, 21 Dec 2021 11:07:03 -0800 [thread overview]
Message-ID: <CAHbLzkqYhtYNRs83DP-Cgti8-4kZn-iXHTdkesK+=U3d3N0U+w@mail.gmail.com> (raw)
In-Reply-To: <YcIfj3nfuL0kzkFO@casper.infradead.org>
On Tue, Dec 21, 2021 at 10:40 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Dec 21, 2021 at 10:24:27AM -0800, Yang Shi wrote:
> > It seems the THP is split during smaps walk. The reproducer does call
> > MADV_FREE on partial THP which may split the huge page.
> >
> > The below fix (untested) should be able to fix it.
>
> Did you read the rest of the thread on this? If the page is being
> migrated, we should still account it ... also, you've changed the
Yes, the being migrated pages may be skipped. We should be able to add
a new flag to smaps_account() to indicate this is a migration entry
then don't elevate the page count.
> refcount, so this:
>
> if (page_count(page) == 1) {
> smaps_page_accumulate(mss, page, size, size << PSS_SHIFT, dirty,
> locked, true);
> return;
> }
>
> will never trigger.
The get_page_unless_zero() is called after this block.
next prev parent reply other threads:[~2021-12-21 19:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <00000000000017977605c395a751@google.com>
2021-06-07 17:27 ` split_huge_page_to_list() races with page_mapcount() on migration entry in smaps code? [was: Re: [syzbot] kernel BUG in __page_mapcount] Jann Horn
2021-06-07 18:03 ` Matthew Wilcox
2021-06-07 19:55 ` Jann Horn
2021-06-07 20:20 ` Matthew Wilcox
2021-06-07 20:49 ` Kirill A. Shutemov
2021-12-21 17:24 ` [syzbot] kernel BUG in __page_mapcount syzbot
2021-12-21 18:24 ` Yang Shi
2021-12-21 18:40 ` Matthew Wilcox
2021-12-21 19:07 ` Yang Shi [this message]
2021-12-22 1:42 ` Yang Shi
2022-01-05 19:05 ` Yang Shi
2022-01-11 23:14 ` Yang Shi
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