From: sunqiuyang <sunqiuyang@huawei.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: RE: [PATCH 1/1] mm/migrate: fix list corruption in migration of non-LRU movable pages
Date: Thu, 5 Sep 2019 01:44:12 +0000 [thread overview]
Message-ID: <157FC541501A9C4C862B2F16FFE316DC190C5990@dggeml512-mbx.china.huawei.com> (raw)
In-Reply-To: <20190904125226.GV3838@dhcp22.suse.cz>
________________________________________
From: Michal Hocko [mhocko@kernel.org]
Sent: Wednesday, September 04, 2019 20:52
To: sunqiuyang
Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org
Subject: Re: [PATCH 1/1] mm/migrate: fix list corruption in migration of non-LRU movable pages
On Wed 04-09-19 12:19:11, sunqiuyang wrote:
> > Do not top post please
> >
> > On Wed 04-09-19 07:27:25, sunqiuyang wrote:
> > > isolate_migratepages_block() from another thread may try to isolate the page again:
> > >
> > > for (; low_pfn < end_pfn; low_pfn++) {
> > > /* ... */
> > > page = pfn_to_page(low_pfn);
> > > /* ... */
> > > if (!PageLRU(page)) {
> > > if (unlikely(__PageMovable(page)) && !PageIsolated(page)) {
> > > /* ... */
> > > if (!isolate_movable_page(page, isolate_mode))
> > > goto isolate_success;
> > > /*... */
> > > isolate_success:
> > > list_add(&page->lru, &cc->migratepages);
> > >
> > > And this page will be added to another list.
> > > Or, do you see any reason that the page cannot go through this path?
> >
> > The page shouldn't be __PageMovable after the migration is done. All the
> > state should have been transfered to the new page IIUC.
> >
>
> I don't see where page->mapping is modified after the migration is done.
>
> Actually, the last comment in move_to_new_page() says,
> "Anonymous and movable page->mapping will be cleard by
> free_pages_prepare so don't reset it here for keeping
> the type to work PageAnon, for example. "
>
> Or did I miss something? Thanks,
This talks about mapping rather than flags stored in the mapping.
I can see that in tree migration handlers (z3fold_page_migrate,
vmballoon_migratepage via balloon_page_delete, zs_page_migrate via
reset_page) all reset the movable flag. I am not sure whether that is a
documented requirement or just a coincidence. Maybe it should be
documented. I would like to hear from Minchan.
---
I checked the three migration handlers and only found __ClearPageMovable,
which clears registered address_space val with keeping PAGE_MAPPING_MOVABLE flag,
so the page should still be __PageMovable when caught by another migration thread. Right?
---
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-09-05 1:44 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-03 8:27 [PATCH 1/1] mm/migrate: fix list corruption in migration of non-LRU movable pages sunqiuyang
2019-09-03 13:17 ` Michal Hocko
2019-09-04 2:18 ` sunqiuyang
2019-09-04 6:38 ` Michal Hocko
2019-09-04 7:27 ` sunqiuyang
2019-09-04 8:14 ` Michal Hocko
2019-09-04 12:19 ` sunqiuyang
2019-09-04 12:52 ` Michal Hocko
2019-09-05 1:44 ` sunqiuyang [this message]
2019-09-09 8:40 ` Michal Hocko
2019-09-12 17:21 ` Minchan Kim
2019-09-10 19:23 ` Minchan Kim
2019-09-10 19:31 ` Michal Hocko
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