Messages in this thread | | | Subject | Re: [PATCH v3] mm/page_isolation: guard against possible putback unisolated page | From | Miaohe Lin <> | Date | Wed, 15 Sep 2021 14:37:46 +0800 |
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On 2021/9/15 10:09, Andrew Morton wrote: > On Tue, 14 Sep 2021 19:45:08 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote: > >> Isolating a free page in an isolated pageblock is expected to always work >> as watermarks don't apply here. But if __isolate_free_page() failed, due >> to condition changes, the page will be left on the free list. And the page >> will be put back to free list again via __putback_isolated_page(). This may >> trigger VM_BUG_ON_PAGE() on page->flags checking in __free_one_page() if >> PageReported is set. Or we will corrupt the free list because list_add() >> will be called for pages already on another list. Add a VM_WARN_ON() to >> complain about this change. > > Are you able to identify a Fixes: here? >
Sure, this should be "Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock")."
> Is a cc:stable justified?
I'm afraid not. As David pointed out, ""
In unset_migratetype_isolate() we check that is_migrate_isolate_page(page) holds, otherwise we return.
We call __isolate_free_page() only for such pages.
__isolate_free_page() won't perform watermark checks on is_migrate_isolate().
Consequently, __isolate_free_page() should never fail when called from unset_migratetype_isolate()
""
In a nutshell, __isolate_free_page can not fail here. So it is harmless now and doesn't worth cc:stable.
Please see https://www.spinics.net/lists/linux-mm/msg269434.html for detail.
Many thanks.
> . >
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