Re: Patch "khugepaged: khugepaged_test_exit() check mmget_still_valid()" has been added to the 5.8-stable tree

Sasha Levin
2020-08-26T21:46:27Z

On Wed, Aug 26, 2020 at 11:53:24AM -0700, Hugh Dickins wrote:
>On Mon, 24 Aug 2020, Hugh Dickins wrote:
>> On Sat, 22 Aug 2020, Hugh Dickins wrote:
>> > On Sat, 22 Aug 2020, Sasha Levin wrote:
>> > >
>> > > I've followed your instructions and backported the patches:
>> > >
>> > > bbe98f9cadff ("khugepaged: khugepaged_test_exit() check
>> > > mmget_still_valid()") - to all branches.
>> > > f3f99d63a815 ("khugepaged: adjust VM_BUG_ON_MM() in
>> > > __khugepaged_enter()") - to all branches.
>> > > 59ea6d06cfa9 ("coredump: fix race condition between collapse_huge_page()
>> > > and core dumping") - for 4.4.
>> >
>> > That's saved me time, thanks a lot for doing that work, Sasha.
>> >
>> > I've checked the results (haha, read on) and they're all fine,
>> > but one minor flaw in bisectability: the added 4.4 backport of
>> > "coredump: fix race condition..." adds a line (deleted by the next commit)
>> > result = SCAN_ANY_PROCESS;
>> > but neither "result" nor "SCAN_ANY_PROCESS" is defined in that tree,
>> > so that intermediate step would generate an easily fixed build error.
>> >
>> > FWIW - I don't know whether that's something to care about or not.
>>
>> Ah, but I missed that this one that we originally held back from 5.8,
>> did not in fact get re-added to 5.8: all the backport series have it,
>> but today's 5.8.4-rc1 does not have it.
>>
>> That's not a disaster - the series builds without it, and having its
>> fix without the fixed commit is just odd, no more unsafe than before;
>> but it should be re-added for a 5.8.4-rc2 or 5.8.5.
>
>I see 5.8 is at 5.8.5-rc1 today, but the commit below still missing:
>please re-add it, then we can all forget about it at last - thanks!

Greg went for a fast release cycle and I didn't have time to queue it
up, sorry. But don't worry - this patch isn't forgotten, I'll queue it
for the next release on Friday/Saturday.

--
Thanks,
Sasha