On 2021/7/19 19:59, Oleksandr Natalenko wrote:
> On pondělí 19. července 2021 13:50:07 CEST Miaohe Lin wrote:
>> On 2021/7/19 19:22, Matthew Wilcox wrote:
>>> On Mon, Jul 19, 2021 at 07:12:58PM +0800, Miaohe Lin wrote:
>>>> When in the commit 2799e77529c2a, we're using the percpu_ref to serialize
>>>> against concurrent swapoff, i.e. there's percpu_ref inside
>>>> get_swap_device() instead of rcu_read_lock(). Please see commit
>>>> 63d8620ecf93 ("mm/swapfile: use percpu_ref to serialize against
>>>> concurrent swapoff") for detail.
>>>
>>> Oh, so this is a backport problem. 2799e77529c2 was backported without
>>> its prerequisite 63d8620ecf93. Greg, probably best to just drop
>>
>> Yes, they're posted as a patch set:
>>
>> https://lkml.kernel.org/r/20210426123316.806267-1-linmiaohe@xxxxxxxxxx
>>
>>> 2799e77529c2 from all stable trees; the race described is not very
>>> important (swapoff vs reading a page back from that swap device).
>>> .
>>
>> The swapoff races with reading a page back from that swap device should be
>> really uncommon as most users only do swapoff when the system is going to
>> shutdown.
>>
>> Sorry for the trouble!
>
> git log --oneline v5.13..v5.13.3 --author="Miaohe Lin"
> 11ebc09e50dc mm/zswap.c: fix two bugs in zswap_writeback_entry()
> 95d192da198d mm/z3fold: use release_z3fold_page_locked() to release locked
> z3fold page
> ccb7848e2344 mm/z3fold: fix potential memory leak in z3fold_destroy_pool()
> 9f7229c901c1 mm/huge_memory.c: don't discard hugepage if other processes are
> mapping it
> f13259175e4f mm/huge_memory.c: add missing read-only THP checking in
> transparent_hugepage_enabled()
> afafd371e7de mm/huge_memory.c: remove dedicated macro HPAGE_CACHE_INDEX_MASK
> a533a21b692f mm/shmem: fix shmem_swapin() race with swapoff
> c3b39134bbd0 swap: fix do_swap_page() race with swapoff
>
> Do you suggest reverting "mm/shmem: fix shmem_swapin() race with swapoff" as
> well?
This patch also rely on its prerequisite 63d8620ecf93. I think we should either revert
any commit in this series or just backport the entire series.
Many thanks.
>
