linux-kernel - Re: [PATCH 6/6] mm/z3fold: use release_z3fold_page

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Date:   Tue, 22 Jun 2021 21:49:36 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Hillf Danton <hdanton@...a.com>
CC:     <akpm@...ux-foundation.org>, <vitalywool@...il.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
Subject: Re: [PATCH 6/6] mm/z3fold: use release_z3fold_page_locked() to
 release locked z3fold page

On 2021/6/20 8:26, Hillf Danton wrote:
> On Sat, 19 Jun 2021 17:31:51 +0800 Miaohe Lin wrote:
>> We should use release_z3fold_page_locked() to release z3fold page when it's
>> locked, although it looks harmless to use release_z3fold_page() now.
>>
>> Fixes: dcf5aedb24f8 ("z3fold: stricter locking and more careful reclaim")
>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>> ---
>>  mm/z3fold.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/z3fold.c b/mm/z3fold.c
>> index 196d886a3436..b3c0577b8095 100644
>> --- a/mm/z3fold.c
>> +++ b/mm/z3fold.c
>> @@ -1372,7 +1372,7 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
>>  			if (zhdr->foreign_handles ||
>>  			    test_and_set_bit(PAGE_CLAIMED, &page->private)) {
>>  				if (kref_put(&zhdr->refcount,
>> -						release_z3fold_page))
>> +						release_z3fold_page_locked))
>>  					atomic64_dec(&pool->pages_nr);
> 
> LGTM. JFYI other issue in z3fold was reported [1] and if the fix proposed there
> makes any sense to you feel free to pick it up and ask Mike for his tests.
> 

Thank you for review and reply.

I browsed [1] several times but I failed to figure out what's the root cause. And I found
some bugs and possible race windows from previous code inspection. I think we can try fix
these first and see whether [1] is (hopefully) fixed. :)
Thanks again.

> [1] https://lore.kernel.org/linux-mm/20210316061351.1649-1-hdanton@sina.com/
> .
>