linux-kernel - Re: [PATCH] mm/migrate: fix deadlock in migrate_pages

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Message-ID: <aa5ac560-1dcc-45b6-8e24-0e9cb59feb18@linux.alibaba.com>
Date: Fri, 16 Aug 2024 13:12:35 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: "Huang, Ying" <ying.huang@...el.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Gao Xiang <xiang@...nel.org>
Subject: Re: [PATCH] mm/migrate: fix deadlock in migrate_pages_batch() on
 large folios


Hi Andrew,

On 2024/8/16 13:02, Andrew Morton wrote:
> On Mon, 29 Jul 2024 09:58:02 +0800 Gao Xiang <hsiangkao@...ux.alibaba.com> wrote:
> 
>>> For the fix, I think that we should still respect migrate_mode because
>>> users may prefer migration success over blocking.
>>>
>>> @@ -1492,11 +1492,17 @@ static int unmap_and_move_huge_page(new_folio_t get_new_folio,
>>>    	return rc;
>>>    }
>>>    
>>> -static inline int try_split_folio(struct folio *folio, struct list_head *split_folios)
>>> +static inline int try_split_folio(struct folio *folio, struct list_head *split_folios,
>>> +				  enum migrate_mode mode)
>>>    {
>>>    	int rc;
>>>    
>>> -	folio_lock(folio);
>>> +	if (mode == MIGRATE_ASYNC) {
>>> +		if (!folio_trylock(folio))
>>> +			return -EAGAIN;
>>> +	} else {
>>> +		folio_lock(folio);
>>> +	}
>>>    	rc = split_folio_to_list(folio, split_folios);
>>>    	folio_unlock(folio);
>>>    	if (!rc)
>>
>> Okay, yeah it looks better since it seems I missed the fallback
>> part in migrate_pages_sync().
>>
>> Let me send the next version to follow your advice, thanks.
> 
> The author seems to have disappeared.  Should we merge this as-is or
> does someone want to take a look at developing a v2?

I've replied your email last week, I'm not sure why it has not
been addressed?

https://lore.kernel.org/linux-mm/20240729021306.398286-1-hsiangkao@linux.alibaba.com/

The patch in your queue is already v2? No?

Thanks,
Gao Xiang