linux-kernel - Re: [PATCH] mm: move_pages: fix the return value if there are not-migrated pages

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Date:   Sat, 18 Jan 2020 21:44:15 -0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Wei Yang <richardw.yang@...ux.intel.com>
Cc:     mhocko@...e.com, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] mm: move_pages: fix the return value if there are
 not-migrated pages



On 1/18/20 6:37 PM, Wei Yang wrote:
> On Sat, Jan 18, 2020 at 01:26:43PM +0800, Yang Shi wrote:
>> The do_move_pages_to_node() might return > 0 value, the number of pages
>> that are not migrated, then the value will be returned to userspace
>> directly.  But, move_pages() syscall would just return 0 or errno.  So,
>> we need reset the return value to 0 for such case as what pre-v4.17 did.
>>
>> Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move")
>> Cc: Michal Hocko <mhocko@...e.com>
>> Cc: Wei Yang <richardw.yang@...ux.intel.com>
>> Cc: <stable@...r.kernel.org>    [4.17+]
>> Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
>> ---
>> mm/migrate.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 86873b6..3e75432 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1659,8 +1659,11 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
>> 			goto out_flush;
>>
>> 		err = do_move_pages_to_node(mm, &pagelist, current_node);
>> -		if (err)
>> +		if (err) {
>> +			if (err > 0)
>> +				err = 0;
>> 			goto out;
>> +		}
>> 		if (i > start) {
>> 			err = store_status(status, start, current_node, i - start);
>> 			if (err)
>> -- 
>> 1.8.3.1
>
> Hey, I am afraid you missed something. There are three calls of
> do_move_pages_to_node() in do_pages_move(). Why you just handle one return
> value? How about the other two?

A late night patch... I just simply missed those two. Thanks for 
catching it, will resolve in v2.

>