Re: [Patch v2 3/4] mm/migrate.c: check pagelist in move_pages_and_store_status()

Wei Yang
2020-01-29T00:46:53Z

On Tue, Jan 28, 2020 at 11:21:13AM +0100, David Hildenbrand wrote:
>On 22.01.20 02:16, Wei Yang wrote:
>> When pagelist is empty, it is not necessary to do the move and store.
>> Also it consolidate the empty list check in one place.
>>
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>> Acked-by: Michal Hocko <mhocko@suse.com>
>> ---
>> mm/migrate.c | 9 +++------
>> 1 file changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index a4d3bd6475e1..80d2bba57265 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1499,9 +1499,6 @@ static int do_move_pages_to_node(struct mm_struct *mm,
>> {
>> int err;
>>
>> - if (list_empty(pagelist))
>> - return 0;
>> -
>> err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
>> MIGRATE_SYNC, MR_SYSCALL);
>> if (err)
>> @@ -1589,6 +1586,9 @@ static int move_pages_and_store_status(struct mm_struct *mm, int node,
>> {
>> int err;
>>
>> + if (list_empty(pagelist))
>> + return 0;
>> +
>> err = do_move_pages_to_node(mm, pagelist, node);
>> if (err)
>> return err;
>> @@ -1676,9 +1676,6 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
>> current_node = NUMA_NO_NODE;
>> }
>> out_flush:
>> - if (list_empty(&pagelist))
>> - return err;
>
>
>Am I wrong or are you discarding an error here? (err could be !0)
>

This is not obvious in this code snippet. If you look into the source code, it
might help you get the whole picture.

The following comment says:

Make sure we do not overwrite the existing error

So we didn't eat error here.

>
>--
>Thanks,
>
>David / dhildenb

--
Wei Yang
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