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

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Message-ID: <20200119023720.GD9745@richard>
Date:   Sun, 19 Jan 2020 10:37:20 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     mhocko@...e.com, richardw.yang@...ux.intel.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 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?

-- 
Wei Yang
Help you, Help me