linux-kernel - Re: [v2 PATCH] mm: move_pages: report the number of non-attempted pages

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Date:   Fri, 24 Jan 2020 07:44:08 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     Wei Yang <richardw.yang@...ux.intel.com>, mhocko@...e.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [v2 PATCH] mm: move_pages: report the number of non-attempted
 pages

On Thu, Jan 23, 2020 at 03:36:58PM -0800, Yang Shi wrote:
>
>
>On 1/23/20 2:59 PM, Wei Yang wrote:
>> On Thu, Jan 23, 2020 at 07:38:51AM +0800, Yang Shi wrote:
>> > Since commit a49bd4d71637 ("mm, numa: rework do_pages_move"),
>> > the semantic of move_pages() was changed to return the number of
>> > non-migrated pages (failed to migration) and the call would be aborted
>> > immediately if migrate_pages() returns positive value.  But it didn't
>> > report the number of pages that we even haven't attempted to migrate.
>> > So, fix it by including non-attempted pages in the return value.
>> > 
>> > Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move")
>> > Suggested-by: 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>
>> > ---
>> > v2: Rebased on top of the latest mainline kernel per Andrew
>> > 
>> > mm/migrate.c | 24 ++++++++++++++++++++++--
>> > 1 file changed, 22 insertions(+), 2 deletions(-)
>> > 
>> > diff --git a/mm/migrate.c b/mm/migrate.c
>> > index 86873b6..9b8eb5d 100644
>> > --- a/mm/migrate.c
>> > +++ b/mm/migrate.c
>> > @@ -1627,8 +1627,18 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
>> > 			start = i;
>> > 		} else if (node != current_node) {
>> > 			err = do_move_pages_to_node(mm, &pagelist, current_node);
>> > -			if (err)
>> > +			if (err) {
>> > +				/*
>> > +				 * Positive err means the number of failed
>> > +				 * pages to migrate.  Since we are going to
>> > +				 * abort and return the number of non-migrated
>> > +				 * pages, so need incude the rest of the
>> > +				 * nr_pages that have not attempted as well.
>> > +				 */
>> > +				if (err > 0)
>> > +					err += nr_pages - i - 1;
>> > 				goto out;
>> > +			}
>> > 			err = store_status(status, start, current_node, i - start);
>> > 			if (err)
>> > 				goto out;
>> > @@ -1659,8 +1669,11 @@ 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 += nr_pages - i - 1;
>> > 			goto out;
>> > +		}
>> > 		if (i > start) {
>> > 			err = store_status(status, start, current_node, i - start);
>> > 			if (err)
>> > @@ -1674,6 +1687,13 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
>> > 
>> > 	/* Make sure we do not overwrite the existing error */
>> > 	err1 = do_move_pages_to_node(mm, &pagelist, current_node);
>> > +	/*
>> > +	 * Don't have to report non-attempted pages here since:
>> In previous comment, you use "non-migrated". Here is "non-attempted". What's
>> the difference?
>
>In that comment "non-migrated" includes both reported by migrate_pages() and
>the non-attempted.
>

ok, I see the difference.

>> 
>> > +	 *     - If the above loop is done gracefully there is not non-attempted
>> > +	 *       page.
>> > +	 *     - If the above loop is aborted to it means more fatal error
>> > +	 *       happened, should return err.
>> > +	 */
>> > 	if (!err1)
>> > 		err1 = store_status(status, start, current_node, i - start);
>> > 	if (!err)
>> > -- 
>> > 1.8.3.1

-- 
Wei Yang
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