lkml.org 
[lkml]   [2013]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/4] mm/migrate: correct return value of migrate_pages()
On 12/06/2013 09:41 AM, Joonsoo Kim wrote:
> migrate_pages() should return number of pages not migrated or error code.
> When unmap_and_move return -EAGAIN, outer loop is re-execution without
> initialising nr_failed. This makes nr_failed over-counted.
>
> So this patch correct it by initialising nr_failed in outer loop.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 3747fcd..1f59ccc 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1102,6 +1102,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>
> for(pass = 0; pass < 10 && retry; pass++) {
> retry = 0;
> + nr_failed = 0;
>
> list_for_each_entry_safe(page, page2, from, lru) {
> cond_resched();
>

If I'm reading the code correctly, unmap_and_move() (and
unmap_and_move_huge_page() as well) deletes all pages from the 'from'
list, unless it fails with -EAGAIN. So the only pages you see in
subsequent passes are those that failed with -EAGAIN and those are not
counted as nr_failed. So there shouldn't be over-count, but your patch
could result in under-count.

Perhaps a comment somewhere would clarify this.


\
 
 \ /
  Last update: 2013-12-06 16:01    [W:0.112 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site