Messages in this thread | | | Date | Fri, 06 Dec 2013 15:42:16 +0100 | From | Vlastimil Babka <> | Subject | Re: [PATCH 1/4] mm/migrate: correct return value of migrate_pages() |
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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.
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