On Thu 04-03-21 10:22:51, Minchan Kim wrote:
[...]
> How about this?
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 238d0fc232aa..489e557b9390 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8481,7 +8481,8 @@ static inline void dump_migrate_failure_pages(struct list_head *page_list)
>
> /* [start, end) must belong to a single zone. */
> static int __alloc_contig_migrate_range(struct compact_control *cc,
> - unsigned long start, unsigned long end)
> + unsigned long start, unsigned long end,
> + bool nofail)
This sounds like a very bad idea to me. Your nofail definition might
differ from what we actually define as __GFP_NOFAIL but I do not think
this interface should ever promise anything that strong.
Sure movable, cma regions should effectively never fail but there will
never be any _guarantee_ for that.
Earlier in the discussion I have suggested dynamic debugging facility.
Documentation/admin-guide/dynamic-debug-howto.rst. Have you tried to
look into that direction?
> {
> /* This function is based on compact_zone() from compaction.c. */
> unsigned int nr_reclaimed;
> @@ -8522,7 +8523,8 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
> NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE);
> }
> if (ret < 0) {
> - dump_migrate_failure_pages(&cc->migratepages);
> + if (ret == -EBUSY && nofail)
> + dump_migrate_failure_pages(&cc->migratepages);
> putback_movable_pages(&cc->migratepages);
> return ret;
> }
> @@ -8610,7 +8612,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> * allocated. So, if we fall through be sure to clear ret so that
> * -EBUSY is not accidentally used or returned to caller.
> */
> - ret = __alloc_contig_migrate_range(&cc, start, end);
> + ret = __alloc_contig_migrate_range(&cc, start, end,
> + migratetype == CMA ||
> + zone_idx(cc.zone) == ZONE_MOVABLE);
> if (ret && ret != -EBUSY)
> goto done;
> ret =0;
--
Michal Hocko
SUSE Labs
