mm: migrate: return -ENOSYS if THP migration is unsupported

In the current implementation unmap_and_move() would return -ENOMEM if THP
migration is unsupported, then the THP will be split.  If split is failed
just exit without trying to migrate other pages.  It doesn't make too much
sense since there may be enough free memory to migrate other pages and
there may be a lot base pages on the list.

Return -ENOSYS to make consistent with hugetlb.  And if THP split is
failed just skip and try other pages on the list.

Just skip the whole list and exit when free memory is really low.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yang Shi <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions