[patch 015/166] mm/migrate.c: unify "not queued for migration" handling in do_pages_move()

Andrew Morton
2020-04-07T03:04:21Z

From: Wei Yang <richardw.yang@linux.intel.com>
Subject: mm/migrate.c: unify "not queued for migration" handling in do_pages_move()

It can currently happen that we store the status of a page twice:
* Once we detect that it is already on the target node
* Once we moved a bunch of pages, and a page that's already on the
target node is contained in the current interval.

Let's simplify the code and always call do_move_pages_to_node() in case we
did not queue a page for migration. Note that pages that are already on
the target node are not added to the pagelist and are, therefore, ignored
by do_move_pages_to_node() - there is no functional change.

The status of such a page is now only stored once.

[david@redhat.com rephrase changelog]
Link: http://lkml.kernel.org/r/20200214003017.25558-5-richardw.yang@linux.intel.com
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/migrate.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

--- a/mm/migrate.c~mm-migratec-unify-not-queued-for-migration-handling-in-do_pages_move
+++ a/mm/migrate.c
@@ -1683,18 +1683,16 @@ static int do_pages_move(struct mm_struc
err = add_page_for_migration(mm, addr, current_node,
&pagelist, flags & MPOL_MF_MOVE_ALL);

- if (!err) {
- /* The page is already on the target node */
- err = store_status(status, i, current_node, 1);
- if (err)
- goto out_flush;
- continue;
- } else if (err > 0) {
+ if (err > 0) {
/* The page is successfully queued for migration */
continue;
}

- err = store_status(status, i, err, 1);
+ /*
+ * If the page is already on the target node (!err), store the
+ * node, otherwise, store the err.
+ */
+ err = store_status(status, i, err ? : current_node, 1);
if (err)
goto out_flush;

_