[PATCH] mm: move_pages: report the number of non-attempted pages

Yang Shi
2020-01-22T19:40:04Z

Since commit a49bd4d71637 ("mm, numa: rework do_pages_move"),
the semantic of move_pages() was changed to return the number of
non-migrated pages (failed to migration) and the call would be aborted
immediately if migrate_pages() returns positive value. But it didn't
report the number of pages that we even haven't attempted to migrate.
So, fix it by including non-attempted pages in the return value.

Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move")
Suggested-by: Michal Hocko <mhocko@suse.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: <stable@vger.kernel.org> [4.17+]
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
---
The patch is based off Wei Yang's cleanup patchset:
https://lore.kernel.org/linux-mm/20200122011647.13636-1-richardw.yang@linux.intel.com/T/#t

mm/migrate.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 591f2e5..51b1b76 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1582,7 +1582,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,

static int move_pages_and_store_status(struct mm_struct *mm, int node,
struct list_head *pagelist, int __user *status,
- int start, int nr)
+ int start, int nr, unsigned long total)
{
int err;

@@ -1590,8 +1590,17 @@ static int move_pages_and_store_status(struct mm_struct *mm, int node,
return 0;

err = do_move_pages_to_node(mm, pagelist, node);
- if (err)
+ if (err) {
+ /*
+ * Possitive err means the number of failed pages to
+ * migrate. Since we are going to abort and return the
+ * number of non-migrated pages, so need incude the rest
+ * of the nr_pages that are not attempted as well.
+ */
+ if (err > 0)
+ err += total - start - nr - 1;
return err;
+ }
err = store_status(status, start, node, nr);
return err;
}
@@ -1640,7 +1649,8 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
start = i;
} else if (node != current_node) {
err = move_pages_and_store_status(mm, current_node,
- &pagelist, status, start, i - start);
+ &pagelist, status, start, i - start,
+ nr_pages);
if (err)
goto out;
start = i;
@@ -1670,7 +1680,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
goto out_flush;

err = move_pages_and_store_status(mm, current_node, &pagelist,
- status, start, i - start);
+ status, start, i - start, nr_pages);
if (err)
goto out;
current_node = NUMA_NO_NODE;
@@ -1678,7 +1688,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
out_flush:
/* Make sure we do not overwrite the existing error */
err1 = move_pages_and_store_status(mm, current_node, &pagelist,
- status, start, i - start);
+ status, start, i - start, nr_pages);
if (err >= 0)
err = err1;
out:
--
1.8.3.1