The patch titled
Subject: mm: fix do_pages_move status handling
has been added to the -mm tree. Its filename is
mm-fix-do_pages_move-status-handling.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-fix-do_pages_move-status-handling.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-do_pages_move-status-handling.patch
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------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm: fix do_pages_move status handling
Li Wang has reported that LTP move_pages04 test fails with the current
tree:
LTP move_pages04:
TFAIL : move_pages04.c:143: status[1] is EPERM, expected EFAULT
The test allocates an array of two pages, one is present while the other
is not (resp. backed by zero page) and it expects EFAULT for the second
page as the man page suggests. We are reporting EPERM which doesn't make
any sense and this is a result of a bug from cf5f16b23ec9 ("mm: unclutter
THP migration").
do_pages_move tries to handle as many pages in one batch as possible so we
queue all pages with the same node target together and that corresponds to
[start, i] range which is then used to update status array.
add_page_for_migration will correctly notice the zero (resp. !present)
page and returns with EFAULT which gets written to the status. But if
this is the last page in the array we do not update start and so the last
store_status after the loop will overwrite the range of the last batch
with NUMA_NO_NODE (which corresponds to EPERM).
Fix this by simply bailing out from the last flush if the pagelist is
empty as there is clearly nothing more to do.
Link: http://lkml.kernel.org/r/20180418121255.334-1-mhocko@xxxxxxxxxx
Fixes: cf5f16b23ec9 ("mm: unclutter THP migration")
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reported-by: Li Wang <liwang@xxxxxxxxxx>
Tested-by: Li Wang <liwang@xxxxxxxxxx>
Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 3 +++
1 file changed, 3 insertions(+)
diff -puN mm/migrate.c~mm-fix-do_pages_move-status-handling mm/migrate.c
--- a/mm/migrate.c~mm-fix-do_pages_move-status-handling
+++ a/mm/migrate.c
@@ -1622,6 +1622,9 @@ static int do_pages_move(struct mm_struc
current_node = NUMA_NO_NODE;
}
out_flush:
+ if (list_empty(&pagelist))
+ return err;
+
/* Make sure we do not overwrite the existing error */
err1 = do_move_pages_to_node(mm, &pagelist, current_node);
if (!err1)
_
Patches currently in -mm which might be from mhocko@xxxxxxxx are
mm-fix-do_pages_move-status-handling.patch
mm-oom-docs-describe-the-cgroup-aware-oom-killer-fix-2.patch
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