mm,hwpoison: return -EBUSY when migration fails

mainline inclusion
from mainline-v5.11-rc1
commit 3f4b815a
category: bugfix
bugzilla: 55077
CVE: NA

During LTP test, testcase 'move_pages12' failed. This is because
__soft_offline_page() will return -EIO when fail to migrate page.
This is not an error for 'move_pages12' but LTP treats 'return -EIO'
as an error.

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3f4b815a439adfb8f238335612c4b28bc10084d8

-------------------------------------------------

Currently, we return -EIO when we fail to migrate the page.

Migrations' failures are rather transient as they can happen due to
several reasons, e.g: high page refcount bump, mapping->migrate_page
failing etc.  All meaning that at that time the page could not be
migrated, but that has nothing to do with an EIO error.

Let us return -EBUSY instead, as we do in case we failed to isolate the
page.

While are it, let us remove the "ret" print as its value does not change.

Link: https://lkml.kernel.org/r/20201209092818.30417-1-osalvador@suse.de


Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Shixin Liu <liushixin2@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>