When we have locked more than one folios, we cannot wait the lock or bit
(e.g., page lock, buffer head lock, writeback bit) synchronously. 
Otherwise deadlock may be triggered.  This make it hard to batch the
synchronous migration directly.

This patch re-enables batching synchronous migration via trying to migrate
in batch asynchronously firstly.  And any folios that are failed to be
migrated asynchronously will be migrated synchronously one by one.

Test shows that this can restore the TLB flushing batching performance for
synchronous migration effectively.

Link: https://lkml.kernel.org/r/20230303030155.160983-4-ying.huang@intel.com
Fixes: 5dfab109 ("migrate_pages: batch _unmap and _move")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Tested-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Xu, Pengfei" <pengfei.xu@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Stefan Roesch <shr@devkernel.io>
Cc: Tejun Heo <tj@kernel.org>
Cc: Xin Hao <xhao@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>