When using FAT on a block device which supports rw_page, we can hit
BUG_ON(!PageLocked(page)) in try_to_free_buffers().  This is because we
call clean_buffers() after unlocking the page we've written.  Introduce
a new clean_page_buffers() which cleans all buffers associated with a
page and call it from within bdev_write_page().

[akpm@linux-foundation.org: s/PAGE_SIZE/~0U/ per Linus and Matthew]
Link: http://lkml.kernel.org/r/20171006211541.GA7409@bombadil.infradead.orgSigned-off-by: NMatthew Wilcox <mawilcox@microsoft.com>
Reported-by: NToshi Kani <toshi.kani@hpe.com>
Reported-by: NOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Tested-by: NToshi Kani <toshi.kani@hpe.com>
Acked-by: NJohannes Thumshirn <jthumshirn@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>