When fsync() runs wait_on_page_writeback_range() it only inspects pages which
are actually under I/O (PAGECACHE_TAG_WRITEBACK).  If a page completed I/O
prior to wait_on_page_writeback_range() looking at it, it is supposed to have
recorded its I/O error state in the address_space.

But mpage_mpage_end_io_write() forgot to set the address_space error flag in
this case.
Signed-off-by: Qu Fuping <fs@ercist.iscas.ac.cn>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>