Fix a bug on error handling in the direct I/O function.

Currently, if a file is opened with the O_DIRECT|O_SYNC flag, the write()
syscall cannot receive the EIO error after an I/O error (SCSI cable is
disconnected etc.).

Return values of other points that call generic_osync_inode() are treated
appropriately.
Signed-off-by: Hisashi Hifumi  <hifumi.hisashi@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>