If the blockdev doesn't implement BLKFLSBUF and returns -ENOTTY we should
still go ahead and perform the VFS-level sync.  We need to test for both
ENOTTY and EINVAL because some SCSI drivers incorrectly return EINVAL.
Signed-off-by: Ed L Cashin <ecashin@coraid.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>