[PATCH 0/3 V2] xfs: allow logical-sector sized O_DIRECT for any fs sector size

[Eric Sandeen]

Resend of the previous patch, now in 3 parts, incorporating some
of Dave's suggestions, and split up for SUPER-easy review.  ;)

I have explicitly not changed XFS_IOC_DIOINFO output for now; it
still reports the actual minimum sizes and alignments which will
be allowed by the filesystem (and block layer beneath it).

Thanks,
-Eric