On Thu, 10 Jan 2019, Dave Chinner wrote:

Sounds nice from a theoretical POV, but reality has taught us very 
different lessons.

FWIW, a quick check of XFS's history so you understand how long this 
behaviour has been around. It was introduced in the linux port in 2001 
as direct IO support was being added:

commit e837eac23662afae603aaaef7c94bc839c1b8f67
Author: Steve Lord [off-list ref]
Date:   Mon Mar 5 16:47:52 2001 +0000

    Add bounds checking for direct I/O, do the cache invalidation for
    data coherency on direct I/O.

Out of curiosity, which repository is this from please? Even google 
doesn't seem to know about this SHA.

Thanks,

-- 
Jiri Kosina
SUSE Labs