[PATCH v7 00/47] xfs: add reverse mapping support

[Dave Chinner]

On Fri, Aug 05, 2016 at 10:01:14AM +0300, Artem Bityutskiy wrote:
> On Fri, 2016-08-05 at 09:50 +1000, Dave Chinner wrote:
> > I'd much prefer that fiemap gives exact information about shared
> > extents. FIEMAP is a diagnostic tool and as such we need it to
> > accurately reflect the exact extent map of the inode being queried
> > so we aren't mislead about the layout of the file during trouble
> > shooting.
> 
> Hi Dave, you are right, and here is a side note:  we were using FIEMAP
> for optimizing image deployment in production, so it is a diagnostic
> tool and more.

Yay, data corruption ahoy!

Hasn't /anyone/ listened to the repeated statements from fs
developers that FIEMAP is not a safe method of optimising data
copying?

-Dave.
-- 
Dave Chinner
david at fromorbit.com