Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?)

[Andreas Dilger]

On 2011-04-15, at 6:50 PM, Dave Chinner <david at fromorbit.com> wrote:
> What you are suggesting is that FIEMAP needs to be page cache
> coherent, and that is far, far away from the intended use of the
> interface. Even consiering that you need to looking for active pages
> in the page cache when mapping extents say to me that you are
> doing something very wrong.
> 
> Unwritten extents remain unwritten until the data is physically
> written to them. Therefore, to change their state, you need to sync
> the data covering the range.

In that case, it means cp should just always use FIEMAP_FLAG_SYNC, which is fine. 

Cheers, Andreas