Re: Bug#561225: coreutils: cp --reflink fails with Btrfs file system

[Jason White]

>From discussion on the Btrfs list, the reason for this behaviour is that, if
the file is empty (thus containing no data extents) the ioctl() call returns
EINVAL.

It has been suggested on the Btrfs list that it should return success instead,
so that the caller doesn't have to check for the empty file case.

The problem originally arose for me when I attempted cp -r --reflink directory
/tmp/destination
where directory contained what turned out, on inspection, to be empty files (I
didn't realize these were all empty files - it was a source code tree from a
project I downloaded.)