On 2018-02-28 14:13, Max Reitz wrote:
> Fully preallocated truncation has a 50 % chance of working on images
> files over file-posix.  It works if $SIZE % 4G < 2G, and it fails
> otherwise.  To make things even more interesting, often you would not
> even notice because qemu reported success even though it did nothing
> (because after the successful lseek(), errno was still 0, so when the
> file-posix driver tried to return a negative error code, it actually
> reported success).
> 
> This issue is fixed by patch 1 in this series.  Thanks to Daniel for
> reporting!
> 
> 
> Max Reitz (2):
>   block/file-posix: Fix fully preallocated truncate
>   iotests: Test preallocated truncate of 2G image
> 
>  block/file-posix.c         |  5 +++--
>  tests/qemu-iotests/106     | 24 ++++++++++++++++++++++++
>  tests/qemu-iotests/106.out | 10 ++++++++++
>  3 files changed, 37 insertions(+), 2 deletions(-)

Applied to my block tree...  (*cough* *cough* -- I'm the worst when it
comes to keeping track of my own patches.)

Max