Re: [Qemu-devel] [PATCH 0/2] block/file-posix: Fix fully preallocated truncate

[Eric Blake <eblake@redhat.com>]

On 02/28/2018 07:13 AM, 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

Good catch.  Series:
Reviewed-by: Eric Blake <eblake@redhat.com>

gluster.c has similar code, but it assigns glfs_lseek() to an int64_t, 
so it does not have the bug.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org