Re: [Qemu-devel] Re: qemu disk on vfat

[Anthony Liguori]

Jim C. Brown wrote:
> Aactually, the bug is in vfat not in qemu-img.
>   

Not really.  POSIX doesn't mandate that ftruncate() increase a file 
size.  This is a Linux-ism and is only valid for filesystems that 
support holes (which vfat doesn't).

Regards,

Anthony Liguori

> qemu-img correctly uses ftruncate() which is suppose to make the file sparse
> if the underlying filesystem supports it, but it should fall back to adding 
> zeros
> to the end of the file. On vfat you aren't able to seek past the end of a file
> period, so this doesn't work.
>
> Probably qemu-img should just bail out in this case (as the other disk formats
> should work fine and you can always use dd). The 2nd patch I released does
> this - the error message just needs to be made more accurate.
>
>