Re: [Qemu-devel] [PATCH 1/7] block: only force IO completion in .bdrv_truncate if we are shrinking

[Paolo Bonzini]

Il 06/03/2013 19:14, Jeff Cody ha scritto:
> QCOW breaks with it using a normal raw posix file as a device.  As a
> test: qemu-img create -f qcow test.qcow 5G.  Now run qemu with that
> drive mounted, and try to partition and format it.  QEMU now asserts.
> 
> The nicety of being able to using truncate during a write call,
> especially for VHDX (which can have relatively large block/cluster
> sizes), so to grow the file sparsely in a dynamically allocated file.

Perhaps we need two APIs, "truncate" and "revalidate".

Truncate should be a no-op if (!bs->growable).

Revalidate could be called by the block_resize monitor command with no
size specified.

Paolo