On Wed, Apr 27, 2011 at 4:05 AM, Brad Campbell <lists2...@fnarfbargle.com> wrote: > I see there is a bug raised about the behaviour of qemu-img when used to > convert using an output backing file. It allocates every sector whether or > not it already exists in the output backing file.
Please post the link to the bug report. > Can someone verify these assumptions for me please? > - I can bdrv_open() a file that has a chain of backing files, and the > following is true : > - bdrv_read() returns the most recently allocated sector contents (or > 0) Correct. > - bdrv_is_allocated() will return false only if that sector is not > allocated in _any_ of the files in the chain Incorrect. It returns true if the sector is allocated in the top-most file, false otherwise. In other words bdrv_is_allocated() is flat, it does not traverse a chain of backing files. Stefan
