On 10/13/2012 03:59 PM, Eric Blake wrote:
When an image has no backing file, using VIR_STORAGE_FILE_AUTO for its type is a bit confusing. Additionally, a future patch would like to reserve a default value for the case of no file type specified in the XML, but different from the current use of -1 to imply probing, since probing is not always safe.
Also, a couple of file types were missing compared to supported code: libxl supports 'vhd', and qemu supports 'fat' for directories passed through as a file system.
+++ b/src/util/storage_file.c
@@ -335,8 +351,12 @@ qcowXGetBackingStore(char **res, * between the end of the header (QCOW2_HDR_TOTAL_SIZE) * and the start of the backingStoreName (offset) */ - if (isQCow2 && format) - qcow2GetBackingStoreFormat(format, buf, buf_size, QCOW2_HDR_TOTAL_SIZE, offset); + if (isQCow2 && format) { + qcow2GetBackingStoreFormat(format, buf, buf_size, QCOW2_HDR_TOTAL_SIZE, + offset); + if (*format <= VIR_STORAGE_FILE_NONE) + return BACKING_STORE_INVALID; + }
This breaks the case where a qcow2 file has a backing file but did not specify a format, and libvirt is set to allow probing (for example, if you use 'qemu-img rebase -u -b blah file' without '-F format'). I'm working on a fix. -- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org