Re: [Libguestfs] [PATCH] lib: Autodetect backing format and specify it explicitly.

On Thursday, 6 February 2020 18:20:19 CET Richard W.M. Jones wrote: > In the guestfs_disk_create API we have traditionally allowed you to > set backingfile without setting backingformat. The meaning of this is > to let qemu autodetect the backing format when opening the overlay > disk. > > However libvirt >= 6.0 refuses to even pass such disks to qemu (see > https://bugzilla.redhat.com/show_bug.cgi?id=1798148). > > For this reason, move the autodetection earlier and make it explicit. > We now autodetect the format of the backing disk at the time of > creation of the overlay, and set that as the backing format in the > overlay disk itself, allowing libvirt to open the disk later. > --- > lib/create.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/lib/create.c b/lib/create.c > index e2a59b88d..e30286c39 100644 > --- a/lib/create.c > +++ b/lib/create.c > @@ -255,6 +255,7 @@ disk_create_qcow2 (guestfs_h *g, const char *filename, int64_t size, > const struct guestfs_disk_create_argv *optargs) > { > const char *backingformat = NULL; > + CLEANUP_FREE char *backingformat_free = NULL; > const char *preallocation = NULL; > const char *compat = NULL; > int clustersize = -1; > @@ -302,6 +303,18 @@ disk_create_qcow2 (guestfs_h *g, const char *filename, int64_t size, > } > } > > + /* With libvirt >= 6.0 the backing format must be specified. */ > + if (backingfile != NULL && backingformat == NULL) { > + backingformat = backingformat_free = guestfs_disk_format (g, backingfile); > + if (!backingformat) > + return -1; > + if (STREQ (backingformat, "unknown")) { > + error (g, _("could not auto-detect the format of the backing file %s"), > + backingfile); > + return -1; > + } > + } I see this patch was pushed, even if it was not reviewed, and in general the problem was more (not totally) on libvirt side. Was it intentional?