On Thu, Apr 22, 2010 at 11:36:06AM +0100, Daniel P. Berrange wrote:
> On Wed, Apr 21, 2010 at 11:02:33PM +0200, Daniel Veillard wrote:
> > On Wed, Apr 21, 2010 at 05:56:12PM +0100, Daniel P. Berrange wrote:
> > > The save process was relying on use of the shell >> append
> > > operator to ensure the save data was placed after the libvirt
> > > header + XML. This doesn't work for block devices though.
> > > Replace this code with use of 'dd' and its 'seek' parameter.
> > >
> > > The qemuMonitorMigateToCommand() monitor API is used for both
> > > save/coredump, and migration via UNIX socket. We can't simply
> > > switch this to use 'dd' since this causes problems with the
> > > migration usage. Thus, create a dedicated qemuMonitorMigateToFile
> > > which can accept an filename + offset, and remove the filename
> > > from the current qemuMonitorMigateToCommand() API
> > >
> > > * src/qemu/qemu_driver.c: Switch to qemuMonitorMigateToFile
> > > for save and core dump
> > > * src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h,
> > > src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_json.h,
> > > src/qemu/qemu_monitor_text.c, src/qemu/qemu_monitor_text.h: Create
> > > a new qemuMonitorMigateToFile, separate from the existing
> > > qemuMonitorMigateToCommand to allow handling file offsets
> > > ---
> > > src/qemu/qemu_driver.c | 172 +++++++++++++++++++++++-------------------
> > > src/qemu/qemu_monitor.c | 28 ++++++--
> > > src/qemu/qemu_monitor.h | 9 ++-
> > > src/qemu/qemu_monitor_json.c | 35 ++++++++-
> > > src/qemu/qemu_monitor_json.h | 9 ++-
> > > src/qemu/qemu_monitor_text.c | 35 ++++++++-
> > > src/qemu/qemu_monitor_text.h | 9 ++-
> > > 7 files changed, 201 insertions(+), 96 deletions(-)
> > >
> > [...]
> > >
> > > - if (virAsprintf(&dest, "exec:%s >>%s 2>/dev/null", argstr, safe_target) < 0) {
> > > + if (virAsprintf(&dest, "exec:%s | dd of=%s seek=%llub",
> > > + argstr, safe_target, offset) < 0) {
> >
> > hum %llu will be converted to the value and then 'b' is appended. But
> > my reading is that 'b' means block i.e. 512 bytes, and what we need is
> > skeep to offset bytes, i.e. use seek=%lluc since 'c' means characters,
> > or am I mistaken ?
>
> Hmm, yes I think you are correct. Oddly QEMU was happy enough restoring
> from this.
I assume dd will just push at the end if the offset is greater than the
file size instead of creating a sparse file, so we end up with what we
expect :-)
Daniel
--
Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
daniel@xxxxxxxxxxxx | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library http://libvirt.org/
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list