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@veillard.com | Rpmfind RPM search engine http://rpmfind.net/ http://veillard.com/ | virtualization library http://libvirt.org/