Re: [libvirt] [PATCH 3/4] Fix QEMU save/restore with block devices

On 04/21/2010 10:56 AM, 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 > > +++ b/src/qemu/qemu_driver.c > @@ -4789,6 +4789,7 @@ static int qemudDomainSaveFlag(virDomainPtr dom, const char *path, > qemuDomainObjPrivatePtr priv; > struct stat sb; > int is_bdev = 0; > + unsigned long long offset; Should this be off_t instead of ull? > @@ -1673,7 +1701,8 @@ int qemuMonitorJSONMigrateToCommand(qemuMonitorPtr mon, > goto cleanup; > } > > - 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) { Don't you still need to silence stderr, particularly since dd writes to stderr even on success? (2 instances)