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

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. This means that we need to pad the header + XML out to a multiple of dd block size (in this case we choose 512). 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 | 190 +++++++++++++++++++++++++----------------- src/qemu/qemu_monitor.c | 35 +++++++-- src/qemu/qemu_monitor.h | 11 ++- src/qemu/qemu_monitor_json.c | 37 ++++++++- src/qemu/qemu_monitor_json.h | 9 ++- src/qemu/qemu_monitor_text.c | 37 ++++++++- src/qemu/qemu_monitor_text.h | 9 ++- 7 files changed, 232 insertions(+), 96 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 41a516c..09b6493 100644 --- a/src/qemu/qemu_driver.c +++ 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_reg = 0; + unsigned long long offset; memset(&header, 0, sizeof(header)); memcpy(header.magic, QEMUD_SAVE_MAGIC, sizeof(header.magic)); @@ -4862,104 +4863,137 @@ static int qemudDomainSaveFlag(virDomainPtr dom, const char *path, hdata.path = path; hdata.xml = xml; hdata.header =&header; + offset = sizeof(header) + header.xml_len; + + /* Due to way we append QEMU state on our header with dd, + * we need to ensure there's a 512 byte boundary. Unfortunately + * we don't have an explicit offset in the header, so we fake + * it by padding the XML string with NULLs */ + if (offset % QEMU_MONITOR_MIGRATE_TO_FILE_BS) { + unsigned long long pad = + QEMU_MONITOR_MIGRATE_TO_FILE_BS - + (offset % QEMU_MONITOR_MIGRATE_TO_FILE_BS); + + if (VIR_REALLOC_N(xml, header.xml_len + pad)< 0) { + virReportOOMError(); + goto endjob; + } + memset(xml + header.xml_len, 0, pad); + offset += pad; + header.xml_len += pad; + }