Re: [libvirt] [PATCHv4 06/15] qemu: allow simple domain save to use fd: protocol

This allows direct saves (no compression, no root-squash NFS) to use the more efficient fd: migration, which in turn avoids a race where qemu exec: migration can sometimes fail because qemu does a generic waitpid() that conflicts with the pclose() used by exec:. Further patches will solve compression and root-squash NFS. * src/qemu/qemu_driver.c (qemudDomainSaveFlag): Use new function when there is no compression. --- src/qemu/qemu_driver.c | 26 +++++++++++++++++++++++--- 1 files changed, 23 insertions(+), 3 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 2d11da8..c4d3c85 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -1790,6 +1790,7 @@ static int qemudDomainSaveFlag(struct qemud_driver *driver, virDomainPtr dom, int is_reg = 0; unsigned long long offset; virCgroupPtr cgroup = NULL; + virBitmapPtr qemuCaps = NULL; memset(&header, 0, sizeof(header)); memcpy(header.magic, QEMUD_SAVE_MAGIC, sizeof(header.magic)); @@ -1820,6 +1821,11 @@ static int qemudDomainSaveFlag(struct qemud_driver *driver, virDomainPtr dom, } } + if (qemuCapsExtractVersionInfo(vm->def->emulator, vm->def->os.arch, + NULL, + &qemuCaps) < 0) + goto endjob; + /* Get XML for the domain */ xml = virDomainDefFormat(vm->def, VIR_DOMAIN_XML_SECURE); if (!xml) { @@ -1980,10 +1986,23 @@ static int qemudDomainSaveFlag(struct qemud_driver *driver, virDomainPtr dom, if (header.compressed == QEMUD_SAVE_FORMAT_RAW) { const char *args[] = { "cat", NULL }; + /* XXX gross - why don't we reuse the fd already opened earlier */ + int fd = -1; + + if (qemuCapsGet(qemuCaps, QEMU_CAPS_MIGRATE_QEMU_FD) && + priv->monConfig->type == VIR_DOMAIN_CHR_TYPE_UNIX) + fd = open(path, O_WRONLY);

qemuDomainObjEnterMonitorWithDriver(driver, vm); - rc = qemuMonitorMigrateToFile(priv->mon, - QEMU_MONITOR_MIGRATE_BACKGROUND, - args, path, offset); + if (fd >= 0 && lseek(fd, offset, SEEK_SET) == offset) { + rc = qemuMonitorMigrateToFd(priv->mon, + QEMU_MONITOR_MIGRATE_BACKGROUND, + fd); + } else { + rc = qemuMonitorMigrateToFile(priv->mon, + QEMU_MONITOR_MIGRATE_BACKGROUND, + args, path, offset); + } + VIR_FORCE_CLOSE(fd); qemuDomainObjExitMonitorWithDriver(driver, vm); } else { const char *prog = qemudSaveCompressionTypeToString(header.compressed);