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

On Wed, Mar 09, 2011 at 06:45:46PM -0700, Eric Blake wrote: > 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(-) > > + /* 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); Ok, so this is the bit which causes a regression on NFS rootsquash, if the path isn't readable by root.

> 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);