On Mon, 27 Aug 2012 09:36:05 +0200
Benoît Canet <benoit.ca...@irqsave.net> wrote:
> Adding Luiz to the thread since he is concerned by migration.
>
> Luiz do you have any hints on doing this properly ?
I don't. Juan is a better option though.
But, we use exec migration for this, no?
>
> Benoît
>
> > Le Thursday 23 Aug 2012 à 13:34:01 (+0100), Daniel P. Berrange a écrit :
> > On Thu, Aug 23, 2012 at 02:28:07PM +0200, Benoît Canet wrote:
> > > Usage:
> > > (qemu) migrate file:/path/to/vm_statefile
> > >
> > > Signed-off-by: Benoit Canet <ben...@irqsave.net>
> > > ---
> > > migration-fd.c | 4 ++--
> > > migration.c | 20 +++++++++++++++++++-
> > > migration.h | 2 +-
> > > 3 files changed, 22 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/migration-fd.c b/migration-fd.c
> > > index 50138ed..d39e44a 100644
> > > --- a/migration-fd.c
> > > +++ b/migration-fd.c
> > > @@ -73,9 +73,9 @@ static int fd_close(MigrationState *s)
> > > return 0;
> > > }
> > >
> > > -int fd_start_outgoing_migration(MigrationState *s, const char *fdname)
> > > +int fd_start_outgoing_migration(MigrationState *s, const char *fdname,
> > > int fd)
> > > {
> > > - s->fd = monitor_get_fd(cur_mon, fdname);
> > > + s->fd = fd ? fd : monitor_get_fd(cur_mon, fdname);
> > > if (s->fd == -1) {
> > > DPRINTF("fd_migration: invalid file descriptor identifier\n");
> > > goto err_after_get_fd;
> > > diff --git a/migration.c b/migration.c
> > > index 1edeec5..679847d 100644
> > > --- a/migration.c
> > > +++ b/migration.c
> > > @@ -239,9 +239,14 @@ void
> > > qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
> > > static int migrate_fd_cleanup(MigrationState *s)
> > > {
> > > int ret = 0;
> > > + struct stat st;
> > >
> > > qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
> > >
> > > + if (!fstat(s->fd, &st) && S_ISREG(st.st_mode)) {
> > > + fsync(s->fd);
> > > + }
> > > +
> > > if (s->file) {
> > > DPRINTF("closing file\n");
> > > ret = qemu_fclose(s->file);
> > > @@ -475,6 +480,17 @@ void migrate_del_blocker(Error *reason)
> > > migration_blockers = g_slist_remove(migration_blockers, reason);
> > > }
> > >
> > > +static int file_start_outgoing_migration(MigrationState *s,
> > > + const char *filename)
> > > +{
> > > + int fd;
> > > + fd = open(filename, O_CREAT|O_TRUNC|O_WRONLY, S_IRUSR|S_IWUSR);
> > > + if (fd < 0) {
> > > + return -errno;
> > > + }
> > > + return fd_start_outgoing_migration(s, NULL, fd);
> >
> > 'fd_start_outgoing_migration' requires that the FD you give it
> > supports non-blocking I/O. File descriptors opened from plain
> > files or block devices do not honour that requirement. So this
> > proposed code will cause the entire QEMU process to block while
> > migration is taking place. This is why no on has ever implemented
> > the 'file:' protocol in QEMU before.
> >
> > To deal with this issue you'd either have to use the POSIX
> > async I/O APIs (or QEMU's internal equivalent), or spawn a
> > separate 'dd' helper process and give QEMU a pipe FD instead.
> > The latter is what libvirt does to implement migrate to file.
> >
> > Daniel
> > --
> > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/
> > :|
> > |: http://libvirt.org -o- http://virt-manager.org
> > :|
> > |: http://autobuild.org -o- http://search.cpan.org/~danberr/
> > :|
> > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc
> > :|
> >
>
