On Tue, 07/02 12:16, Paolo Bonzini wrote:
> Il 02/07/2013 07:59, Fam Zheng ha scritto:
> > Previously, nbd call drive_get_ref on the drive of bs. A BDS doesn't
> > always have associated dinfo, it's more proper to use bdrv_get_ref().
>
> This has the important side effect of marking the exported disk as
> "in_use" (to use the terms before the series). Right now you can serve
> a disk and, at the same time, stream it or mirror it or create a live
> snapshot of it.
>
> Do we really want to block anything for a device being served? Perhaps
> truncation, but maybe not even that. The NBD server is meant to be as
> unobtrusive as possible (in some sense NBD accesses are the same as
> guest accesses).
>
> Paolo
>
OK, it is better to work like that. But I don't quite understand why was
there drive_get_ref() on the device (w/o the series), as there's already
a close notifier? And it just drive_put_ref() when bs is closed?
> > Signed-off-by: Fam Zheng <f...@redhat.com>
> > ---
> > blockdev-nbd.c | 9 +--------
> > nbd.c | 5 +++++
> > 2 files changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/blockdev-nbd.c b/blockdev-nbd.c
> > index 95f10c8..d8bcd6f 100644
> > --- a/blockdev-nbd.c
> > +++ b/blockdev-nbd.c
> > @@ -69,12 +69,6 @@ static void nbd_close_notifier(Notifier *n, void *data)
> > g_free(cn);
> > }
> >
> > -static void nbd_server_put_ref(NBDExport *exp)
> > -{
> > - BlockDriverState *bs = nbd_export_get_blockdev(exp);
> > - drive_put_ref(drive_get_by_blockdev(bs));
> > -}
> > -
> > void qmp_nbd_server_add(const char *device, bool has_writable, bool
> > writable,
> > Error **errp)
> > {
> > @@ -106,10 +100,9 @@ void qmp_nbd_server_add(const char *device, bool
> > has_writable, bool writable,
> > }
> >
> > exp = nbd_export_new(bs, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY,
> > - nbd_server_put_ref);
> > + NULL);
> >
> > nbd_export_set_name(exp, device);
> > - drive_get_ref(drive_get_by_blockdev(bs));
> >
> > n = g_malloc0(sizeof(NBDCloseNotifier));
> > n->n.notify = nbd_close_notifier;
> > diff --git a/nbd.c b/nbd.c
> > index 2606403..f28b9fb 100644
> > --- a/nbd.c
> > +++ b/nbd.c
> > @@ -881,6 +881,7 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t
> > dev_offset,
> > exp->nbdflags = nbdflags;
> > exp->size = size == -1 ? bdrv_getlength(bs) : size;
> > exp->close = close;
> > + bdrv_get_ref(bs);
> > return exp;
> > }
> >
> > @@ -927,6 +928,10 @@ void nbd_export_close(NBDExport *exp)
> > }
> > nbd_export_set_name(exp, NULL);
> > nbd_export_put(exp);
> > + if (exp->bs) {
> > + bdrv_put_ref(exp->bs);
> > + exp->bs = NULL;
> > + }
> > }
> >
> > void nbd_export_get(NBDExport *exp)
> >
>
--
Fam
