Re: [Qemu-devel] [PATCH V2 2/2] qcow2: cancel the modification on fail in qcow2_snapshot_create()

[Wenchao Xia]

于 2013-5-17 17:27, Stefan Hajnoczi 写道:
> On Fri, May 17, 2013 at 03:56:45PM +0800, Wenchao Xia wrote:
> > Signed-off-by: Wenchao Xia <address@hidden>
> > ---
> >   block/qcow2-snapshot.c |   17 ++++++++++++++---
> >   1 files changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
> > index 45da32d..033f705 100644
> > --- a/block/qcow2-snapshot.c
> > +++ b/block/qcow2-snapshot.c
> > @@ -367,7 +367,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> > QEMUSnapshotInfo *sn_info)
> >       ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,
> >                         s->l1_size * sizeof(uint64_t));
> >       if (ret < 0) {
> > -        goto fail;
> > +        goto dealloc_cluster;
> >       }
> >
> >       g_free(l1_table);
> > @@ -380,7 +380,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> > QEMUSnapshotInfo *sn_info)
> >        */
> >       ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 
> > 1);
> >       if (ret < 0) {
> > -        goto fail;
> > +        goto dealloc_cluster;
> >       }
> >
> >       /* Append the new snapshot to the snapshot list */
> > @@ -397,7 +397,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> > QEMUSnapshotInfo *sn_info)
> >       if (ret < 0) {
> >           g_free(s->snapshots);
> >           s->snapshots = old_snapshot_list;
> > -        goto fail;
> > +        goto restore_refcount;
> >       }
> >
> >       g_free(old_snapshot_list);
> > @@ -410,6 +410,17 @@ int qcow2_snapshot_create(BlockDriverState *bs, 
> > QEMUSnapshotInfo *sn_info)
> >   #endif
> >       return 0;
> >
> > +restore_refcount:
> > +    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,
> > +                                         s->l1_size, -1);
> > +    if (ret < 0) {
> > +        /* Nothing can be done none now, need image check later */
> > +        error_report("qcow2: Error in restoring refcount in snapshot");
> > +    }
> > +
> > +dealloc_cluster:
> > +    qcow2_free_clusters(bs, sn->l1_table_offset, sn->l1_size);
>
> sn->l1_size is in uint64_t units, not in bytes.
>
> Do you have test cases to exercise these code paths?  Use blkdebug to
> inject errors at the right point so that the error code path is taken.
  OK, I'll try it.

--
Best Regards

Wenchao Xia