Re: [Qemu-devel] [PATCH V4 2/6] qcow2: add error message in qcow2_write_snapshots()

[Wenchao Xia]

> On 14.10.2013 23:52, Wenchao Xia wrote:
> > The function still returns int since qcow2_snapshot_delete() will
> > return the number.
> >
> > Signed-off-by: Wenchao Xia <address@hidden>
> > ---
> >   block/qcow2-snapshot.c |   48 ++++++++++++++++++++++++++++++++++++++++++------
> >   1 files changed, 42 insertions(+), 6 deletions(-)
> >
> > diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
> > index b373f9a..4bd494b 100644
> > --- a/block/qcow2-snapshot.c
> > +++ b/block/qcow2-snapshot.c
> > @@ -152,7 +152,7 @@ fail:
> >   }
> >
> >   /* add at the end of the file a new list of snapshots */
> > -static int qcow2_write_snapshots(BlockDriverState *bs)
> > +static int qcow2_write_snapshots(BlockDriverState *bs, Error **errp)
> >   {
> >       BDRVQcowState *s = bs->opaque;
> >       QCowSnapshot *sn;
> > @@ -183,10 +183,18 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
> >       offset = snapshots_offset;
> >       if (offset < 0) {
> >           ret = offset;
> > +        error_setg(errp,
> > +                   "Failed in allocation of cluster for snapshot list: "
> > +                   "%d (%s)",
> > +                   ret, strerror(-ret));
>
> Again, error_setg_errno() is your friend.
>
> >           goto fail;
> >       }
> >       ret = bdrv_flush(bs);
> >       if (ret < 0) {
> > +        error_setg(errp,
> > +                   "Failed in flush after snapshot list cluster allocation: "
> > +                   "%d (%s)",
> > +                   ret, strerror(-ret));
> >           goto fail;
> >       }
> >
> > @@ -194,6 +202,10 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
> >        * must indeed be completely free */
> >       ret = qcow2_pre_write_overlap_check(bs, 0, offset, snapshots_size);
> >       if (ret < 0) {
> > +        error_setg(errp,
> > +                   "Failed in overlap check for snapshot list cluster at %"
> > +                   PRIi64 " with size %d: %d (%s)",
> > +                   offset, snapshots_size, ret, strerror(-ret));
> >           goto fail;
> >       }
> >
> > @@ -227,24 +239,40 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
> >
> >           ret = bdrv_pwrite(bs->file, offset, &h, sizeof(h));
> >           if (ret < 0) {
> > +            error_setg(errp,
> > +                       "Failed in write of snapshot header at %"
> > +                       PRIi64 " with size %" PRIu64 ": %d (%s)",
> > +                       offset, sizeof(h), ret, strerror(-ret));
>
> Again, on 32 bit systems, sizeof(size_t) is generally 4 and not 8 (you
> may want to cast sizeof(h) to int and just use %d).

  Maybe caset as (int64_t)sizeof(h) to avoid possible incomplete value?

> >               goto fail;
> >           }
> >           offset += sizeof(h);
> >
> >           ret = bdrv_pwrite(bs->file, offset, &extra, sizeof(extra));
> >           if (ret < 0) {
> > +            error_setg(errp,
> > +                       "Failed in write of extra snapshot data at %"
> > +                       PRIi64 " with size %" PRIu64 ": %d (%s)",
> > +                       offset, sizeof(extra), ret, strerror(-ret));
>
> Same here.
>
> >               goto fail;
> >           }
> >           offset += sizeof(extra);
> >
> >           ret = bdrv_pwrite(bs->file, offset, sn->id_str, id_str_size);
> >           if (ret < 0) {
> > +            error_setg(errp,
> > +                       "Failed in write of snapshot id string at %"
> > +                       PRIi64 " with size %d: %d (%s)",
> > +                       offset, id_str_size, ret, strerror(-ret));
> >               goto fail;
> >           }
> >           offset += id_str_size;
> >
> >           ret = bdrv_pwrite(bs->file, offset, sn->name, name_size);
> >           if (ret < 0) {
> > +            error_setg(errp,
> > +                       "Failed in write of snapshot name string at %"
> > +                       PRIi64 " with size %d: %d (%s)",
> > +                       offset, name_size, ret, strerror(-ret));
> >               goto fail;
> >           }
> >           offset += name_size;
> > @@ -256,6 +284,9 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
> >        */
> >       ret = bdrv_flush(bs);
> >       if (ret < 0) {
> > +        error_setg(errp,
> > +                   "Failed in flush after snapshot list update: %d (%s)",
> > +                   ret, strerror(-ret));
> >           goto fail;
> >       }
> >
> > @@ -268,6 +299,11 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
> >       ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots),
> >                              &header_data, sizeof(header_data));
> >       if (ret < 0) {
> > +        error_setg(errp,
> > +                   "Failed in update of image header at %"
> > +                   PRIi64 " with size %" PRIu64 ":%d (%s)",
> > +                   offsetof(QCowHeader, nb_snapshots), sizeof(header_data),
> > +                   ret, strerror(-ret));
>
> And here (also applies to offsetof(), which returns size_t as well).
> Also, you forgot a space after the colon (although you should be using
> error_setg_errno() anyway).

  Will use error_setg_errno().


> Max
>
> >           goto fail;
> >       }
> >
> > @@ -283,6 +319,9 @@ fail:
> >           qcow2_free_clusters(bs, snapshots_offset, snapshots_size,
> >                               QCOW2_DISCARD_ALWAYS);
> >       }
> > +    if (errp) {
> > +        g_assert(error_is_set(errp));
> > +    }
> >       return ret;
> >   }
> >
> > @@ -446,10 +485,8 @@ void qcow2_snapshot_create(BlockDriverState *bs,
> >       s->snapshots = new_snapshot_list;
> >       s->snapshots[s->nb_snapshots++] = *sn;
> >
> > -    ret = qcow2_write_snapshots(bs);
> > +    ret = qcow2_write_snapshots(bs, errp);
> >       if (ret < 0) {
> > -        /* Following line will be replaced with more detailed error later */
> > -        error_setg(errp, "Failed in write of snapshot");
> >           g_free(s->snapshots);
> >           s->snapshots = old_snapshot_list;
> >           s->nb_snapshots--;
> > @@ -623,9 +660,8 @@ int qcow2_snapshot_delete(BlockDriverState *bs,
> >               s->snapshots + snapshot_index + 1,
> >               (s->nb_snapshots - snapshot_index - 1) * sizeof(sn));
> >       s->nb_snapshots--;
> > -    ret = qcow2_write_snapshots(bs);
> > +    ret = qcow2_write_snapshots(bs, errp);
> >       if (ret < 0) {
> > -        error_setg(errp, "Failed to remove snapshot from snapshot list");
> >           return ret;
> >       }