Re: [Qemu-block] [PATCH 15/21] qcow2: add .bdrv_can_store_dirty_bitmap

[Vladimir Sementsov-Ogievskiy]

09.12.2016 20:28, Max Reitz wrote:
> On 22.11.2016 18:26, Vladimir Sementsov-Ogievskiy wrote:
> > Realize .bdrv_can_store_dirty_bitmap interface.
> >
> > Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> > ---
> >   block/qcow2-bitmap.c | 40 ++++++++++++++++++++++++++++++++++++++++
> >   block/qcow2.c        |  1 +
> >   block/qcow2.h        |  4 ++++
> >   3 files changed, 45 insertions(+)
> >
> > diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
> > index a975388..55b1112 100644
> > --- a/block/qcow2-bitmap.c
> > +++ b/block/qcow2-bitmap.c
> > @@ -1115,3 +1115,43 @@ fail:
> >   
> >       bitmap_list_free(bm_list);
> >   }
> > +
> > +bool qcow2_can_store_dirty_bitmap(BlockDriverState *bs,
> > +                                  const char *name,
> > +                                  uint32_t granularity,
> > +                                  Error **errp)
> > +{
> > +    BDRVQcow2State *s = bs->opaque;
> > +    const char *reason = NULL;
> > +    bool found;
> > +    Qcow2BitmapList *bm_list;
> > +
> > +    if (check_constraints_on_bitmap(bs, name, granularity) != 0) {
> > +        reason = "it doesn't satisfy the constraints";
> > +        goto common_errp;
> > +    }
> > +
> > +    if (s->nb_bitmaps == 0) {
> > +        return true;
> > +    }
> > +
> > +    bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
> > +                               s->bitmap_directory_size, errp);
> Maybe it would make sense to keep the bitmap list in memory...
>
> > +    if (bm_list == NULL) {
> > +        return false;
> > +    }
> > +
> > +    found = !!find_bitmap_by_name(bm_list, name);
> You can omit the !!, storing it in a bool will do that for you.
>
> > +    bitmap_list_free(bm_list);
> > +    if (found) {
> > +        reason = "bitmap with the same name is already stored";
> > +        goto common_errp;
> > +    }
> > +
> > +    return true;
> > +
> > +common_errp:
> > +    error_setg(errp, "Can't make bitmap '%s' persistent in '%s', as %s.",
> > +               name, bdrv_get_device_or_node_name(bs), reason);
> Hm, so this function isn't for checking whether a bitmap can be stored,
> but whether it can be made persistent. That's a difference; you can
> store a bitmap of the same name in the file if you want to overwrite it
> (i.e. it's an auto-load bitmap), but you cannot create a new bitmap with
> the same name.
>
> Maybe rename it from bdrv_can_store_dirty_bitmap to
> bdrv_can_store_new_dirty_bitmap?

Yes, I'll rename it.

> Max
>
> > +    return false;
> > +}
> > diff --git a/block/qcow2.c b/block/qcow2.c
> > index 66c7f74..cb9c2a2 100644
> > --- a/block/qcow2.c
> > +++ b/block/qcow2.c
> > @@ -3516,6 +3516,7 @@ BlockDriver bdrv_qcow2 = {
> >   
> >       .bdrv_load_autoloading_dirty_bitmaps = qcow2_load_autoloading_dirty_bitmaps,
> >       .bdrv_store_persistent_dirty_bitmaps = 
> > qcow2_store_persistent_dirty_bitmaps,
> > +    .bdrv_can_store_dirty_bitmap = qcow2_can_store_dirty_bitmap,
> >   };
> >   
> >   static void bdrv_qcow2_init(void)
> > diff --git a/block/qcow2.h b/block/qcow2.h
> > index d9a7643..e7a44a1 100644
> > --- a/block/qcow2.h
> > +++ b/block/qcow2.h
> > @@ -616,5 +616,9 @@ void qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, 
> > void **table);
> >   /* qcow2-bitmap.c functions */
> >   void qcow2_load_autoloading_dirty_bitmaps(BlockDriverState *bs, Error **errp);
> >   void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp);
> > +bool qcow2_can_store_dirty_bitmap(BlockDriverState *bs,
> > +                                  const char *name,
> > +                                  uint32_t granularity,
> > +                                  Error **errp);
> >   
> >   #endif


--
Best regards,
Vladimir