06.06.2019 21:41, John Snow wrote:
> When we check to see if we can store a bitmap, we don't check how many
> we've queued up. This can cause a problem saving bitmaps on close
> instead of when we request them to be added. With the stricter add
> interface, prohibit these bitmaps specifically.
>
> To match, make the remove interface more strict as well; now rejecting
> any requests to remove bitmaps that were never queued for storage.
>
> We don't need to "find" the bitmap when the interface has been given the
> bitmap explicitly, but this is done to make sure that the bitmap given
> actually does belong to the bs we were passed as a paranoia check to
> enforce consistency.
If you want to check it, I'd really prefer to do it explictly,
by adding "bool bdrv_has_dirty_bitmap(bs, bitmap) handler, or bitmap.bs field",
instead of hiding it under inconvenient interface of helper, so we actually do
name = bdrv_dirty_bitmap_name(bitmap);
bitmap = bdrv_find_dirty_bitmap(bs, name);
it really looks strange.
Hmmm, when I read series cover letter and this commit message, I thought
that you'll just calculate current number of persistent bitmaps on bs..
Do we really need to introduce additional counters on qcow2 state?
So, you want to check nb_queued + s->nb_bitmaps instead of just s->nb_bitmaps.
I think we can just count persistent dirty bitmaps and take that number
(as, there should not be in-image bitmaps, for which we don't have in-ram
version, but we can check it too and return an error on mismatch (or count
in-image-not-in-ram bitmaps and this count to number of in-ram persistent
bitmaps it seems an extra thing)..
>
> ---
>
> "What about directory size?" Please see the following patch.
>
> Signed-off-by: John Snow <js...@redhat.com>
> ---
> block/qcow2.h | 1 +
> block/dirty-bitmap.c | 8 +++-----
> block/qcow2-bitmap.c | 31 ++++++++++++++++++++++++++-----
> 3 files changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/block/qcow2.h b/block/qcow2.h
> index ce07f003f7..ebf60ac236 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -317,6 +317,7 @@ typedef struct BDRVQcow2State {
> QCowSnapshot *snapshots;
>
> uint32_t nb_bitmaps;
> + uint32_t nb_queued_bitmaps;
> uint64_t bitmap_directory_size;
> uint64_t bitmap_directory_offset;
>
> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> index 4667f9e65a..084c42af57 100644
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c
> @@ -450,11 +450,9 @@ void bdrv_release_named_dirty_bitmaps(BlockDriverState
> *bs)
> }
>
> /**
> - * Remove persistent dirty bitmap from the storage if it exists.
> - * Absence of bitmap is not an error, because we have the following scenario:
> - * BdrvDirtyBitmap can have .persistent = true but not yet saved and have no
> - * stored version. For such bitmap bdrv_remove_persistent_dirty_bitmap()
> should
> - * not fail.
> + * Remove a persistent dirty bitmap from storage,
> + * or dequeue it from being stored if it is enqueued.
> + *
> * This function doesn't release the corresponding BdrvDirtyBitmap.
> */
> int bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
> index 930a6c91ff..7193c66787 100644
> --- a/block/qcow2-bitmap.c
> +++ b/block/qcow2-bitmap.c
> @@ -1402,6 +1402,23 @@ static Qcow2Bitmap
> *find_bitmap_by_name(Qcow2BitmapList *bm_list,
> return NULL;
> }
>
> +static int qcow2_remove_queued_dirty_bitmap(
> + BlockDriverState *bs, const char *name, Error **errp)
> +{
> + BDRVQcow2State *s = bs->opaque;
> + BdrvDirtyBitmap *bitmap = bdrv_find_dirty_bitmap(bs, name);
> + if (!bitmap) {
> + error_setg(errp, "Node '%s' has no stored or enqueued bitmap '%s'",
> + bdrv_get_node_name(bs), name);
> + return -ENOENT;
> + }
> + assert(s->nb_queued_bitmaps > 0);
> + assert(bdrv_dirty_bitmap_get_persistence(bitmap));
> + s->nb_queued_bitmaps -= 1;
> +
> + return 0;
> +}
> +
> int qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
> BdrvDirtyBitmap *bitmap,
> Error **errp)
> @@ -1413,9 +1430,7 @@ int
> qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
> const char *name = bdrv_dirty_bitmap_name(bitmap);
>
> if (s->nb_bitmaps == 0) {
> - /* Absence of the bitmap is not an error: see explanation above
> - * bdrv_remove_persistent_dirty_bitmap() definition. */
> - return 0;
> + return qcow2_remove_queued_dirty_bitmap(bs, name, errp);
> }
>
> if ((ret = bitmap_list_load(bs, &bm_list, errp))) {
> @@ -1424,6 +1439,7 @@ int
> qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>
> bm = find_bitmap_by_name(bm_list, name);
> if (bm == NULL) {
> + ret = qcow2_remove_queued_dirty_bitmap(bs, name, errp);
> goto fail;
> }
>
> @@ -1544,6 +1560,7 @@ void
> qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp)
> error_setg_errno(errp, -ret, "Failed to update bitmap extension");
> goto fail;
> }
> + s->nb_queued_bitmaps = 0;
>
> /* Bitmap directory was successfully updated, so, old data can be
> dropped.
> * TODO it is better to reuse these clusters */
> @@ -1618,6 +1635,7 @@ int qcow2_add_persistent_dirty_bitmap(BlockDriverState
> *bs,
> Qcow2BitmapList *bm_list;
> const char *name = bdrv_dirty_bitmap_name(bitmap);
> uint32_t granularity = bdrv_dirty_bitmap_granularity(bitmap);
> + uint32_t nb_bitmaps;
> int ret = 0;
>
> if (s->qcow_version < 3) {
> @@ -1636,11 +1654,12 @@ int
> qcow2_add_persistent_dirty_bitmap(BlockDriverState *bs,
> goto fail;
> }
>
> - if (s->nb_bitmaps == 0) {
> + nb_bitmaps = s->nb_bitmaps + s->nb_queued_bitmaps;
> + if (nb_bitmaps == 0) {
> return 0;
> }
>
> - if (s->nb_bitmaps >= QCOW2_MAX_BITMAPS) {
> + if (nb_bitmaps >= QCOW2_MAX_BITMAPS) {
> error_setg(errp,
> "Maximum number of persistent bitmaps is already
> reached");
> ret = -EOVERFLOW;
> @@ -1667,6 +1686,8 @@ int qcow2_add_persistent_dirty_bitmap(BlockDriverState
> *bs,
> goto fail;
> }
>
> + s->nb_queued_bitmaps += 1;
> +
> return 0;
> fail:
> error_prepend(errp, "Can't make bitmap '%s' persistent in '%s': ",
>
--
Best regards,
Vladimir
