Am 09.08.2019 um 18:13 hat Max Reitz geschrieben:
> Use child access functions when iterating through backing chains so
> filters do not break the chain.
>
> Signed-off-by: Max Reitz <mre...@redhat.com>
> ---
> block.c | 40 ++++++++++++++++++++++++++++------------
> 1 file changed, 28 insertions(+), 12 deletions(-)
>
> diff --git a/block.c b/block.c
> index 86b84bea21..42abbaf0ba 100644
> --- a/block.c
> +++ b/block.c
> @@ -4376,7 +4376,8 @@ int bdrv_change_backing_file(BlockDriverState *bs,
> }
>
> /*
> - * Finds the image layer in the chain that has 'bs' as its backing file.
> + * Finds the image layer in the chain that has 'bs' (or a filter on
> + * top of it) as its backing file.
> *
> * active is the current topmost image.
> *
> @@ -4388,11 +4389,18 @@ int bdrv_change_backing_file(BlockDriverState *bs,
> BlockDriverState *bdrv_find_overlay(BlockDriverState *active,
> BlockDriverState *bs)
> {
> - while (active && bs != backing_bs(active)) {
> - active = backing_bs(active);
> + bs = bdrv_skip_rw_filters(bs);
> + active = bdrv_skip_rw_filters(active);
This does more than the commit message says. In addition to iterating
through filters instead of stopping, it also changes the semantics of
the function to return the next non-filter on top of bs instead of the
next node.
The block jobs seem to use it only for bdrv_is_allocated_above(), which
should return the same thing in both cases, so the behaviour stays the
same. qmp_block_commit() will check op blockers on a different node now,
which could be a fix or a bug, I can't tell offhand. Probably the
blocking doesn't really work anyway.
All of this should be mentioned in the commit message at least. Maybe
it's also worth splitting in two patches.
> + while (active) {
> + BlockDriverState *next = bdrv_backing_chain_next(active);
> + if (bs == next) {
> + return active;
> + }
> + active = next;
> }
>
> - return active;
> + return NULL;
> }
>
> /* Given a BDS, searches for the base layer. */
> @@ -4544,9 +4552,7 @@ int bdrv_drop_intermediate(BlockDriverState *top,
> BlockDriverState *base,
> * other intermediate nodes have been dropped.
> * If 'top' is an implicit node (e.g. "commit_top") we should skip
> * it because no one inherits from it. We use explicit_top for that. */
> - while (explicit_top && explicit_top->implicit) {
> - explicit_top = backing_bs(explicit_top);
> - }
> + explicit_top = bdrv_skip_implicit_filters(explicit_top);
> update_inherits_from = bdrv_inherits_from_recursive(base, explicit_top);
>
> /* success - we can delete the intermediate states, and link top->base */
> @@ -5014,7 +5020,7 @@ BlockDriverState *bdrv_lookup_bs(const char *device,
> bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base)
> {
> while (top && top != base) {
> - top = backing_bs(top);
> + top = bdrv_filtered_bs(top);
> }
>
> return top != NULL;
> @@ -5253,7 +5259,17 @@ BlockDriverState
> *bdrv_find_backing_image(BlockDriverState *bs,
>
> is_protocol = path_has_protocol(backing_file);
>
> - for (curr_bs = bs; curr_bs->backing; curr_bs = curr_bs->backing->bs) {
> + /*
> + * Being largely a legacy function, skip any filters here
> + * (because filters do not have normal filenames, so they cannot
> + * match anyway; and allowing json:{} filenames is a bit out of
> + * scope).
> + */
> + for (curr_bs = bdrv_skip_rw_filters(bs);
> + bdrv_filtered_cow_child(curr_bs) != NULL;
> + curr_bs = bdrv_backing_chain_next(curr_bs))
This could just use bs_below instead of recalculating the node if you
moved the declaration of bs_below to the function scope.
> + {
> + BlockDriverState *bs_below = bdrv_backing_chain_next(curr_bs);
>
> /* If either of the filename paths is actually a protocol, then
> * compare unmodified paths; otherwise make paths relative */
> @@ -5261,7 +5277,7 @@ BlockDriverState
> *bdrv_find_backing_image(BlockDriverState *bs,
> char *backing_file_full_ret;
>
> if (strcmp(backing_file, curr_bs->backing_file) == 0) {
> - retval = curr_bs->backing->bs;
> + retval = bs_below;
> break;
> }
> /* Also check against the full backing filename for the image */
> @@ -5271,7 +5287,7 @@ BlockDriverState
> *bdrv_find_backing_image(BlockDriverState *bs,
> bool equal = strcmp(backing_file, backing_file_full_ret) ==
> 0;
> g_free(backing_file_full_ret);
> if (equal) {
> - retval = curr_bs->backing->bs;
> + retval = bs_below;
> break;
> }
> }
> @@ -5297,7 +5313,7 @@ BlockDriverState
> *bdrv_find_backing_image(BlockDriverState *bs,
> g_free(filename_tmp);
>
> if (strcmp(backing_file_full, filename_full) == 0) {
> - retval = curr_bs->backing->bs;
> + retval = bs_below;
> break;
> }
> }
Kevin
