diff options
| -rw-r--r-- | block.c | 38 | ||||
| -rw-r--r-- | include/block/block_int.h | 10 |
2 files changed, 48 insertions, 0 deletions
diff --git a/block.c b/block.c index 145d0baf5e..e2fefe5883 100644 --- a/block.c +++ b/block.c @@ -6234,6 +6234,44 @@ bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs, return false; } +/* + * This function checks whether the given @to_replace is allowed to be + * replaced by a node that always shows the same data as @bs. This is + * used for example to verify whether the mirror job can replace + * @to_replace by the target mirrored from @bs. + * To be replaceable, @bs and @to_replace may either be guaranteed to + * always show the same data (because they are only connected through + * filters), or some driver may allow replacing one of its children + * because it can guarantee that this child's data is not visible at + * all (for example, for dissenting quorum children that have no other + * parents). + */ +bool bdrv_recurse_can_replace(BlockDriverState *bs, + BlockDriverState *to_replace) +{ + if (!bs || !bs->drv) { + return false; + } + + if (bs == to_replace) { + return true; + } + + /* See what the driver can do */ + if (bs->drv->bdrv_recurse_can_replace) { + return bs->drv->bdrv_recurse_can_replace(bs, to_replace); + } + + /* For filters without an own implementation, we can recurse on our own */ + if (bs->drv->is_filter) { + BdrvChild *child = bs->file ?: bs->backing; + return bdrv_recurse_can_replace(child->bs, to_replace); + } + + /* Safe default */ + return false; +} + BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs, const char *node_name, Error **errp) { diff --git a/include/block/block_int.h b/include/block/block_int.h index 640fb82c78..eaefac210e 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -102,6 +102,13 @@ struct BlockDriver { */ bool (*bdrv_recurse_is_first_non_filter)(BlockDriverState *bs, BlockDriverState *candidate); + /* + * Return true if @to_replace can be replaced by a BDS with the + * same data as @bs without it affecting @bs's behavior (that is, + * without it being visible to @bs's parents). + */ + bool (*bdrv_recurse_can_replace)(BlockDriverState *bs, + BlockDriverState *to_replace); int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *filename); int (*bdrv_probe_device)(const char *filename); @@ -1263,6 +1270,9 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c, uint64_t perm, uint64_t shared, uint64_t *nperm, uint64_t *nshared); +bool bdrv_recurse_can_replace(BlockDriverState *bs, + BlockDriverState *to_replace); + /* * Default implementation for drivers to pass bdrv_co_block_status() to * their file. |