Backing files are somewhat special compared to other kinds of children because they are attached and detached using bdrv_set_backing_hd() rather than the normal set of functions, which does a few more things like setting backing blockers, toggling the BDRV_O_NO_BACKING flag, setting parent_bs->backing_file, etc.
These special features are a reason why change_parent_backing_link() can't handle backing files yet. With abstracting the additional features into .attach/.detach callbacks, we get a step closer to a function that can actually deal with this. Signed-off-by: Kevin Wolf <kw...@redhat.com> --- block.c | 94 +++++++++++++++++++++++++++++------------------ include/block/block_int.h | 3 ++ 2 files changed, 62 insertions(+), 35 deletions(-) diff --git a/block.c b/block.c index 1e01647..ff328f1 100644 --- a/block.c +++ b/block.c @@ -800,6 +800,57 @@ const BdrvChildRole child_format = { .drained_end = bdrv_child_cb_drained_end, }; +static void bdrv_backing_attach(BdrvChild *c) +{ + BlockDriverState *parent = c->opaque; + BlockDriverState *backing_hd = c->bs; + + assert(!parent->backing_blocker); + error_setg(&parent->backing_blocker, + "node is used as backing hd of '%s'", + bdrv_get_device_or_node_name(parent)); + + parent->open_flags &= ~BDRV_O_NO_BACKING; + pstrcpy(parent->backing_file, sizeof(parent->backing_file), + backing_hd->filename); + pstrcpy(parent->backing_format, sizeof(parent->backing_format), + backing_hd->drv ? backing_hd->drv->format_name : ""); + + bdrv_op_block_all(backing_hd, parent->backing_blocker); + /* Otherwise we won't be able to commit or stream */ + bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_COMMIT_TARGET, + parent->backing_blocker); + bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_STREAM, + parent->backing_blocker); + /* + * We do backup in 3 ways: + * 1. drive backup + * The target bs is new opened, and the source is top BDS + * 2. blockdev backup + * Both the source and the target are top BDSes. + * 3. internal backup(used for block replication) + * Both the source and the target are backing file + * + * In case 1 and 2, neither the source nor the target is the backing file. + * In case 3, we will block the top BDS, so there is only one block job + * for the top BDS and its backing chain. + */ + bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_BACKUP_SOURCE, + parent->backing_blocker); + bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_BACKUP_TARGET, + parent->backing_blocker); +} + +static void bdrv_backing_detach(BdrvChild *c) +{ + BlockDriverState *parent = c->opaque; + + assert(parent->backing_blocker); + bdrv_op_unblock_all(c->bs, parent->backing_blocker); + error_free(parent->backing_blocker); + parent->backing_blocker = NULL; +} + static char *bdrv_backing_link_name(BdrvChild *c) { BlockDriverState *parent = c->opaque; @@ -832,6 +883,8 @@ static void bdrv_backing_options(int *child_flags, QDict *child_options, } static const BdrvChildRole child_backing = { + .attach = bdrv_backing_attach, + .detach = bdrv_backing_detach, .get_link_name = bdrv_backing_link_name, .inherit_options = bdrv_backing_options, .drained_begin = bdrv_child_cb_drained_begin, @@ -1606,6 +1659,9 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs) if (old_bs->quiesce_counter && child->role->drained_end) { child->role->drained_end(child); } + if (child->role->detach) { + child->role->detach(child); + } QLIST_REMOVE(child, next_parent); bdrv_update_perm(old_bs); } @@ -1618,6 +1674,9 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs) child->role->drained_begin(child); } bdrv_update_perm(new_bs); + if (child->role->attach) { + child->role->attach(child); + } } } @@ -1758,52 +1817,17 @@ void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd) } if (bs->backing) { - assert(bs->backing_blocker); - bdrv_op_unblock_all(bs->backing->bs, bs->backing_blocker); bdrv_unref_child(bs, bs->backing); - } else if (backing_hd) { - error_setg(&bs->backing_blocker, - "node is used as backing hd of '%s'", - bdrv_get_device_or_node_name(bs)); } if (!backing_hd) { - error_free(bs->backing_blocker); - bs->backing_blocker = NULL; bs->backing = NULL; goto out; } /* FIXME Error handling */ bs->backing = bdrv_attach_child(bs, backing_hd, "backing", &child_backing, &error_abort); - bs->open_flags &= ~BDRV_O_NO_BACKING; - pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_hd->filename); - pstrcpy(bs->backing_format, sizeof(bs->backing_format), - backing_hd->drv ? backing_hd->drv->format_name : ""); - bdrv_op_block_all(backing_hd, bs->backing_blocker); - /* Otherwise we won't be able to commit or stream */ - bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_COMMIT_TARGET, - bs->backing_blocker); - bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_STREAM, - bs->backing_blocker); - /* - * We do backup in 3 ways: - * 1. drive backup - * The target bs is new opened, and the source is top BDS - * 2. blockdev backup - * Both the source and the target are top BDSes. - * 3. internal backup(used for block replication) - * Both the source and the target are backing file - * - * In case 1 and 2, neither the source nor the target is the backing file. - * In case 3, we will block the top BDS, so there is only one block job - * for the top BDS and its backing chain. - */ - bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_BACKUP_SOURCE, - bs->backing_blocker); - bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_BACKUP_TARGET, - bs->backing_blocker); out: bdrv_refresh_limits(bs, NULL); } diff --git a/include/block/block_int.h b/include/block/block_int.h index b24fc49..d37fcc2 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -456,6 +456,9 @@ struct BdrvChildRole { */ void (*drained_begin)(BdrvChild *child); void (*drained_end)(BdrvChild *child); + + void (*attach)(BdrvChild *child); + void (*detach)(BdrvChild *child); }; extern const BdrvChildRole child_file; -- 1.8.3.1