16.09.2021 11:34, Markus Armbruster wrote:
Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx> writes:Add a class that will unify block parents for blockdev-replace functionality we are going to add. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx> --- include/block/block-parent.h | 32 +++++++++++++++++ block/block-parent.c | 66 ++++++++++++++++++++++++++++++++++++ block/meson.build | 1 + 3 files changed, 99 insertions(+) create mode 100644 include/block/block-parent.h create mode 100644 block/block-parent.c diff --git a/include/block/block-parent.h b/include/block/block-parent.h new file mode 100644 index 0000000000..bd9c9d91e6 --- /dev/null +++ b/include/block/block-parent.h @@ -0,0 +1,32 @@ +/* + * Block Parent class + * + * Copyright (c) 2021 Virtuozzo International GmbH. + * + * Authors: + * Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#ifndef BLOCK_PARENT_H +#define BLOCK_PARENT_H + +#include "block/block.h" + +typedef struct BlockParentClass { + const char *name; + + int (*find_child)(const char *parent_id, const char *child_name, + BlockDriverState *child_bs, BdrvChild **child, + Error **errp);Callbacks should come with a contract.
will add
+ QTAILQ_ENTRY(BlockParentClass) next; +} BlockParentClass; + +void block_parent_class_register(BlockParentClass *cls); + +BdrvChild *block_find_child(const char *parent_id, const char *child_name, + BlockDriverState *child_bs, Error **errp); + +#endif /* BLOCK_PARENT_H */ diff --git a/block/block-parent.c b/block/block-parent.c new file mode 100644 index 0000000000..73b6026c42 --- /dev/null +++ b/block/block-parent.c @@ -0,0 +1,66 @@ +/* + * Block Parent class + * + * Copyright (c) 2021 Virtuozzo International GmbH. + * + * Authors: + * Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "block/block-parent.h" +#include "qapi/error.h" + +static QTAILQ_HEAD(, BlockParentClass) block_parent_classes = + QTAILQ_HEAD_INITIALIZER(block_parent_classes); + +void block_parent_class_register(BlockParentClass *cls) +{ + QTAILQ_INSERT_HEAD(&block_parent_classes, cls, next); +} + +BdrvChild *block_find_child(const char *parent_id, const char *child_name, + BlockDriverState *child_bs, Error **errp) +{ + BdrvChild *found_child = NULL; + BlockParentClass *found_cls = NULL, *cls; + + QTAILQ_FOREACH(cls, &block_parent_classes, next) { + int ret; + BdrvChild *c; + + /* + * Note that .find_child must fail if parent is found but doesn't have + * corresponding child. + */ + ret = cls->find_child(parent_id, child_name, child_bs, &c, errp); + if (ret < 0) { + return NULL; + } + if (ret == 0) { + continue; + } + + if (!found_child) { + found_cls = cls; + found_child = c; + continue; + } + + error_setg(errp, "{%s, %s} parent-child pair is ambiguous: it match " + "both %s and %s", parent_id, child_name, found_cls->name, + cls->name); + return NULL; + } + + if (!found_child) { + error_setg(errp, "{%s, %s} parent-child pair not found", parent_id, + child_name); + return NULL; + } + + return found_child; +}Especially when the callback can return NULL with and without setting an error!
Hmm. Callback returns int. And this block_find_child() function return NULL only together with errp set.
diff --git a/block/meson.build b/block/meson.build index 0450914c7a..5200e0ffce 100644 --- a/block/meson.build +++ b/block/meson.build @@ -10,6 +10,7 @@ block_ss.add(files( 'blkverify.c', 'block-backend.c', 'block-copy.c', + 'block-parent.c', 'commit.c', 'copy-on-read.c', 'preallocate.c',
-- Best regards, Vladimir
