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dkim=none (message not signed) header.d=none;redhat.com; dmarc=none action=none header.from=virtuozzo.com; Received: from AM7PR08MB5494.eurprd08.prod.outlook.com (2603:10a6:20b:dc::15) by AS8PR08MB5912.eurprd08.prod.outlook.com (2603:10a6:20b:29f::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4500.16; Thu, 16 Sep 2021 10:12:17 +0000 Received: from AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::2817:53b3:f8b4:fe22]) by AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::2817:53b3:f8b4:fe22%9]) with mapi id 15.20.4523.016; Thu, 16 Sep 2021 10:12:17 +0000 Subject: Re: [PATCH 2/8] block: add BlockParentClass class To: Markus Armbruster Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, ehabkost@redhat.com, berrange@redhat.com, pbonzini@redhat.com, eblake@redhat.com, mreitz@redhat.com, kwolf@redhat.com, den@openvz.org, nshirokovskiy@virtuozzo.com, yur@virtuozzo.com, dim@virtuozzo.com, igor@virtuozzo.com, pkrempa@redhat.com, libvir-list@redhat.com, stefanha@redhat.com References: <20210802185416.50877-1-vsementsov@virtuozzo.com> <20210802185416.50877-3-vsementsov@virtuozzo.com> <87h7ekapfw.fsf@dusky.pond.sub.org> From: Vladimir Sementsov-Ogievskiy Message-ID: Date: Thu, 16 Sep 2021 13:12:15 +0300 User-Agent: Mozilla/5.0 (X11; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR04-VI1-obe.outbound.protection.outlook.com X-Spam_score_int: -37 X-Spam_score: -3.8 X-Spam_bar: --- X-Spam_report: (-3.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, NICE_REPLY_A=-1.698, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 16.09.2021 11:34, Markus Armbruster wrote: > Vladimir Sementsov-Ogievskiy writes: > >> Add a class that will unify block parents for blockdev-replace >> functionality we are going to add. >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy >> --- >> 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 >> + * >> + * 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 >> + * >> + * 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