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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 AM6PR08MB4534.eurprd08.prod.outlook.com (2603:10a6:20b:ba::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3825.19; Fri, 5 Feb 2021 11:52:05 +0000 Received: from AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::f1f0:6610:11f5:5e4a]) by AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::f1f0:6610:11f5:5e4a%8]) with mapi id 15.20.3805.028; Fri, 5 Feb 2021 11:52:05 +0000 Subject: Re: [PATCH v7 08/14] block/qcow2: qcow2_get_specific_info(): drop error propagation To: Alberto Garcia , qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, armbru@redhat.com, eblake@redhat.com, jsnow@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, pavel.dovgaluk@ispras.ru, ari@tuxera.com, mreitz@redhat.com, kwolf@redhat.com References: <20210202124956.63146-1-vsementsov@virtuozzo.com> <20210202124956.63146-9-vsementsov@virtuozzo.com> From: Vladimir Sementsov-Ogievskiy Message-ID: Date: Fri, 5 Feb 2021 14:52:03 +0300 User-Agent: Mozilla/5.0 (X11; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR04-HE1-obe.outbound.protection.outlook.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 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=-0.33, 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" 05.02.2021 14:43, Alberto Garcia wrote: > On Tue 02 Feb 2021 01:49:50 PM CET, Vladimir Sementsov-Ogievskiy wrote: >> -Qcow2BitmapInfoList *qcow2_get_bitmap_info_list(BlockDriverState *bs, >> - Error **errp) >> +bool qcow2_get_bitmap_info_list(BlockDriverState *bs, >> + Qcow2BitmapInfoList **info_list, Error **errp) >> { >> BDRVQcow2State *s = bs->opaque; >> Qcow2BitmapList *bm_list; >> Qcow2Bitmap *bm; >> - Qcow2BitmapInfoList *list = NULL; >> - Qcow2BitmapInfoList **tail = &list; >> >> if (s->nb_bitmaps == 0) { >> - return NULL; >> + *info_list = NULL; >> + return true; >> } >> >> bm_list = bitmap_list_load(bs, s->bitmap_directory_offset, >> s->bitmap_directory_size, errp); >> - if (bm_list == NULL) { >> - return NULL; >> + if (!bm_list) { >> + return false; >> } >> >> + *info_list = NULL; >> + >> QSIMPLEQ_FOREACH(bm, bm_list, entry) { >> Qcow2BitmapInfo *info = g_new0(Qcow2BitmapInfo, 1); >> info->granularity = 1U << bm->granularity_bits; >> info->name = g_strdup(bm->name); >> info->flags = get_bitmap_info_flags(bm->flags & ~BME_RESERVED_FLAGS); >> - QAPI_LIST_APPEND(tail, info); >> + QAPI_LIST_APPEND(info_list, info); >> } >> >> bitmap_list_free(bm_list); >> >> - return list; >> + return true; >> } > > Maybe I'm reading this wrong but... > > In the original code you had the head and tail of the list ('list' and > 'tail') then you would append items to the tail and finally return the > head. > > However the new code only uses and updates 'info_list' and it does not > keep the head anywhere, so what the caller gets is a pointer to the > tail. > No. *info_list is modified only on the first loop iteration. And than info_list is switched to &(*(info_list))->next, so on second iteration we will modify @next field of first element, not original *info_list. -- Best regards, Vladimir