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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 AM7PR08MB5334.eurprd08.prod.outlook.com (2603:10a6:20b:10b::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4065.20; Mon, 26 Apr 2021 17:18:53 +0000 Received: from AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::b403:c1a9:6bb7:133]) by AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::b403:c1a9:6bb7:133%7]) with mapi id 15.20.4065.027; Mon, 26 Apr 2021 17:18:53 +0000 Subject: Re: [PATCH v3 22/36] block: add bdrv_remove_filter_or_cow transaction action To: Kevin Wolf Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, armbru@redhat.com, fam@euphon.net, stefanha@redhat.com, jsnow@redhat.com, mreitz@redhat.com References: <20210317143529.615584-1-vsementsov@virtuozzo.com> <20210317143529.615584-23-vsementsov@virtuozzo.com> From: Vladimir Sementsov-Ogievskiy Message-ID: Date: Mon, 26 Apr 2021 20:18:48 +0300 User-Agent: Mozilla/5.0 (X11; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR05-DB8-obe.outbound.protection.outlook.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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=-0.001, RCVD_IN_DNSWL_LOW=-0.7, 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" 26.04.2021 19:26, Kevin Wolf wrote: > Am 17.03.2021 um 15:35 hat Vladimir Sementsov-Ogievskiy geschrieben: >> Signed-off-by: Vladimir Sementsov-Ogievskiy >> --- >> block.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-- >> 1 file changed, 76 insertions(+), 2 deletions(-) >> >> diff --git a/block.c b/block.c >> index 11f7ad0818..2fca1f2ad5 100644 >> --- a/block.c >> +++ b/block.c >> @@ -2929,12 +2929,19 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs) >> } >> } >> >> +static void bdrv_child_free(void *opaque) >> +{ >> + BdrvChild *c = opaque; >> + >> + g_free(c->name); >> + g_free(c); >> +} >> + >> static void bdrv_remove_empty_child(BdrvChild *child) >> { >> assert(!child->bs); >> QLIST_SAFE_REMOVE(child, next); >> - g_free(child->name); >> - g_free(child); >> + bdrv_child_free(child); >> } >> >> typedef struct BdrvAttachChildCommonState { >> @@ -4956,6 +4963,73 @@ static bool should_update_child(BdrvChild *c, BlockDriverState *to) >> return ret; >> } >> >> +typedef struct BdrvRemoveFilterOrCowChild { >> + BdrvChild *child; >> + bool is_backing; >> +} BdrvRemoveFilterOrCowChild; >> + >> +/* this doesn't restore original child bs, only the child itself */ > > Hm, this comment tells me that it's intentional, but why is it correct? that's because bdrv_remove_filter_or_cow_child_abort() aborts only part of bdrv_remove_filter_or_cow_child(). Look: bdrv_remove_filter_or_cow_child() firstly do bdrv_replace_child_safe(child, NULL, tran);, so bs would be restored by .abort() of bdrv_replace_child_safe() action. So, improved comment may look like: This doesn't restore original child bs, only the child itself. The bs would be restored by .abort() bdrv_replace_child_safe() subation of bdrv_remove_filter_or_cow_child() action. Probably it would be more correct to rename BdrvRemoveFilterOrCowChild -> BdrvRemoveFilterOrCowChildNoBs bdrv_remove_filter_or_cow_child_abort -> bdrv_remove_filter_or_cow_child_no_bs_abort bdrv_remove_filter_or_cow_child_commit -> bdrv_remove_filter_or_cow_child_no_bs_commit and assert on .abort() and .commit() that s->child->bs is NULL. > >> +static void bdrv_remove_filter_or_cow_child_abort(void *opaque) >> +{ >> + BdrvRemoveFilterOrCowChild *s = opaque; >> + BlockDriverState *parent_bs = s->child->opaque; >> + >> + QLIST_INSERT_HEAD(&parent_bs->children, s->child, next); >> + if (s->is_backing) { >> + parent_bs->backing = s->child; >> + } else { >> + parent_bs->file = s->child; >> + } >> +} > > Kevin > -- Best regards, Vladimir