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Fri, 21 May 2021 17:49:41 +0000 From: Vladimir Sementsov-Ogievskiy To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, vsementsov@virtuozzo.com, jsnow@redhat.com, mreitz@redhat.com, kwolf@redhat.com Subject: [PATCH 2/6] block/copy-before-write: require BLK_PERM_WRITE_UNCHANGED for fleecing Date: Fri, 21 May 2021 20:49:21 +0300 Message-Id: <20210521174925.62781-3-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210521174925.62781-1-vsementsov@virtuozzo.com> References: <20210521174925.62781-1-vsementsov@virtuozzo.com> X-Originating-IP: [185.215.60.197] X-ClientProxiedBy: HE1PR09CA0083.eurprd09.prod.outlook.com (2603:10a6:7:3d::27) To AM7PR08MB5494.eurprd08.prod.outlook.com (2603:10a6:20b:dc::15) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from localhost.localdomain (185.215.60.197) by HE1PR09CA0083.eurprd09.prod.outlook.com (2603:10a6:7:3d::27) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4150.23 via Frontend Transport; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR03-AM5-obe.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, 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" Now block-copy detects fleecing scheme and do write-unchanged operations if detected. So, let's require appropriate permissions. Signed-off-by: Vladimir Sementsov-Ogievskiy --- block/copy-before-write.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/block/copy-before-write.c b/block/copy-before-write.c index 6ed5bce1f1..1b104545bd 100644 --- a/block/copy-before-write.c +++ b/block/copy-before-write.c @@ -113,6 +113,14 @@ static void cbw_refresh_filename(BlockDriverState *bs) bs->file->bs->filename); } +static bool cbw_is_fleecing(BlockDriverState *bs) +{ + BDRVCopyBeforeWriteState *s = bs->opaque; + + return bs->file && s->target && + bdrv_skip_filters(bs) == bdrv_backing_chain_next(s->target->bs); +} + static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c, BdrvChildRole role, BlockReopenQueue *reopen_queue, @@ -129,7 +137,8 @@ static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c, * only upfront. */ *nshared = BLK_PERM_ALL & ~BLK_PERM_RESIZE; - *nperm = BLK_PERM_WRITE; + *nperm = + cbw_is_fleecing(bs) ? BLK_PERM_WRITE_UNCHANGED : BLK_PERM_WRITE; } else { /* Source child */ bdrv_default_perms(bs, c, role, reopen_queue,