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envelope-from=vsementsov@virtuozzo.com; helo=EUR04-VI1-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, 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" The logic around **child is not obvious: this reference is used not only to return resulting child, but also to rollback NULL value on transaction abort. Let's document this. Signed-off-by: Vladimir Sementsov-Ogievskiy --- block.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/block.c b/block.c index 3fc87fbf90..1f89be6f97 100644 --- a/block.c +++ b/block.c @@ -2773,6 +2773,12 @@ static TransactionActionDrv bdrv_attach_child_common_drv = { /* * Common part of attaching bdrv child to bs or to blk or to job + * + * Resulting new child is returned through @child. + * At start *@child must be NULL. + * @child is saved to a new entry of @tran, so that *@child could be reverted to + * NULL on abort(). So referenced variable must live at least until transaction + * end. */ static int bdrv_attach_child_common(BlockDriverState *child_bs, const char *child_name, @@ -2847,6 +2853,10 @@ static int bdrv_attach_child_common(BlockDriverState *child_bs, return 0; } +/* + * Variable referenced by @child must live at least until transaction end. + * (see bdrv_attach_child_common() doc for details) + */ static int bdrv_attach_child_noperm(BlockDriverState *parent_bs, BlockDriverState *child_bs, const char *child_name, -- 2.29.2