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client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 824C2C0669D5; Mon, 20 May 2019 16:43:13 +0000 (UTC) Received: from [10.18.17.162] (dhcp-17-162.bos.redhat.com [10.18.17.162]) by smtp.corp.redhat.com (Postfix) with ESMTP id 458F660E37; Mon, 20 May 2019 16:43:05 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , Kevin Wolf References: <20190514201926.10407-1-jsnow@redhat.com> <72986b5d-0772-abfb-2c99-97470e8fd3da@virtuozzo.com> <20190520092737.GA5699@localhost.localdomain> From: John Snow Openpgp: preference=signencrypt Autocrypt: addr=jsnow@redhat.com; prefer-encrypt=mutual; keydata= mQINBFTKefwBEAChvwqYC6saTzawbih87LqBYq0d5A8jXYXaiFMV/EvMSDqqY4EY6whXliNO IYzhgrPEe7ZmPxbCSe4iMykjhwMh5byIHDoPGDU+FsQty2KXuoxto+ZdrP9gymAgmyqdk3aV vzzmCa3cOppcqKvA0Kqr10UeX/z4OMVV390V+DVWUvzXpda45/Sxup57pk+hyY52wxxjIqef rj8u5BN93s5uCVTus0oiVA6W+iXYzTvVDStMFVqnTxSxlpZoH5RGKvmoWV3uutByQyBPHW2U 1Y6n6iEZ9MlP3hcDqlo0S8jeP03HaD4gOqCuqLceWF5+2WyHzNfylpNMFVi+Hp0H/nSDtCvQ 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List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Peter Maydell , aihua liang , "qemu-block@nongnu.org" , Juan Quintela , "qemu-devel@nongnu.org" , "Dr. David Alan Gilbert" , Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/20/19 6:37 AM, Vladimir Sementsov-Ogievskiy wrote: > 20.05.2019 12:27, Kevin Wolf wrote: >> Am 17.05.2019 um 12:22 hat Vladimir Sementsov-Ogievskiy geschrieben: >>> 16.05.2019 22:03, John Snow wrote: >>>> On 5/16/19 6:12 AM, Vladimir Sementsov-Ogievskiy wrote: >>>>> But, on the other, hand, if we have implicitly-filtered node on target, we were doing wrong thing anyway, >>>>> as dirty_bitmap_load_header don't skip implicit nodes. >>>>> >>>>>> + for (bs = bdrv_next_all_states(NULL); bs; bs = bdrv_next_all_states(bs)) { >>>>> >>>>> As I understand, difference with bdrv_next_node is that we don't skip unnamed nodes [...] >>>>> >>>> >>>> The difference is that we iterate over states that aren't roots of >>>> trees; so not just unnamed nodes but rather intermediate nodes as well >>>> as nodes not attached to a storage device. >>>> >>>> bdrv_next says: `Iterates over all top-level BlockDriverStates, i.e. >>>> BDSs that are owned by the monitor or attached to a BlockBackend` >>>> >>>> So this loop is going to iterate over *everything*, not just top-level >>>> nodes. This lets me skip the tree-crawling loop that didn't work quite >>>> right. >>> >>> I meant not bdrv_next but bdrv_next_node, which iterates through graph nodes.. >>> What is real difference between graph_bdrv_states and all_bdrv_states ? >> >> I don't think there is any relevant difference any more since commit >> 15489c769b9 ('block: auto-generated node-names'). We can only see a >> difference if a BDS was created, but never opened. This means either >> that we are still in the process of opening an image or that we have a >> bug somewhere. >> >> Maybe we should remove graph_bdrv_states and replace all of its uses >> with the more obviously correct all_bdrv_states (if we are sure that >> all users aren't called between creating and opening a BDS). >> >>> Node is inserted to graph_bdrv_states in bdrv_assign_node_name(), and to >>> all_bdrv_states in bdrv_new(). >>> >>> Three calls to bdrv_new: >>> >>> bdrv_new_open_driver, calls bdrv_new and then bdrv_open_driver, which calls bdrv_assign_node_name, >>> and if it fails new created node is released. >>> >>> bdrv_open_inherit >>> bdrv_new >>> .. >>> bdrv_open_common >>> bdrv_open_driver >>> bdrv_assign_node_name >>> >>> >>> iscsi_co_create_opts >>> bdrv_new >>> >>> ... hmm.. looks like it a kind of temporary unnamed bs >>> >>> So, now, I'm not sure. Possibly we'd better use bdrv_next_node(). >> >> I wonder if the iscsi one can't be replaced with bdrv_new_open_driver(). >> Manually building a half-opened BDS like it does currently looks >> suspicious. >> >>> Kevin introduced all_bdrv_states in 0f12264e7a4145 , to use in drain instead of >>> bdrv_next... But I don't understand, why he didn't use graph_bdrv_states and >>> corresponding bdrv_next_node(), which is only skips some temporary or under-constuction >>> nodes.. >> >> I probably just didn't realise that graph_bdrv_states exists and is >> effectively the same. I knew that all_bdrv_states contains what I want, >> so I just wanted to access that. >> >> But if anonymous BDSes did actually still exist, drain would want to >> wait for those as well, so it's the more natural choice anyway. >> >> Kevin >> > > Thank you for clarification. Then, my r-b still stand here, and fixing/refacting > graph_nodes vs all_states should be a separate thing. > > Reviewed-by: Vladimir Sementsov-Ogievskiy > Great, thanks all :) I think I will stage this through my tree -- on the premise that David Gilbert won't want to stage a block patch, and that since it's not Kevin's tree, he won't mind either. --js