From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1FE1C7618F for ; Tue, 16 Jul 2019 00:13:37 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8EF872080A for ; Tue, 16 Jul 2019 00:13:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8EF872080A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:44560 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hnB68-0002eM-QC for qemu-devel@archiver.kernel.org; Mon, 15 Jul 2019 20:13:36 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47305) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hnB5y-0002F2-Em for qemu-devel@nongnu.org; Mon, 15 Jul 2019 20:13:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hnB5x-00028i-8g for qemu-devel@nongnu.org; Mon, 15 Jul 2019 20:13:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55360) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hnB5t-000205-HU; Mon, 15 Jul 2019 20:13:22 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3607630820EA; Tue, 16 Jul 2019 00:13:17 +0000 (UTC) Received: from [10.18.17.130] (dhcp-17-130.bos.redhat.com [10.18.17.130]) by smtp.corp.redhat.com (Postfix) with ESMTP id C71E95C26B; Tue, 16 Jul 2019 00:13:13 +0000 (UTC) To: Markus Armbruster References: <20190530143941.241963-1-vsementsov@virtuozzo.com> <2a9f6327-1cb6-78eb-ad10-93a33c6e754c@redhat.com> <87a7ew9p3o.fsf@dusky.pond.sub.org> 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 ua7j+6Pt7q5rvqgHvRipkDDVsjqwasuNc3wyoHexrBeLU/iJBuDld5iLy+dHXoYMB3HmjMxj 3K5/8XhGrDx6BDFeO3HIpi3u2z1jniB7RtyVEtdupED6lqsDj0oSz9NxaOFZrS3Jf6z/kHIf h42mM9Sx7+s4c07N2LieUxcfqhFTaa/voRibF4cmkBVUhOD1AKXNfhEsTvmcz9NbUchCkcvA T9119CrsxfVsE7bXiGvdXnzyGLXdsoosjzwacKdOrVaDmN3Uy+SHiQXo6TlkSdV0XH2PUxTM LsBFIO9qXO43Ai6J6iPAP/01l8fuZfpJE0/L/c25yyaND7xA3wARAQABtCpKb2huIFNub3cg KEpvaG4gSHVzdG9uKSA8anNub3dAcmVkaGF0LmNvbT6JAlQEEwECAD4CGwMCHgECF4AFCwkI BwMFFQoJCAsFFgIDAQAWIQT665cRoSz0dYEvGPKIqQZNGDVh6wUCXF392gUJC1Xq3gAKCRCI qQZNGDVh6558D/9pM4pu4njX5aT6uUW3vAmbWLF1jfPxiTQgSHAnm9EBMZED/fsvkzj97clo LN7JKmbYZNgJmR01A7flG45V4iOR/249qAfaVuD+ZzZi1R4jFzr13WS+IEdn0hYp9ITndb7R ezW+HGu6/rP2PnfmDnNowgJu6Dp6IUEabq8SXXwGHXZPuMIrsXJxUdKJdGnh1o2u7271yNO7 J9PEMuMDsgjsdnaGtv7aQ9CECtXvBleAc06pLW2HU10r5wQyBMZGITemJdBhhdzGmbHAL0M6 vKi/bafHRWqfMqOAdDkv3Jg4arl2NCG/uNateR1z5e529+UlB4XVAQT+f5T/YyI65DFTY940 il3aZhA8u788jZEPMXmt94u7uPZbEYp7V0jt68SrTaOgO7NaXsboXFjwEa42Ug5lB5d5/Qdp 1AITUv0NJ51kKwhHL1dEagGeloIsGVQILmpS0MLdtitBHqZLsnJkRvtMaxo47giyBlv2ewmq tIGTlVLxHx9xkc9aVepOuiGlZaZB72c9AvZs9rKaAjgU2UfJHlB/Hr4uSk/1EY0IgMv4vnsG 1sA5gvS7A4T4euu0PqHtn2sZEWDrk5RDbw0yIb53JYdXboLFmFXKzVASfKh2ZVeXRBlQQSJi 3PBR1GzzqORlfryby7mkY857xzCI2NkIkD2eq+HhzFTfFOTdGrkCDQRUynn8ARAAwbhP45BE d/zAMBPV2dk2WwIwKRSKULElP3kXpcuiDWYQob3UODUUqClO+3aXVRndaNmZX9WbzGYexVo3 5j+CVBCGr3DlU8AL9pp3KQ3SJihWcDed1LSmUf8tS+10d6mdGxDqgnd/OWU214isvhgWZtZG MM/Xj7cx5pERIiP+jqu7PT1cibcfcEKhPjYdyV1QnLtKNGrTg/UMKaL+qkWBUI/8uBoa0HLs NH63bXsRtNAG8w6qG7iiueYZUIXKc4IHINUguqYQJVdSe+u8b2N5XNhDSEUhdlqFYraJvX6d TjxMTW5lzVG2KjztfErRNSUmu2gezbw1/CV0ztniOKDA7mkQi6UIUDRh4LxRm5mflfKiCyDQ L6P/jxHBxFv+sIgjuLrfNhIC1p3z9rvCh+idAVJgtHtYl8p6GAVrF+4xQV2zZH45tgmHo2+S JsLPjXZtWVsWANpepXnesyabWtNAV4qQB7/SfC77zZwsVX0OOY2Qc+iohmXo8U7DgXVDgl/R /5Qgfnlv0/3rOdMt6ZPy5LJr8D9LJmcP0RvX98jyoBOf06Q9QtEwJsNLCOCo2LKNL71DNjZr nXEwjUH66CXiRXDbDKprt71BiSTitkFhGGU88XCtrp8R9yArXPf4MN+wNYBjfT7K29gWTzxt 9DYQIvEf69oZD5Z5qHYGp031E90AEQEAAYkCPAQYAQIAJgIbDBYhBPrrlxGhLPR1gS8Y8oip Bk0YNWHrBQJcXf3JBQkLVerNAAoJEIipBk0YNWHrU1AP/1FOK2SBGbyhHa5vDHuf47fgLipC e0/h1E0vdSonzlhPxuZoQ47FjzG9uOhqqQG6/PqtWs/FJIyz8aGG4aV+pSA/9Ko3/2ND8MSY ZflWs7Y8Peg08Ro01GTHFITjEUgHpTpHiT6TNcZB5aZNJ8jqCtW5UlqvXXbVeSTmO70ZiVtc vUJbpvSxYmzhFfZWaXIPcNcKWL1rnmnzs67lDhMLdkYVf91aml/XtyMUlfB8Iaejzud9Ht3r C0pA9MG57pLblX7okEshxAC0+tUdY2vANWFeX0mgqRt1GSuG9XM9H/cKP1czfUV/FgaWo/Ya fM4eMhUAlL/y+/AJxxumPhBXftM4yuiktp2JMezoIMJI9fmhjfWDw7+2jVrx9ze1joLakFD1 rVAoHxVJ7ORfQ4Ni/qWbQm3T6qQkSMt4N/scNsMczibdTPxU7qtwQwIeFOOc3wEwmJ9Qe3ox TODQ0agXiWVj0OXYCHJ6MxTDswtyTGQW+nUHpKBgHGwUaR6d1kr/LK9+5LpOfRlK9VRfEu7D PGNiRkr8Abp8jHsrBqQWfUS1bAf62bq6XUel0kUCtb7qCq024aOczXYWPFpJFX+nhp4d7NeH Edq+wlC13sBSiSHC7T5yssJ+7JPa2ATLlSKhEvBsLe2TsSTTtFlA0nBclqhfJXzimiuge9qU E40lvMWBuQINBFTKimUBEADDbJ+pQ5M4QBMWkaWImRj7c598xIZ37oKM6rGaSnuB1SVb7YCr Ci2MTwQcrQscA2jm80O8VFqWk+/XsEp62dty47GVwSfdGje/3zv3VTH2KhOCKOq3oPP5ZXWY rz2d2WnTvx++o6lU7HLHDEC3NGLYNLkL1lyVxLhnhvcMxkf1EGA1DboEcMgnJrNB1pGP27ww cSfvdyPGseV+qZZa8kuViDga1oxmnYDxFKMGLxrClqHrRt8geQL1Wj5KFM5hFtGTK4da5lPn wGNd6/CINMeCT2AWZY5ySz7/tSZe5F22vPvVZGoPgQicYWdNc3ap7+7IKP86JNjmec/9RJcz jvrYjJdiqBVldXou72CtDydKVLVSKv8c2wBDJghYZitfYIaL8cTvQfUHRYTfo0n5KKSec8Vo vjDuxmdbOUBA+SkRxqmneP5OxGoZ92VusrwWCjry8HRsNdR+2T+ClDCO6Wpihu4V3CPkQwTy eCuMHPAT0ka5paTwLrnZIxsdfnjUa96T10vzmQgAxpbbiaLvgKJ8+76OPdDnhddyxd2ldYfw RkF5PEGg3mqZnYKNNBtwjvX49SAvgETQvLzQ8IKVgZS0m4z9qHHvtc1BsQnFfe+LJOFjzZr7 CrDNJMqk1JTHYsSi2JcN3vY32WMezXSQ0TzeMK4kdnclSQyp/h23GWod5QARAQABiQRbBBgB AgAmAhsCFiEE+uuXEaEs9HWBLxjyiKkGTRg1YesFAlxd/coFCQtV2mQCKcFdIAQZAQIABgUC VMqKZQAKCRB974EGqvw5DiJoEACLmuiRq9ifvOh5DyBFwRS7gvA14DsGQngmC57EzV0EFcfM XVi1jX5OtwUyUe0Az5r6lHyyHDsDsIpLKBlWrYCeLpUhRR3oy181T7UNxvujGFeTkzvLAOo6 Hs3b8Wv9ARg+7acRYkQRNY7k0GIJ6YZz149tRyRKAy/vSjsaB9Lt0NOd1wf2EQMKwRVELwJD y0AazGn+0PRP7Bua2YbtxaBmhBBDb2tPpwn8U9xdckB4Vlft9lcWNsC/18Gi9bpjd9FSbdH/ sOUI+3ToWYENeoT4IP09wn6EkgWaJS3nAUN/MOycNej2i4Yhy2wDDSKyTAnVkSSSoXk+tK91 HfqtokbDanB8daP+K5LgoiWHzjfWzsxA2jKisI4YCGjrYQzTyGOT6P6u6SEeoEx10865B/zc 8/vN50kncdjYz2naacIDEKQNZlnGLsGkpCbfmfdi3Zg4vuWKNdWr0wGUzDUcpqW0y/lUXna+ 6uyQShX5e4JD2UPuf9WAQ9HtgSAkaDd4O1I2J41sleePzZOVB3DmYgy+ECRJJ5nw3ihdxpgc y/v3lfcJaqiyCv0PF+K/gSOvwhH7CbVqARmptT7yhhxqFdaYWo2Z2ksuKyoKSRMFCXQY5oac uTmyPIT4STFyUQFeqSCWDum/NFNoSKhmItw2Td+4VSJHShRVbg39KNFPZ7mXYAkQiKkGTRg1 YesWJA/+PV3qDUtPNEGwjVvjQqHSbrBy94tu6gJvPHgGPtRDYvxnCaJsmgiC0pGB2KFRsnfl 2zBNBEWF/XwsI081jQE5UO60GKmHTputChLXpVobyuc+lroG2YhknXRBAV969SLnZR4BS/1s Gi046gOXfaKYatve8BiZr5it5Foq3FMPDNgZMit1H9Dk8rkKFfDMRf8EGS/Z+TmyEsIf99H7 TH3n7lco8qO81fSFwkh4pvo2kWRFYTC5vsIVQ+GqVUp+W1DZJHxX8LwWuF1AzUt4MUTtNAvy TXl5EgsmoY9mpNNL7ZnW65oG63nEP5KNiybvuQJzXVxR8eqzOh2Mod4nHg3PE7UCd3DvLNsn GXFRo44WyT/G2lArBtjpkut7bDm0i1nENABy2UgS+1QvdmgNu6aEZxdNthwRjUhuuvCCDMA4 rCDQYyakH2tJNQgkXkeLodBKF4bHiBbuwj0E39S9wmGgg+q4OTnAO/yhQGknle7a7G5xHBwE i0HjnLoJP5jDcoMTabZTIazXmJz3pKM11HYJ5/ZsTIf3ZRJJKIvXJpbmcAPVwTZII6XxiJdh RSSX4Mvd5pL/+5WI6NTdW6DMfigTtdd85fe6PwBNVJL2ZvBfsBJZ5rxg1TOH3KLsYBqBTgW2 glQofxhkJhDEcvjLhe3Y2BlbCWKOmvM8XS9TRt0OwUs= Message-ID: <4ee9736d-4e49-6572-e6e8-94739d155323@redhat.com> Date: Mon, 15 Jul 2019 20:13:13 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <87a7ew9p3o.fsf@dusky.pond.sub.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Tue, 16 Jul 2019 00:13:17 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] qapi: add dirty-bitmaps to query-named-block-nodes result 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: , Cc: kwolf@redhat.com, Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org, qemu-devel@nongnu.org, mreitz@redhat.com, nshirokovskiy@virtuozzo.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/5/19 8:46 AM, Markus Armbruster wrote: > John Snow writes: > >> On 5/31/19 10:55 AM, Eric Blake wrote: >>> On 5/30/19 11:26 AM, John Snow wrote: >>>> >>>> >>>> On 5/30/19 10:39 AM, Vladimir Sementsov-Ogievskiy wrote: >>>>> Let's add a possibility to query dirty-bitmaps not only on root nodes. >>>>> It is useful when dealing both with snapshots and incremental backups. >>>>> >>> >>>>> +++ b/block/qapi.c >>>>> @@ -78,6 +78,11 @@ BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk, >>>>> info->backing_file = g_strdup(bs->backing_file); >>>>> } >>>>> >>>>> + if (!QLIST_EMPTY(&bs->dirty_bitmaps)) { >>>>> + info->has_dirty_bitmaps = true; >>>>> + info->dirty_bitmaps = bdrv_query_dirty_bitmaps(bs); >>>>> + } >>>>> + >>>>> info->detect_zeroes = bs->detect_zeroes; >>>>> >>>>> if (blk && blk_get_public(blk)->throttle_group_member.throttle_state) { >>>>> >>>> >>>> So query-block uses bdrv_query_info, which calls bdrv_block_device_info, >>>> so we'll duplicate the bitmap output when doing the old-fashioned block >>>> query, but that's probably harmless overall. >>> >>> We already know that none of our existing query- interfaces are sane >>> (either too little information, or too much). Duplication starts to >>> push an interface towards too much (it takes processor time to bundle up >>> the extra JSON, especially if the other end is not going to care if it >>> was present). I know Kevin still has somewhere on his to-do list the >>> implementation of a saner query- command for the information we really >>> want (about each block, without redundant information, and where we >>> don't repeat information in a nested manner, but where we also don't >>> omit information that would otherwise require multiple existing query- >>> to reconstruct). >>> >>>> >>>> We can continue to support the output in both places, or we could opt to >>>> deprecate the older interface; I think this is one of the last chances >>>> we'd get to do so before libvirt and wider adoption. >>>> >>>> I think that's probably Eric's choice. >>> >>> If you want to try to deprecate the old location, introspection at least >>> works to allow libvirt to know which place to look for it on a given >>> qemu. If you don't think deprecation is necessary, the duplication is >>> probably tolerable for now (as ideally we'd be deprecating ALL of our >>> not-quite-perfect query- block interfaces in favor of whatever sane >>> interface Kevin comes up with). >>> >> >> It sounds like it's probably the right move to deprecate the entire >> legacy interface, but still... If you have 20 or 30 bitmaps on a root >> node, you will see 40 or 60 entries. >> >> What's the smart way to deprecate it? We're not adding new flags or >> showing new arguments or anything. There might not be bitmaps, so you >> can't rely on that field being present or absent. >> >> Recommendations? > > Kevin's "[PATCH v4 0/6] file-posix: Add dynamic-auto-read-only QAPI > feature" adds "feature flags" to the QAPI schema language, limited to > struct types, because that's what he needs. They're visible in > introspection. I intend to complete his work, so we can tack > "deprecated" feature flags to pretty much anything > > Could that address your need? > Hi Markus, digging this up again. In brief, we are displaying bitmap info in the "wrong" part of the query result (attached to drive instead of node) and would like to change it. I'd like to avoid reporting bitmaps in both locations permanently, so if we have a plan to deprecate reporting bitmaps in the old location, I will tolerate the duplicated output temporarily. Keeping in mind the bitmap fields are optional (so they can be absent from both the new and old locations), what plan can we implement? Perhaps I can add a feature flag "has-node-bitmaps" for 4.2. Then, for the next three versions, I will report bitmaps from both locations. Then, in 5.2+ I will remove the old location. A client knows it can find bitmaps (if there are any) in the new location if the feature flag is set. Otherwise, it should look in the old location. I think I've convinced myself that this is correct, so correct me if I am wrong. --js