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Thu, 20 Jun 2019 15:25:07 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.208]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0685E60BE0; Thu, 20 Jun 2019 15:25:02 +0000 (UTC) To: John Snow , qemu-devel@nongnu.org, qemu-block@nongnu.org References: <20190620010356.19164-1-jsnow@redhat.com> <20190620010356.19164-4-jsnow@redhat.com> From: Max Reitz Openpgp: preference=signencrypt Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: Date: Thu, 20 Jun 2019 17:25:01 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190620010356.19164-4-jsnow@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="BsFCE9uDTTd3EszbRCONjWk5HAQHSYbqF" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Thu, 20 Jun 2019 15:25:07 +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 03/12] block/backup: add 'never' policy to bitmap sync mode 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: Kevin Wolf , Fam Zheng , vsementsov@virtuozzo.com, Wen Congyang , Xie Changlong , Markus Armbruster Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --BsFCE9uDTTd3EszbRCONjWk5HAQHSYbqF Content-Type: multipart/mixed; boundary="g2RNTy14zQclwpZkQ73H49fnymtxgOSXG"; protected-headers="v1" From: Max Reitz To: John Snow , qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: Kevin Wolf , Wen Congyang , eblake@redhat.com, vsementsov@virtuozzo.com, Markus Armbruster , Fam Zheng , Xie Changlong Message-ID: Subject: Re: [PATCH 03/12] block/backup: add 'never' policy to bitmap sync mode References: <20190620010356.19164-1-jsnow@redhat.com> <20190620010356.19164-4-jsnow@redhat.com> In-Reply-To: <20190620010356.19164-4-jsnow@redhat.com> --g2RNTy14zQclwpZkQ73H49fnymtxgOSXG Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 20.06.19 03:03, John Snow wrote: > This adds a "never" policy for bitmap synchronization. Regardless of if= > the job succeeds or fails, we never update the bitmap. This can be used= > to perform differential backups, or simply to avoid the job modifying a= > bitmap. >=20 > Signed-off-by: John Snow > --- > qapi/block-core.json | 6 +++++- > block/backup.c | 5 +++-- > 2 files changed, 8 insertions(+), 3 deletions(-) >=20 > diff --git a/qapi/block-core.json b/qapi/block-core.json > index 6d05ad8f47..0332dcaabc 100644 > --- a/qapi/block-core.json > +++ b/qapi/block-core.json > @@ -1146,10 +1146,14 @@ > # @conditional: The bitmap is only synchronized when the operation is = successul. > # This is useful for Incremental semantics. > # > +# @never: The bitmap is never synchronized with the operation, and is > +# treated solely as a manifest of blocks to copy. > +# This is useful for Differential semantics. > +# Again, this is too buzzword-y for my taste. I don=E2=80=99t find it as b= ad because there is not much to explain about this mode, and you do explain it above, but still. Like, I (me myself) read this and after the first sentence I think I=E2=80= =99ve understood what this is. Then I read =E2=80=9Cfor Differential semantics= =E2=80=9D and I=E2=80=99m confused. After a couple of seconds, I realize what you mean= because I=E2=80=99ve described in my response to patch 1. One reason it leaves the buzzword-y taste is because =E2=80=9Cdifferentia= l=E2=80=9D is never explained anywhere. bitmaps.rst makes two mentions of it, but it too just assumes I know what you mean. Also, incremental backups are just a certain kind of differential backups. So you need to explain =E2=80=9Cdifferential=E2=80=9D somewhere and how i= t differs from =E2=80=9Cincremental=E2=80=9D in this regard. Why not here? =E2=80=9CThis is useful when you wish to repeatedly perform operations in= reference to a constant synchronization point (when the bitmap was created).=E2=80=9D Or something. Max > # Since: 4.1 > ## > { 'enum': 'BitmapSyncMode', > - 'data': ['conditional'] } > + 'data': ['conditional', 'never'] } > =20 > ## > # @MirrorCopyMode: --g2RNTy14zQclwpZkQ73H49fnymtxgOSXG-- --BsFCE9uDTTd3EszbRCONjWk5HAQHSYbqF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl0LpU0ACgkQ9AfbAGHV z0BKxwf8DixyOX4AbowOWamDs0MTCIJv4QtNHPndH1iiOj8aiPx+lSKfG92jWgXY SCTg9zOm7b3Xxtcbs/UOnVGZet/SWJUtBQoItk4aXrsJYxjLfsRzmzbk01+HEJ9f zLBIa7IGPXpfJmXqbAMxNsSr0K+TgyHJSGA+wMLNbDXUtITjX8tM2hgYhtFc3hEZ jUlLdD/lK2uzLXtp0LQDaDo+njrjWJCjJ85K1fVRLtfeGq/MNYXWQTDssMu2UqHP 28gPMVCFvW1GyhiSeEVulXMqmAmK63co8XGmypNU7dnmVqt5YMSjWv97C36IlomW H/Sg428AoGsOWG37Og+0OZW/DP+YXw== =mC4w -----END PGP SIGNATURE----- --BsFCE9uDTTd3EszbRCONjWk5HAQHSYbqF--