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Wed, 5 Feb 2020 15:39:00 +0000 (UTC) Date: Wed, 5 Feb 2020 16:38:59 +0100 From: Kevin Wolf To: Max Reitz Subject: Re: [PATCH v3 09/21] quorum: Add QuorumChild.to_be_replaced Message-ID: <20200205153859.GE5768@dhcp-200-226.str.redhat.com> References: <20200130214431.333510-1-mreitz@redhat.com> <20200130214431.333510-10-mreitz@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200130214431.333510-10-mreitz@redhat.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: d6WxjyM2MBm4RGBDzo7iwA-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 30.01.2020 um 22:44 hat Max Reitz geschrieben: > We will need this to verify that Quorum can let one of its children be > replaced without breaking anything else. >=20 > Signed-off-by: Max Reitz > --- > block/quorum.c | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) >=20 > diff --git a/block/quorum.c b/block/quorum.c > index 59cd524502..6a7224c9e4 100644 > --- a/block/quorum.c > +++ b/block/quorum.c > @@ -67,6 +67,13 @@ typedef struct QuorumVotes { > =20 > typedef struct QuorumChild { > BdrvChild *child; > + > + /* > + * If set, check whether this node can be replaced without any > + * other parent noticing: Unshare CONSISTENT_READ, and take the > + * WRITE permission. > + */ > + bool to_be_replaced; I don't understand these permission changes. How does (preparing for) detaching a node from quorum make its content invalid? And why do we suddenly need WRITE permissions even if the quorum node is only used read-only? The comment is a bit unclear, too. "check whether" implies that both outcomes could be true, but it doesn't say what happens in either case. Is this really "make sure that"? Kevin