From mboxrd@z Thu Jan 1 00:00:00 1970 From: Loic Dachary Subject: PGLog::rewind_divergent_log use case Date: Sat, 08 Jun 2013 10:16:13 +0200 Message-ID: <51B2E84D.6090001@dachary.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig7A1600824AF02EE5442442B8" Return-path: Received: from smtp.dmail.dachary.org ([86.65.39.20]:59374 "EHLO smtp.dmail.dachary.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751447Ab3FHIQS (ORCPT ); Sat, 8 Jun 2013 04:16:18 -0400 Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Samuel Just Cc: Ceph Development This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig7A1600824AF02EE5442442B8 Content-Type: multipart/mixed; boundary="------------000805040801010709040404" This is a multi-part message in MIME format. --------------000805040801010709040404 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable [Note: ceph-devel cc'ed] Hi Sam, While trying to create the conditions for the following to happen in PGLo= g::rewind_divergent_log: if (p =3D=3D log.log.begin()) { // yikes, the whole thing is divergent! divergent.swap(log.log); break; } https://github.com/ceph/ceph/blob/master/src/osd/PGLog.cc#L355 I created this ( matching the drawing attached ), and the test case works= =2E=20 { pg_log_entry_t e; info.log_tail =3D log.tail =3D eversion_t(1, 1); newhead =3D eversion_t(1, 3); e.version =3D divergent_version =3D eversion_t(1, 5); e.soid.hash =3D 0x9; divergent_object =3D e.soid; e.op =3D pg_log_entry_t::DELETE; e.prior_version =3D prior_version =3D eversion_t(0, 2); log.log.push_back(e); log.head =3D e.version; } https://github.com/dachary/ceph/commit/d592d7f10968c56139cb470a4111ddfbe0= 8a4030#L0R136 But it does not look like a situation that is actually going to happen. I= feel something is missing and a hint would be much appreciated :-) Cheers --=20 Lo=EFc Dachary, Artisan Logiciel Libre All that is necessary for the triumph of evil is that good people do noth= ing. --------------000805040801010709040404 Content-Type: image/png; name="a.png" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="a.png" iVBORw0KGgoAAAANSUhEUgAAAa4AAADuCAIAAADuuHQVAAAXe0lEQVR42u2de0yV5R/A5X5x iEIoIlqAF0IUzHUBvINRM52pqZnmZVOn5bKNNtyc2pzNksw/NB2tcRO1oKwVCgvvWqg05gXT ZComlNAgQASB8Pf98ax377gcD+cc4ACfzx9nz/O8l3Oe5znfz3me857zPn0eAwD0evrQBAAA qBAAABUCAKBCAABUCACACgEAUCEAACoEAECFAACoEAAAFQIAoEIAAFQIAIAKAQBQIQAAKgQA QIUAAKgQAAAVAgCgQgAAVAgAgAoBAFAhAAAqBABAhQAAqBAAABUCAKBCAABUCACACgEAUCEA ACoEAECFAACoEAAAFT6BwMDAPtBbkd5HAYAKm+rfh3ExvQ+ACgkGeh8AFRIM9D4AKiQY6H0A VEgw0PsAqJBgoPdpBECFBAMqpPcBFXZkMKifrfH2QoWAClEhYYYKARWiQsIMFQIqRIX6M2dl ZU2YMMHV1dXFxSUiIkKy+p33798fEBDg4OAQFBSUlJSERlEhoMIeqEIRn62tbVhY2J07dwoL 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