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Thu, 4 Jun 2020 21:34:07 +0000 From: Alexander Mikhalitsyn To: Amir Goldstein CC: Miklos Szeredi , Andrey Vagin , Pavel Tikhomirov , Konstantin Khorenko , Vasiliy Averin , Kirill Tkhai , overlayfs , linux-kernel Subject: Re: [PATCH 0/2] overlayfs: C/R enhancements Thread-Topic: [PATCH 0/2] overlayfs: C/R enhancements Thread-Index: AQHWOosBznFYrKt2fUuocLUlO0auLajIwDoAgAAt+xQ= Date: Thu, 4 Jun 2020 21:34:07 +0000 Message-ID: References: <20200604161133.20949-1-alexander.mikhalitsyn@virtuozzo.com>, In-Reply-To: Accept-Language: en-US, ru-RU Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: gmail.com; dkim=none (message not signed) header.d=none;gmail.com; dmarc=none action=none header.from=virtuozzo.com; x-originating-ip: [91.76.135.191] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: d0f82c1a-3fcb-481f-d91e-08d808cf0318 x-ms-traffictypediagnostic: AM6PR08MB3351: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:9508; 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charset="us-ascii" MIME-Version: 1.0 X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-Network-Message-Id: d0f82c1a-3fcb-481f-d91e-08d808cf0318 X-MS-Exchange-CrossTenant-originalarrivaltime: 04 Jun 2020 21:34:07.4888 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: qSiyjT2ZaLizWWWOl29jjoiSQKrhfRa9u+OaBZtCbDSxRPCsytpcx9ms8tdr0OmJhXe7l/0F7nrcCL+ptcuKJJsCsDU69/VvGwZOQLHF0dngZc3ZhwIrjXjxykZI0Z2E X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB3351 Sender: linux-unionfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org Hello, >But overlayfs won't accept these "output only" options as input args, which is a problem. Will it be problematic if we simply ignore "lowerdir_mnt_id" and "upperdir_mnt_id" options in ovl_parse_opt()? >Wouldn't it be better for C/R to implement mount options that overlayfs can parse and pass it mntid and fhandle instead of paths? Problem is that we need to know on C/R "dump stage" which mounts are used on lower layers and upper layer. Most likely I don't understand something but I can't catch how "mount-time" options will help us. >I believe C/R is using a similar method to export inotify/fanotify marks. Yes, we are using fhandles to C/R inotify/fanotify. On "dump" we get fhandle from /proc//fdinfo and on "restore" we open fhandle through open_by_handle_at() syscall. Regards, Alex ________________________________________ From: Amir Goldstein Sent: Thursday, June 4, 2020 21:04 To: Alexander Mikhalitsyn Cc: Miklos Szeredi; Andrey Vagin; Pavel Tikhomirov; Konstantin Khorenko; Vasiliy Averin; Kirill Tkhai; overlayfs; linux-kernel Subject: Re: [PATCH 0/2] overlayfs: C/R enhancements On Thu, Jun 4, 2020 at 7:13 PM Alexander Mikhalitsyn wrote: > > This patchset aimed to make C/R of overlayfs mounts with CRIU possible. > We introduce two new overlayfs module options -- dyn_path_opts and > mnt_id_path_opts. If enabled this options allows to see real *full* paths > in lowerdir, workdir, upperdir options, and also mnt_ids for corresponding > paths. > > This changes should not break anything because for showing mnt_ids we simply > introduce new show-time mount options. And for paths we simply *always* > provide *full paths* instead of relative path on mountinfo. > > BEFORE > > overlay on /var/lib/docker/overlay2/XYZ/merged type overlay (rw,relatime, > lowerdir=/var/lib/docker/overlay2/XYZ-init/diff:/var/lib/docker/overlay2/ > ABC/diff,upperdir=/var/lib/docker/overlay2/XYZ/diff,workdir=/var/lib/docker > /overlay2/XYZ/work) > none on /sys type sysfs (rw,relatime) > > AFTER > > overlay on /var/lib/docker/overlay2/XYZ/merged type overlay (rw,relatime, > lowerdir=/var/lib/docker/overlay2/XYZ-init/diff:/var/lib/docker/overlay2/ > ABC/diff,upperdir=/var/lib/docker/overlay2/XYZ/diff,workdir=/var/lib/docker > /overlay2/XYZ/work,lowerdir_mnt_id=175:175,upperdir_mnt_id=175) > none on /sys type sysfs (rw,relatime) > But overlayfs won't accept these "output only" options as input args, which is a problem. Wouldn't it be better for C/R to implement mount options that overlayfs can parse and pass it mntid and fhandle instead of paths? I believe C/R is using a similar method to export inotify/fanotify marks. FWIW overlayfs already has utilities that encode filehandle to text and back, see ovl_get_index_name(). Thanks, Amir.