Re: [BUG] famous "rbd: unmap failed: (16) Device or resource busy" trapped

Hello I work on the famous "rbd: unmap failed: (16) Device or resource busy" which causes problems for some projects such as Incus (LXD), and many people just live with it... I post it on the ceph-user M/L and Murilo Morais works for several days with me on it. https://discuss.linuxcontainers.org/t/incus-0-x-and-ceph-rbd-map-is-sometim… <= Work with Stephane Graber INCUS/LXD main developer => https://discuss.linuxcontainers.org/t/howto-delete-container-with-ceph-rbd-… I work on an easy reproducible bug setup without any other tool than stock ceph setup : create an image, map it, format&mount it, ADD AN OSD, and try to unmap the image ... tada ! "rbd: unmap failed: (16) Device or resource busy" is here. Here's the more complete explanation, (who is the great job of Murilo Morais) : *I managed to reproduce.The problem is how docker/podman binds "/" to "/rootfs" in containers.When ceph creates the files for SystemD to start the services, it includes a system root bind to /rootfs [1], I do not recommend removing this bind, as it will break MON.* *By default they use "rprivate" [2][3], it causes the mount points to be propagated to the container but does not receive any "mount" or "umount" events from the host [4]. This causes this behavior in your cluster.* *This will happen whenever any container starts/restarts, regardless of whether it is a new daemon or not.* *A quick alternative would be to change the unit files in /var/lib/ceph/<fsid>/<daemon>/ and add "slave" or "rslave" to the podman bind argument. Where it contains "-v /:/rootfs" add ":slave", leaving "-v /:/rootfs:slave". The inconvenience is that it will be necessary to restart all daemons, and, when adding/redeploying a daemon, you will have to perform the same steps.*

*A definitive solution would be to change the source code, but I didn't have time to try this option. Tomorrow, as soon as I get to the office, I will try to do this, I will report back to you as soon as I discover something!*

*If you wish, you can respond to the public list about your problem and the need to change the bind to rootfs, for everyone to see and so that some of the project's devs can perhaps comment on something.*

*Have a good night!* *[1] https://github.com/ceph/ceph/blob/7714874efb08facee80f92b358993fa56854bb01/… <https://github.com/ceph/ceph/blob/7714874efb08facee80f92b358993fa56854bb01/src/cephadm/cephadmlib/daemons/ceph.py#L423>* *[2] https://docs.docker.com/storage/bind-mounts/#configure-bind-propagation <https://docs.docker.com/storage/bind-mounts/#configure-bind-propagation>* *[3] https://docs.podman.io/en/latest/markdown/podman-create.1.html#mount-type-t… <https://docs.podman.io/en/latest/markdown/podman-create.1.html#mount-type-type-type-specific-option>* *[4] https://man7.org/linux/man-pages/man7/mount_namespaces.7.html <https://man7.org/linux/man-pages/man7/mount_namespaces.7.html>* And the reproduction log is : First I create a new image and map it (to be alone from Incus) : root@ceph02-r2b-fl1:~# ceph osd tree ID CLASS WEIGHT TYPE NAME STATUS REWEIGHT PRI-AFF -1 53.12473 root default ... -5 3.63879 host ceph02-r2b-fl1 6 hdd 0.90970 osd.6 up 1.00000 1.00000 9 hdd 0.90970 osd.9 up 1.00000 1.00000 2 nvme 0.90970 osd.2 up 1.00000 1.00000 4 nvme 0.90970 osd.4 up 1.00000 1.00000 ... root@ceph02-r2b-fl1:~# rbd create image1 --size 1024 --pool customers-clouds.ix-mrs2.fr.eho root@ceph02-r2b-fl1:~# RBD_DEVICE=$(rbd map customers-clouds.ix-mrs2.fr.eho/image1) root@ceph02-r2b-fl1:~# mkfs.ext4 ${RBD_DEVICE} mke2fs 1.47.0 (5-Feb-2023) Discarding device blocks: done Creating filesystem with 262144 4k blocks and 65536 inodes Filesystem UUID: c97362e1-11db-4ff3-ba62-ede6d58884b9 Superblock backups stored on blocks: 32768, 98304, 163840, 229376 Allocating group tables: done Writing inode tables: done Creating journal (8192 blocks): done Writing superblocks and filesystem accounting information: done root@ceph02-r2b-fl1:~# mount ${RBD_DEVICE} /media/test Let's list current mapped devices. *root@ceph02-r2b-fl1:~# mount | grep rbd/dev/rbd4 on /var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd5 on /var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd2 on /var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd1 on /var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd3 on /var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd0 on /var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd6 on /media/test type ext4 (rw,relatime,stripe=16)* ============================================================================================ ===============> Adding the new OSD (an old small disk to be faster...) <=================== =========================== (via service task in dashboard) ================================ ============================================================================================ root@ceph02-r2b-fl1.ep-ws.fr.eholab.admin:~# ceph osd tree ID CLASS WEIGHT TYPE NAME STATUS REWEIGHT PRI-AFF -1 53.25822 root default ... -5 3.77229 host ceph02-r2b-fl1 6 hdd 0.90970 osd.6 up 1.00000 1.00000 9 hdd 0.90970 osd.9 up 1.00000 1.00000 * 26 hdd 0.13350 osd.26 up 1.00000 1.00000 <=== Here's the brand new OSD* 2 nvme 0.90970 osd.2 up 1.00000 1.00000 4 nvme 0.90970 osd.4 up 1.00000 1.00000 .... ============ Let's check what is NS contains ... ======================= root@ceph02-r2b-fl1:~# podman ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES ..... 6dbd4fd4e4f3 cephpodregistry:5000/ceph@sha256:e205163225ec8ce460d6581df66ba4866585e3a4817866910f85bedcdcff7935 -n osd.26 -f --se... 2 minutes ago Up 2 minutes ago ceph-c3f59906-c43d-11ee-a2d6-3a82cb8036b6-osd-26 *root@ceph02-r2b-fl1.ep-ws.fr.eholab.admin:~# podman exec 6dbd4fd4e4f3 mount | grep rbd/dev/rbd4 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd5 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd2 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd1 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd3 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd0 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-xx type ext4 (rw,relatime,discard,stripe=16)/dev/rbd6 on /rootfs/media/test type ext4 (rw,relatime,stripe=16)======= of course these mountpoints are not needed by the newly created OSD ... and this full copy is problematic ============* And then : root@ceph02-r2b-fl1:~# umount /dev/rbd6 -I can unmount the rbd device ... no reference is host NS- *root@ceph02-r2b-fl1:~# rbd unmap /dev/rbd6rbd: sysfs write failedrbd: unmap failed: (16) Device or resource busy* *root@ceph02-r2b-fl1:~# podman exec 6dbd4fd4e4f3 mount | grep rbd/dev/rbd4 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-06c995c3 type ext4 (rw,relatime,discard,stripe=16)/dev/rbd5 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-0bc99da2 type ext4 (rw,relatime,discard,stripe=16)/dev/rbd2 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-62cc652e type ext4 (rw,relatime,discard,stripe=16)/dev/rbd1 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-5dcc5d4f type ext4 (rw,relatime,discard,stripe=16)/dev/rbd3 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-efd3feea type ext4 (rw,relatime,discard,stripe=16)/dev/rbd0 on /rootfs/var/lib/incus/storage-pools/default/containers/ec-59cc5703 type ext4 (rw,relatime,discard,stripe=16)/dev/rbd6 on /rootfs/media/test type ext4 (rw,relatime,stripe=16)* ... Because OSD's Namespace still had the mount (as all rbd mapped...) Hope someone could create a ticket for this bug in ceph bug tracker. I didn't find how to create a ticket without being "a member". Regards Nicolas FOURNIL https://www.eho.link _______________________________________________ Dev mailing list -- dev(a)ceph.io To unsubscribe send an email to dev-leave(a)ceph.io