Thanks, I didn't wrote to /sys/block/bcache0/bcache/stop, I missed this as I was only looking in /dev/bcache* and in /sys/fs/bcache; which explains why I was left with an used device.
I agree that the interface is not very user-fiendly, we may need to improve the bcache-tools command to simplify this. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1377142 Title: Bcache doesn't allow full unregistering without rebooting Status in “bcache-tools” package in Ubuntu: New Status in “linux” package in Ubuntu: Incomplete Bug description: If you create a bcache device, you can't reuse all your disk/partitions without a reboot. You can reproduce the case this way: start a vm with 2 disks (caching must be bigger or equal to the backing cf bug :1377130) and an iso of utopic desktop amd64 create the bcache device: make-bcache --writeback --discard -C /dev/sda -B /dev/sdb UUID: b245150d-cfbe-4f90-836a-343e0e1a4c55 Set UUID: c990a31a-f531-4231-9603-d40230dc6504 version: 0 nbuckets: 16384 block_size: 1 bucket_size: 1024 nr_in_set: 1 nr_this_dev: 0 first_bucket: 1 UUID: cc31e0bb-db29-4115-a1b2-e9ff54e5f127 Set UUID: c990a31a-f531-4231-9603-d40230dc6504 version: 1 block_size: 1 data_offset: 16 ****************************** command: lsblk result: NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 8G 0 disk └─bcache0 251:0 0 16G 0 disk sdb 8:16 0 16G 0 disk └─bcache0 251:0 0 16G 0 disk sr0 11:0 1 1,1G 0 rom /cdrom loop0 7:0 0 1,1G 1 loop /rofs ****************************** All is good lsmod | grep bcache: bcache 227884 3 format the bcache device: ****************************** command: mkfs.ext4 /dev/bcache0 result: Rejet des blocs de périphérique : 4096/4194302 complété Creating filesystem with 4194302 4k blocks and 1048576 inodes Filesystem UUID: 587d2249-3eaf-4590-a00d-42939f257e99 Superblocs de secours stockés sur les blocs : 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000 Allocation des tables de groupe : 0/128 complété Écriture des tables d'i-noeuds : 0/128 complété Création du journal (32768 blocs) : complété Écriture des superblocs et de l'information de comptabilité du système de fichiers : 0/128 2/128 complété ****************************** Now mount it: mount /dev/bcache0 /mnt/ mkdir /mnt/test_dir touch /mnt/test_file state of: /sys/fs/bcache/ ls /sys/fs/bcache/ c990a31a-f531-4231-9603-d40230dc6504 register register_quiet bcache-super-show /dev/sda sb.magic ok sb.first_sector 8 [match] sb.csum E6A8D9AC496B0B04 [match] sb.version 3 [cache device] dev.label (empty) dev.uuid b245150d-cfbe-4f90-836a-343e0e1a4c55 dev.sectors_per_block 1 dev.sectors_per_bucket 1024 dev.cache.first_sector 1024 dev.cache.cache_sectors 16776192 dev.cache.total_sectors 16777216 dev.cache.ordered yes dev.cache.discard yes dev.cache.pos 0 dev.cache.replacement 0 [lru] cset.uuid c990a31a-f531-4231-9603-d40230dc6504 ****************************** bcache-super-show -f /dev/sdb sb.magic ok sb.first_sector 8 [match] sb.csum 9600B159F36A67DD [match] sb.version 1 [backing device] dev.label (empty) dev.uuid cc31e0bb-db29-4115-a1b2-e9ff54e5f127 dev.sectors_per_block 1 dev.sectors_per_bucket 1024 dev.data.first_sector 16 dev.data.cache_mode 1 [writeback] dev.data.cache_state 2 [dirty] cset.uuid c990a31a-f531-4231-9603-d40230dc6504 ****************************** mount: /dev/bcache0 on /mnt type ext4 (rw) we will unregister the bcache: echo 1 /sys/fs/bcache/c990a31a-f531-4231-9603-d40230dc6504/unregister check the content of /sys/fs/bcache ls /sys/fs/bcache/ register register_quiet So bcache is unregistered, but status of /dev/sda: bcache-super-show -f /dev/sda sb.magic ok sb.first_sector 8 [match] sb.csum E6A8D9AC496B0B04 [match] sb.version 3 [cache device] dev.label (empty) dev.uuid b245150d-cfbe-4f90-836a-343e0e1a4c55 dev.sectors_per_block 1 dev.sectors_per_bucket 1024 dev.cache.first_sector 1024 dev.cache.cache_sectors 16776192 dev.cache.total_sectors 16777216 dev.cache.ordered yes dev.cache.discard yes dev.cache.pos 0 dev.cache.replacement 0 [lru] cset.uuid c990a31a-f531-4231-9603-d40230dc6504 command: bcache-super-show -f /dev/sdb result: sb.magic ok sb.first_sector 8 [match] sb.csum D41799F794675FA8 [match] sb.version 1 [backing device] dev.label (empty) dev.uuid cc31e0bb-db29-4115-a1b2-e9ff54e5f127 dev.sectors_per_block 1 dev.sectors_per_bucket 1024 dev.data.first_sector 16 dev.data.cache_mode 1 [writeback] dev.data.cache_state 0 [detached] cset.uuid 00000000-0000-0000-0000-000000000000 ****************************** Maybe I'm wrong, but I would expect the cahing device to be 000000000ed not the backing device, as we may still want to use the data on it. But data is still accessible on the mount point. So we wipe /dev/sda now: ****************************** command: wipefs -a /dev/sda result: /dev/sda: 16 bytes were erased at offset 0x00001018 (bcache): c6 85 73 f6 4e 1a 45 ca 82 65 f5 7f 48 ba 6d 81 ****************************** mount: /dev/bcache0 on /mnt type ext4 (rw) data still there: ****************************** command: ls /mnt/ result: lost+found test_dir test_file ****************************** ****************************** command: lsblk result: NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 8G 0 disk sdb 8:16 0 16G 0 disk └─bcache0 251:0 0 16G 0 disk /mnt sr0 11:0 1 1,1G 0 rom /cdrom loop0 7:0 0 1,1G 1 loop /rofs ****************************** Ok now we can backup our data if we need to, next, we will umount: umount /mnt/ ok no errors. lsblk: NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 8G 0 disk sdb 8:16 0 16G 0 disk └─bcache0 251:0 0 16G 0 disk sr0 11:0 1 1,1G 0 rom /cdrom loop0 7:0 0 1,1G 1 loop /rofs ****************************** bcache0 is still there, ok, but how to delete to unregister it definitively? ls /sys/fs/bcache/ result: register register_quiet ************** lsmod result: Module Size Used by bcache 227884 1 we can't wipefs -a /dev/sdb, device is in use, so we reboot machine (NOT OK) in the vm: ls /sys/fs/bcache/ result: register register_quiet update packages and reinstall bcache-tools: bcache-super-show -f /dev/sda result: Invalid superblock (bad magic) sb.magic bad magic bcache-super-show -f /dev/sdb result: sb.magic ok sb.first_sector 8 [match] sb.csum D41799F794675FA8 [match] sb.version 1 [backing device] dev.label (empty) dev.uuid cc31e0bb-db29-4115-a1b2-e9ff54e5f127 dev.sectors_per_block 1 dev.sectors_per_bucket 1024 dev.data.first_sector 16 dev.data.cache_mode 1 [writeback] dev.data.cache_state 0 [detached] cset.uuid 00000000-0000-0000-0000-000000000000 Now we can wipe /dev/sdb because we rebooted, and bcache don't use the device anymore: wipefs -a /dev/sdb result: /dev/sdb: 16 bytes were erased at offset 0x00001018 (bcache): c6 85 73 f6 4e 1a 45 ca 82 65 f5 7f 48 ba 6d 81 ********************************************************** Now I can re-use my device, but I needed a reboot. Maybe we also must have better bcache management tools. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/bcache-tools/+bug/1377142/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
