[disclaimer: haven't tried bcache on / myself] from the manual steps given, I think there needs to also be an attaching operation: echo "<cset-uuid>" >/sys/block/dm-xy/bcache/attach Not sure why often the backing device must be explicitly attached to the caching device to make /dev/bcache<n> show up. Perhaps some cleanup left to do, so it doesn't want to be mountable without its caching device. You should put "bcache" into /etc/modules und run update-initramfs, otherwise the bcache module will not be ready when the kernel needs it for mounting the real root device. More tweaks might be necessary, don't know if that already gives you the udev rules inside the initramfs (it should, if you have bcache-tools installed which provide initramfs-tools/hooks/bcache). Regards Matthias On Wed, Dec 11, 2013 at 10:02:32AM -0500, Zachary Palmer wrote: > I ran into a couple of problems when installing a similar bcache > config on my laptop. A few things to check: > > 1. While I have no experience with Suse, Debian has a directory > /etc/initramfs/hooks/bcache containing a script which is executed > when the initramfs image is built. bcache-tools places a script > there on my system which ensures that the bcache module and binaries > are present in my initramfs. > > 2. Similarly, bcache-tools installs a file > /lib/udev/rules.d/61-bcache.rules which teaches udev to recognize > and register bcache devices. > > 3. For an older version of bcache (I don't know if this is the case > anymore), I had to put a file at > /etc/initramfs-tools/scripts/init-premount/z-bcache (please see > attached). This file is executed during the initramfs phase of boot > and will crudely throw every /dev/sd* at the bcache module for > inspection. I wouldn't use this unless you need it, but it gets the > job done on my system. > > You gave an excellent walkthrough of what you're doing, but I notice > that you didn't indicate installing bcache-tools on the system. > (You installed it under the LiveCD, but not the system itself.) It > seems at this point like you should: > > 1. Boot the Ubuntu LiveCD > 2. Install bcache-tools and get your system's root and boot > partitions mounted somewhere > 3. chroot into that directory > 4. Install bcache-tools under the Suse root and make sure your > initramfs is updated > 5. Unmount cleanly and reboot > > I'm hoping I've diagnosed things correctly. If so, the lesson: > bcache-tools is doing more than just providing you a couple of > binaries; it also teaches udev and initramfs a few things. :) > > Cheers, > > Zach > >Hello, > > > >I'm new to using bcache and am having difficulty assembling and > >mounting the /dev/bcache* devices after their initial creation, at > >which time I can mount them. > > > >My goal to to have the root file system as as bcache device. Currently > >booting fails as it can't find the root device, which makes sense > >given I'm unable to create and mount it from a live environment as > >well - although agagin I can mount it fine at time of creation. > > > >Following is the process I am using. I'd really love to get this > >working and would appreciate any tips on where I'm going wrong. > > > >Thanks in advance! > >Pete > > > >== Initial Config == > > > >Installed Suse 13.1 using normal Suse installer, with /boot, / and > >swap. / is btrfs and LVM. > > > >Booted to Ubuntu 13.10 live CD, installed bcache-tools and blocks from > >ppa:g2p/storage > > > >Used blocks to convert /dev/mapper/system-root to bcache > > > >Run make-bache on /dev/mapper/system-root, and /dev/sdb (the SSD) and > >joined using th cset ID provided. This appears to have succeeded, and > >after which I was able to mount /dev/bcache1 and the cache (per stats > >is /sys) was working correctly. All appeared good. > > > >However, after rebooting I am unable to mount it again as I am never > >able to get the /dev/bcache* devices to appear again. > > > >== Subsequent reboot, no /dev/bcache* devices == > > > >Here is what I see on the subsequent reboot from Ubuntu 13.10 Live CD: > > > >No /sys/fs/bcache on boot: > > > >root@ubuntu:~# ls /sys/fs/ > >btrfs/ cgroup/ ecryptfs/ ext4/ fuse/ pstore/ > > > >Add bcahce tools (and blocks): > > > >apt-add-repository ppa:g2p/storage > >apt-get update > >apt-get install bcache-tools python3-blocks > > > >Attempting to make-bcache again results in bcache device appearing in /sys/fs: > > > >root@ubuntu:~# make-bcache -C /dev/sdb > >Already a bcache device on /dev/sdb, overwrite with --wipe-bcache > > > >root@ubuntu:~# ls /sys/fs/ > >bcache/ btrfs/ cgroup/ ecryptfs/ ext4/ fuse/ pstore/ > > > >Register the devices: > >root@ubuntu:~# echo /dev/mapper/system-root > /sys/fs/bcache/register > >root@ubuntu:~# echo /dev/sdb > /sys/fs/bcache/register > >bash: echo: write error: Invalid argument > > > >Perhaps /dev/sdb alredy registered from failed make-bcache above? > >root@ubuntu:~# dmesg | tail > >[ 559.438930] bcache: register_bcache() error opening /dev/sdb: > >device already registered > > > > > >Examine backing and cache devices superblocks: > > > >root@ubuntu:~# bcache-super-show /dev/mapper/system-root > >sb.magic ok > >sb.first_sector 8 [match] > >sb.csum 815BCC6A0F4B43B6 [match] > >sb.version 4 [backing device] > > > >dev.label (empty) > >dev.uuid fef7635a-562d-4493-bc9a-eb56eca00609 > >dev.sectors_per_block 1 > >dev.sectors_per_bucket 1024 > >dev.data.first_sector 8192 > >dev.data.cache_mode 1 [writeback] > >dev.data.cache_state 1 [clean] > > > >cset.uuid 00000000-0000-0000-0000-000000000000 > > > >root@ubuntu:~# bcache-super-show /dev/sdb > >sb.magic ok > >sb.first_sector 8 [match] > >sb.csum 7E3113141FAB5928 [match] > >sb.version 3 [cache device] > > > >dev.label (empty) > >dev.uuid 897e3a51-4e38-455c-8989-efffcb707be4 > >dev.sectors_per_block 1 > >dev.sectors_per_bucket 1024 > >dev.cache.first_sector 1024 > >dev.cache.cache_sectors 234439680 > >dev.cache.total_sectors 234440704 > >dev.cache.ordered yes > >dev.cache.discard no > >dev.cache.pos 0 > >dev.cache.replacement 0 [lru] > > > >cset.uuid 01f294ff-6898-46b1-9c39-dcba3df35a8c > > > > > >root@ubuntu:~# cat /sys/block/sdb/bcache/ > >block_size clear_stats metadata_written > > written > >btree_written discard nbuckets > >bucket_size freelist_percent priority_stats > >cache_replacement_policy io_errors set/ > > > >root@ubuntu:~# ls /sys/fs/bcache/ > >01f294ff-6898-46b1-9c39-dcba3df35a8c/ register > > register_quiet > > > >root@ubuntu:~# ls /sys/fs/bcache/01f294ff-6898-46b1-9c39-dcba3df35a8c/ > >average_key_size congested_write_threshold_us stats_five_minute/ > >block_size dirty_data stats_hour/ > >btree_cache_size flash_vol_create stats_total/ > >bucket_size internal/ stop > >cache0/ io_error_halflife synchronous > >cache_available_percent io_error_limit tree_depth > >clear_stats journal_delay_ms unregister > >congested root_usage_percent > >congested_read_threshold_us stats_day/ > > > >Although cache0 shows above is /sys/fs/bcache, there still is no /dev/bcache0: > > > >root@ubuntu:~# mount /dev/b > >block/ bsg/ btrfs-control bus/ > > > >Try to rejoin? Nope. > > > >root@ubuntu:~# blocks to-bcache /dev/mapper/system-root --join > >01f294ff-6898-46b1-9c39-dcba3df35a8c > >Device /dev/mapper/system-root already has a bcache super block. > > > >What do I have to do to get /dev/bcache* devices to show again and be > >mountable? Hopefully once I figure out manual mounting I can then get > >it to be mountable as the root file system by grub2 during. > > > >Thank you again for any help. > >-- > >To unsubscribe from this list: send the line "unsubscribe linux-bcache" in > >the body of a message to majordomo@xxxxxxxxxxxxxxx > >More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > #!/bin/sh -e > > # ZEP - Added (2013-08-29) because some bcache devices were not being detected > # at startup by udev. This sloppy hack should do the job. > > PREREQS="" > > prereqs() { echo "$PREREQS"; } > > case "$1" in > prereqs) > prereqs > exit 0 > ;; > esac > > . /scripts/functions > > if [ -e '/sys/fs/bcache/register_quiet' ]; then > log_begin_msg "Scanning for bcache devices..." > for d in `ls /dev/sd*`; do > echo "$d" > /sys/fs/bcache/register_quiet 2>/dev/null || true > done > log_end_msg "bcache device scan complete" > else > log_warning_msg "/sys/fs/bcache/register_quiet not found; not registering devices" > fi -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
