September 2, 201411 yr I am getting this error in my syslog related to the BTRFS cache drive: kernel: BTRFS info (device sdd1): The free space cache file (26872905728) is invalid. skip it I'm currently on 6b8 but I've had the error since 6b6. In 6b6 it led to the "(28) No space left on device" error, but in betas 7 and 8 it hasn't caused any problems that I know of. I have already run the btrfs scrub option that was added to 6b7 but it didn't find or fix anything. From what I can tell, the BTRFS clear_cache mount option should take care of the problem: https://btrfs.wiki.kernel.org/index.php/Mount_options Would this be the right process to use that option? * Stop the array * unmount /mnt/cache * mount -t btrfs -o noatime,nodiratime,clear_cache /dev/sdd1 /mnt/cache * run htop, watch for btrfs-freespace to drop off the list * reboot Thanks for any advice! syslog-20140901.txt
September 2, 201411 yr I am getting this error in my syslog related to the BTRFS cache drive: kernel: BTRFS info (device sdd1): The free space cache file (26872905728) is invalid. skip it I'm currently on 6b8 but I've had the error since 6b6. In 6b6 it led to the "(28) No space left on device" error, but in betas 7 and 8 it hasn't caused any problems that I know of. I have already run the btrfs scrub option that was added to 6b7 but it didn't find or fix anything. From what I can tell, the BTRFS clear_cache mount option should take care of the problem: https://btrfs.wiki.kernel.org/index.php/Mount_options Well that's a new one for me - never seen that before. There is definitely a learning curve involved with btrfs. Would this be the right process to use that option? * Stop the array * unmount /mnt/cache * mount -t btrfs -o noatime,nodiratime,clear_cache /dev/sdd1 /mnt/cache * run htop, watch for btrfs-freespace to drop off the list * reboot Thanks for any advice! Once you Stop the array everything is un-mounted and all the mount points are removed. Try this: * Stop array * mkdir /x * mount -o clear_cache /dev/sdd1 /x [/dev/sdd is your cache volume] * run htop, watch for btrfs-freespace to drop off the list * reboot * report back here what happens
September 2, 201411 yr Author Thanks. Hmm, I'm not sure how long to wait before rebooting. I had assumed btrfs-freespace would show up in htop, but it doesn't. it doesn't really look like it is doing much: root@Tower:~# ps -ef | grep "btrfs-freespace" root 17662 2 0 18:25 ? 00:00:00 [btrfs-freespace] root 17752 17740 0 18:30 pts/0 00:00:00 grep btrfs-freespace Here's what the wiki says: clear_cache Clear all the free space caches during mount. This is a safe option, but will trigger rebuilding of the space cache, so leave the filesystem mounted for some time and let the rebuild process finish. If the process btrfs-freespace is actively doing some IO, it's probably not finished yet. This mount option is intended to be used one time and only after you notice some problems with free space. Any idea how to tell if it is "actively doing some IO"?
September 2, 201411 yr Author I went ahead and rebooted. Not sure if took 2 seconds or 20 minutes to fix but I'm not getting the error any more. Thanks!
February 15, 20242 yr Ran into this myself after this Raspberry Pi 5 bug caused my btrfs cluster to crash: https://github.com/raspberrypi/linux/issues/5753#issuecomment-1943553432 `nocache` fixed it and scrub was now able to be performed, thanks a bunch!
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