that doesn't work either. It gives the same error from my opening post. Although this time it's also giving a new message in dmesg about block size. bcache: bch_cached_dev_attach() Couldn't attach sdf: block size less than set's block size bcache: __cached_dev_store() Can't attach 0bba8852-ad4f-41f4-bfa3-679a886a14ad : cache set not found which is strange because both devices block size are the same $ blockdev --getbsz /dev/sdf 4096 $ blockdev --getbsz /dev/zram0 4096 On 25 February 2016 at 14:44, Eric Wheeler <bcache@xxxxxxxxxxxxxxxxxx> wrote: > On Thu, 25 Feb 2016, Scott McGillivray wrote: > >> No, doesn't' work either i'm afraid. Below is example of failing >> silently with ram disk and succeeded with HDD as cache device. >> >> Tested with /lib/modules/4.5.0-rc3+/kernel/drivers/md/bcache/bcache.ko >> >> >> with zram - doesn't work >> ================= >> >> $ ls -al /sys/fs/bcache/ >> total 0 >> drwxr-xr-x 2 root root 0 Feb 25 13:42 . >> drwxr-xr-x 9 root root 0 Feb 25 13:40 .. >> --w------- 1 root root 4096 Feb 25 13:40 register >> --w------- 1 root root 4096 Feb 25 13:40 register_quiet >> >> $ file /dev/zram0 >> /dev/zram0: block special (250/0) >> >> $ fdisk -l /dev/zram0 >> Disk /dev/zram0: 1 GiB, 1073741824 bytes, 262144 sectors >> >> $ make-bcache -C /dev/zram0 >> UUID: 87e63981-7bd8-4cc3-93db-9ca275367c21 >> Set UUID: 0bba8852-ad4f-41f4-bfa3-679a886a14ad >> version: 0 >> nbuckets: 2048 >> block_size: 8 >> bucket_size: 1024 >> nr_in_set: 1 >> nr_this_dev: 0 >> first_bucket: 1 > > did you `echo /dev/zram0 > /sys/fs/bcache/register` > and then `echo <CSET-UUID> > /sys/block/bcache0/bcache/attach` > > Not sure which UUID is the CSET UUID. Probably > 0bba8852-ad4f-41f4-bfa3-679a886a14ad. > > See attaching bcache0 to a cache: > https://www.kernel.org/doc/Documentation/bcache.txt > > -Eric > >> >> >> No errors, but nothing in dmesg and contents of /sys/fs/bcache/ remain >> exactly the same... no UUID. Seems to just silently fail. >> >> >> with HDD - works as expected. >> ===================== >> >> $ fdisk -l /dev/sdf >> Disk /dev/sdf: 1 GiB, 1073741824 bytes, 2097152 sectors >> >> $ file /dev/sdf >> /dev/sdf: block special (8/80) >> >> $ make-bcache -C /dev/sdf >> UUID: 3234c9e7-8186-4a7c-99a8-ae6a371c6f2c >> Set UUID: 9a71faf7-a408-4f4d-906e-e5d67e43291f >> version: 0 >> nbuckets: 2048 >> block_size: 1 >> bucket_size: 1024 >> nr_in_set: 1 >> nr_this_dev: 0 >> first_bucket: 1 >> >> $ ls -al /sys/fs/bcache/ >> total 0 >> drwxr-xr-x 3 root root 0 Feb 25 13:48 . >> drwxr-xr-x 9 root root 0 Feb 25 13:40 .. >> drwxr-xr-x 7 root root 0 Feb 25 13:48 9a71faf7-a408-4f4d-906e-e5d67e43291f >> --w------- 1 root root 4096 Feb 25 13:40 register >> --w------- 1 root root 4096 Feb 25 13:40 register_quiet >> >> $ dmesg >> [ 714.168488] bcache: register_cache() registered cache device sdf >> >> >> Thank you. >> >> On 24 February 2016 at 15:37, Eric Wheeler <lists@xxxxxxxxxxxx> wrote: >> > >> > On Tue, 16 Feb 2016, Scott McGillivray wrote: >> > >> >> Hello >> >> >> >> I am using Ubuntu 15.10 with latest nightly 4.5 kernel. Ubuntu creates >> >> 16 RAM drives as /dev/ram0 - ram16 by default and i am trying to test >> >> bcache and use one of these as a cache device. >> >> >> >> wipefs /dev/sdd >> >> wipefs /dev/sdd -a >> >> wipefs /dev/ram0 >> >> wipefs /dev/ram0 -a >> >> make-bcache -B /dev/sdd -C /dev/ram0 >> > >> > Does it work with /dev/zram0? You would prep it something like this: >> > >> > modprobe zram >> > echo $((1024*1024*1024)) > /sys/block/zram0/disksize # 1GB >> > make-bcache -C /dev/zram0 >> > >> > -Eric >> > >> > >> > >> >> At this point there were no errors output but there is also no UUID >> >> entry in /sys/fs/bcache/. Only register and register_quiet. >> >> >> >> bache-super-show correctly prints info about both block and cache >> >> devices when queried but when i try to manually attach the cache >> >> device with echo cset.uuid > /sys/block/bcache0/bcache/attach i get no >> >> error but in dmesg i see >> >> >> >> bcache: __cached_dev_store() Can't attach >> >> 3f2521a6-2103-4e2e-a47d-cc56558e8f7d: cache set not found >> >> >> >> If i repeat this example but use another sd block device as cache then >> >> it works OK. >> >> >> >> Can anyone confirm if it should be possible to use the ramdisk based >> >> block device as a caching device with bcache ? >> >> >> >> I also tried to use a loop device as cache and that didn't work >> >> either.. i got "kernel bug" in dmesg for >> >> drivers/md/bcache/super.c:1812. RIP [] >> >> cache_alloc.isra.21+0x646/0x670[bcache] >> >> >> >> Does bcache need the cache device to be a certain block type i.e sd 8 >> >> ? Should i be able to use any block device from /proc/devices as a >> >> cache device ? >> >> >> >> The kernel options used for ramdisk are: >> >> >> >> CONFIG_BLK_DEV_RAM=y >> >> CONFIG_BLK_DEV_RAM_COUNT=16 >> >> CONFIG_BLK_DEV_RAM_SIZE=65536 >> >> CONFIG_BLK_DEV_RAM_DAX=y >> >> >> >> Thank you. >> >> Scott >> >> -- >> >> 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 >> >> >> > >> > >> > >> > -- >> > Eric Wheeler, President eWheeler, Inc. dba Global Linux Security >> > 888-LINUX26 (888-546-8926) Fax: 503-716-3878 PO Box 25107 >> > www.GlobalLinuxSecurity.pro Linux since 1996! Portland, OR 97298 >> > >> -- >> 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 >> -- 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