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
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>> >> 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
>> >
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