can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Scott McGillivray]

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

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

Re: can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Eric Wheeler]

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@vger.kernel.org
> 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

Re: can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Scott McGillivray]

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


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@ewheeler.net> 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@vger.kernel.org
>> 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
>

Re: can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Eric Wheeler]

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@ewheeler.net> 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@vger.kernel.org
> >> 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@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Scott McGillivray]

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@lists.ewheeler.net> 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@ewheeler.net> 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@vger.kernel.org
>> >> 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@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>

Re: can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Eric Wheeler]

On Thu, 25 Feb 2016, Scott McGillivray wrote:

> 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


Try this:
  make-bcache -w 4096 -C /dev/zram0

> 
> 
> On 25 February 2016 at 14:44, Eric Wheeler <bcache@lists.ewheeler.net> 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@ewheeler.net> 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@vger.kernel.org
> >> >> 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@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>
> 

Re: can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Eric Wheeler]

On Thu, 25 Feb 2016, Eric Wheeler wrote:

> On Thu, 25 Feb 2016, Scott McGillivray wrote:
> 
> > 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
> 
> 
> Try this:
>   make-bcache -w 4096 -C /dev/zram0

I'm not sure if -w needs to be called on the backing device too---but if 
you do then expect to loose data when reformatting.

If you decide reformat both backing and cache devices to test, then you 
might consider aligning your data to your backing volume's stride width 
with --data-offset NNN while you're at it if you haven't already.

-Eric

> 
> > 
> > 
> > On 25 February 2016 at 14:44, Eric Wheeler <bcache@lists.ewheeler.net> 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@ewheeler.net> 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@vger.kernel.org
> > >> >> 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@vger.kernel.org
> > >> 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@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Scott McGillivray]

yes thank you. When using zram and -w 4096 it worked as expected.

But when i re-tested with /dev/ram0 which is using the BLK_DEV_RAM/brd
ram device as cache. The make-bcache worked OK but when i tried to
register the device via "echo /dev/ram0 > /sys/fs/bcache/register" it
blows up with below error in dmesg.

Call Trace:
[ 8460.086681]  [<ffffffff812f8ae7>] kobj_attr_store+0xf/0x19
[ 8460.086685]  [<ffffffff811fd737>] sysfs_kf_write+0x3e/0x40
[ 8460.086689]  [<ffffffff811fcc40>] kernfs_fop_write+0xe9/0x136
[ 8460.086694]  [<ffffffff8119b0ed>] __vfs_write+0x28/0xa7
[ 8460.086699]  [<ffffffff81286ed3>] ? security_file_permission+0x3b/0x42
[ 8460.086705]  [<ffffffff8109b30c>] ? percpu_down_read+0x1f/0x41
[ 8460.086708]  [<ffffffff8119d604>] ? __sb_start_write+0x24/0x41
[ 8460.086712]  [<ffffffff8119bba2>] vfs_write+0x8f/0xe5
[ 8460.086715]  [<ffffffff8119c534>] SyS_write+0x46/0x79
[ 8460.086720]  [<ffffffff81645176>] entry_SYSCALL_64_fastpath+0x16/0x75
[ 8460.086722] Code: 00 48 83 ff 04 77 09 49 89 bd b8 0a 00 00 eb 0f
e8 c6 c3 ff ff 48 ff c8 49 89 85 b8 0a 00 00 49 8b bd b8 0a 00 00 48
85 ff 75 02 <0f> 0b 48 ff c7 e8 a6 c3 ff ff 48 8d 14 c5 00 00 00 00 48
ff c8
[ 8460.086766] RIP  [<ffffffffc00e832f>] register_bcache+0xe27/0x1423 [bcache]



On 25 February 2016 at 15:39, Eric Wheeler <bcache@lists.ewheeler.net> wrote:
> On Thu, 25 Feb 2016, Eric Wheeler wrote:
>
>> On Thu, 25 Feb 2016, Scott McGillivray wrote:
>>
>> > 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
>>
>>
>> Try this:
>>   make-bcache -w 4096 -C /dev/zram0
>
> I'm not sure if -w needs to be called on the backing device too---but if
> you do then expect to loose data when reformatting.
>
> If you decide reformat both backing and cache devices to test, then you
> might consider aligning your data to your backing volume's stride width
> with --data-offset NNN while you're at it if you haven't already.
>
> -Eric
>
>>
>> >
>> >
>> > On 25 February 2016 at 14:44, Eric Wheeler <bcache@lists.ewheeler.net> 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@ewheeler.net> 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@vger.kernel.org
>> > >> >> 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@vger.kernel.org
>> > >> 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@vger.kernel.org
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>>

Re: can't use ramdisk as cache device. Receive "Can't attach [UUID]: cache set not found" error

[Eric Wheeler]

On Thu, 25 Feb 2016, Scott McGillivray wrote:

> yes thank you. When using zram and -w 4096 it worked as expected.
> 
> But when i re-tested with /dev/ram0 which is using the BLK_DEV_RAM/brd
> ram device as cache. The make-bcache worked OK but when i tried to
> register the device via "echo /dev/ram0 > /sys/fs/bcache/register" it
> blows up with below error in dmesg.
> 
> Call Trace:
> [ 8460.086681]  [<ffffffff812f8ae7>] kobj_attr_store+0xf/0x19
> [ 8460.086685]  [<ffffffff811fd737>] sysfs_kf_write+0x3e/0x40
> [ 8460.086689]  [<ffffffff811fcc40>] kernfs_fop_write+0xe9/0x136
> [ 8460.086694]  [<ffffffff8119b0ed>] __vfs_write+0x28/0xa7
> [ 8460.086699]  [<ffffffff81286ed3>] ? security_file_permission+0x3b/0x42
> [ 8460.086705]  [<ffffffff8109b30c>] ? percpu_down_read+0x1f/0x41
> [ 8460.086708]  [<ffffffff8119d604>] ? __sb_start_write+0x24/0x41
> [ 8460.086712]  [<ffffffff8119bba2>] vfs_write+0x8f/0xe5
> [ 8460.086715]  [<ffffffff8119c534>] SyS_write+0x46/0x79
> [ 8460.086720]  [<ffffffff81645176>] entry_SYSCALL_64_fastpath+0x16/0x75
> [ 8460.086722] Code: 00 48 83 ff 04 77 09 49 89 bd b8 0a 00 00 eb 0f
> e8 c6 c3 ff ff 48 ff c8 49 89 85 b8 0a 00 00 49 8b bd b8 0a 00 00 48
> 85 ff 75 02 <0f> 0b 48 ff c7 e8 a6 c3 ff ff 48 8d 14 c5 00 00 00 00 48
> ff c8
> [ 8460.086766] RIP  [<ffffffffc00e832f>] register_bcache+0xe27/0x1423 [bcache]

I just posted a patch in the thread "Re: bcache: register_cache() error 
opening sdh2" that might cleanup register_cache() error handling, and 
might give a better error---but ram0 devices are rather old and might not 
do what you want.  I seem to remember they need to be initialized by 
	dd if=/dev/zero of=/dev/ram0 
or some such thing.  I always seem to have trouble with /dev/ramX devices.

You might be better off using /dev/loop0 and loopback a file in /dev/shm/ 
or /dev/hugepages/.


--
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


> 
> 
> 
> On 25 February 2016 at 15:39, Eric Wheeler <bcache@lists.ewheeler.net> wrote:
> > On Thu, 25 Feb 2016, Eric Wheeler wrote:
> >
> >> On Thu, 25 Feb 2016, Scott McGillivray wrote:
> >>
> >> > 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
> >>
> >>
> >> Try this:
> >>   make-bcache -w 4096 -C /dev/zram0
> >
> > I'm not sure if -w needs to be called on the backing device too---but if
> > you do then expect to loose data when reformatting.
> >
> > If you decide reformat both backing and cache devices to test, then you
> > might consider aligning your data to your backing volume's stride width
> > with --data-offset NNN while you're at it if you haven't already.
> >
> > -Eric
> >
> >>
> >> >
> >> >
> >> > On 25 February 2016 at 14:44, Eric Wheeler <bcache@lists.ewheeler.net> 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@ewheeler.net> 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@vger.kernel.org
> >> > >> >> 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@vger.kernel.org
> >> > >> 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@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>
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