[linux-lvm] bcache and dm targets (specifically lvm)

Sat Mar 3 02:28:27 UTC 2012

Ahh!

I didn't know LVM had a device type lookup table. You can see if you
look further that it also reads new types from the lvm.conf file.
Adding this line to lvm.conf fixes the problem:

types = [ "bcache", 16 ]

I would imagine if merged it would be added to the internal compiled in table.

Thanks for the pointer.
Joseph.

On 3 March 2012 13:17, Kent Overstreet <koverstreet at google.com> wrote:
> I found the bug. Ugh...
>
> pvcreate refuses to use a device it doesn't recognize - look at the
> lvm2 source, lib/filters/filter.c
>
> I don't know why and I don't think I want to know. I imagine it'd work
> if you commented out the offending check (line 143 in my version).
>
> Maybe one of them can explain what's going on.
>
> On Fri, Mar 2, 2012 at 4:48 PM, Joseph Glanville
> <joseph.glanville at orionvm.com.au> wrote:
>> Cheers, I will try with a full disk device sometime later today.
>>
>> Thanks for you help,
>> Joseph.
>>
>> On 3 March 2012 11:01, Kent Overstreet <koverstreet at google.com> wrote:
>>> Strange, I don't see anything obvious in that log. Well, shouldn't be
>>> too hard to track down, I'll see if I can reproduce it.
>>>
>>> On Fri, Mar 2, 2012 at 2:37 PM, Joseph Glanville
>>> <joseph.glanville at orionvm.com.au> wrote:
>>>> Hi Kent,
>>>>
>>>> The block device did indeed get created in /dev and the correct
>>>> pointer exists in /sys/block/bcache0/dev
>>>> I straced pvcreate and attached the outout, I couldn't see anything
>>>> that far out of the ordinary though - bar the return that the device
>>>> had been filtered.
>>>> I am using commit f4c09286dd3f761310b24bc03e5ce95793a9a30c of
>>>> bcache-tools.git and commit 7c3e597ca0f5c87767548d1e9aced024aa558b2a
>>>> of linux-bcache.git
>>>>
>>>> The other thing I noticed was that the /dev/disk-by/uuid symlink
>>>> wasn't created. I went ahead and created this myself but I will
>>>> investigate why the udev rule didn't do this for me.
>>>>
>>>> Below is relevant lines from pvscan and pvcreate:
>>>>
>>>> dev05 ~ # cat pvscan.log | grep bcache
>>>> execve("/sbin/pvscan", ["pvscan", "/dev/bcache0"], [/* 23 vars */]) = 0
>>>> read(3, "strace\0pvscan\0/dev/bcache0\0", 31) = 27
>>>> readlink("/sys/class/block/bcache0",
>>>> "../../devices/virtual/block/bcache0"..., 1024) = 35
>>>> stat("/sys/devices/virtual/block/bcache0/uevent",
>>>> {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0
>>>> readlink("/sys/devices/virtual/block/bcache0", 0x7fff9e17aea0, 1024) =
>>>> -1 EINVAL (Invalid argument)
>>>> stat("/sys/devices/virtual/block/bcache0/uevent",
>>>> {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0
>>>> open("/sys/devices/virtual/block/bcache0/uevent", O_RDONLY|O_CLOEXEC) = 4
>>>> read(4, "MAJOR=252\nMINOR=0\nDEVNAME=bcache"..., 4096) = 47
>>>> readlink("/sys/devices/virtual/block/bcache0/subsystem",
>>>> "../../../../class/block"..., 1024) = 23
>>>> read(4, "N:bcache0\nW:40\nI:580433490\n", 4096) = 27
>>>> stat("/dev/bcache0", {st_mode=S_IFBLK|0660, st_rdev=makedev(252, 0), ...}) = 0
>>>> stat("/sys/class/block/bcache0/dev", {st_mode=S_IFREG|0444,
>>>> st_size=4096, ...}) = 0
>>>> open("/sys/class/block/bcache0/dev", O_RDONLY) = 6
>>>>
>>>> dev05 ~ # cat pvcreate-strace.log | grep bcache
>>>> execve("/sbin/pvcreate", ["pvcreate", "/dev/bcache0"], [/* 23 vars */]) = 0
>>>> read(3, "strace\0pvcreate\0/dev/bcache0\0", 31) = 29
>>>> stat("/dev/bcache0", {st_mode=S_IFBLK|0660, st_rdev=makedev(252, 0), ...}) = 0
>>>> readlink("/sys/dev/block/252:0",
>>>> "../../devices/virtual/block/bcache0", 1024) = 35
>>>> stat("/sys/devices/virtual/block/bcache0/uevent",
>>>> {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0
>>>> stat("/sys/class/block/bcache0/dev", {st_mode=S_IFREG|0444,
>>>> st_size=4096, ...}) = 0
>>>> open("/sys/class/block/bcache0/dev", O_RDONLY) = 6
>>>> stat("/dev/bcache0", {st_mode=S_IFBLK|0660, st_rdev=makedev(252, 0), ...}) = 0
>>>> stat("/dev/bcache0", {st_mode=S_IFBLK|0660, st_rdev=makedev(252, 0), ...}) = 0
>>>> stat("/sys/class/block/bcache0/dev", {st_mode=S_IFREG|0444,
>>>> st_size=4096, ...}) = 0
>>>> open("/sys/class/block/bcache0/dev", O_RDONLY) = 6
>>>> write(2, "Device /dev/bcache0 not found (o"..., 56Device /dev/bcache0
>>>> not found (or ignored by filtering).) = 56
>>>>
>>>> Kind regards,
>>>> Joseph.
>>>>
>>>>
>>>> On 2 March 2012 17:44, Kent Overstreet <kent.overstreet at gmail.com> wrote:
>>>>> Oh - try stracing the pvcreate and see what happens.
>>>>>
>>>>> On Thu, Mar 1, 2012 at 10:03 PM, Kent Overstreet
>>>>> <kent.overstreet at gmail.com> wrote:
>>>>>> Weird.
>>>>>>
>>>>>> Did the /dev/bcache0 device get create created by udev?
>>>>>>
>>>>>> It's possible my code isn't poking the right thing. *mutters about the
>>>>>> block layer...*
>>>>>>
>>>>>> On Thu, Mar 1, 2012 at 9:49 PM, Joseph Glanville
>>>>>> <joseph.glanville at orionvm.com.au> wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I can't use bcache devices as members of lvm volume groups because
>>>>>>> dmsetup can't find the devices.
>>>>>>> It provides the ever useful feedback of:
>>>>>>> # pvcreate /dev/bcache0
>>>>>>>   Device /dev/bcache0 not found (or ignored by filtering).
>>>>>>>
>>>>>>> My LVM.conf is only filtering out nbd devices:
>>>>>>> filter = [ "r|/dev/nbd.*|", "a/.*/" ]
>>>>>>>
>>>>>>> Any insight would be greatly appreciated. :)
>>>>>>>
>>>>>>> I also noted that bcache devices don't appear in iostat..
>>>>>>>
>>>>>>> Joseph.
>>>>>>>
>>>>>>> --
>>>>>>> Founder | Director | VP Research
>>>>>>> Orion Virtualisation Solutions | www.orionvm.com.au | Phone: 1300 56
>>>>>>> 99 52 | Mobile: 0428 754 846
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Founder | Director | VP Research
>>>>>>> Orion Virtualisation Solutions | www.orionvm.com.au | Phone: 1300 56
>>>>>>> 99 52 | Mobile: 0428 754 846
>>>>>>> --
>>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-bcache" in
>>>>>>> the body of a message to majordomo at vger.kernel.org
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>>>>
>>>>
>>>>
>>>> --
>>>> Founder | Director | VP Research
>>>> Orion Virtualisation Solutions | www.orionvm.com.au | Phone: 1300 56
>>>> 99 52 | Mobile: 0428 754 846
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-bcache" in
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>>
>>
>>
>> --
>> Founder | Director | VP Research
>> Orion Virtualisation Solutions | www.orionvm.com.au | Phone: 1300 56
>> 99 52 | Mobile: 0428 754 846

-- 
Founder | Director | VP Research
Orion Virtualisation Solutions | www.orionvm.com.au | Phone: 1300 56
99 52 | Mobile: 0428 754 846