RE: can't attach caching device to backing device

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I am running into the same issue with LVM, using the entire raid device, and using a single plain disk... I must be doing something wrong here.  I also tried deleting the writeback device's partition and just using the entire disk.

 ~ # pvcreate /dev/md127
  Physical volume "/dev/md127" successfully created

~ # vgcreate vg_500s_bcache /dev/md127
  Volume group "vg_500s_bcache" successfully created

~ # lvcreate -L50G -nlv_bcache_test vg_500s_bcache
  Logical volume "lv_bcache_test" created

 ~ # make-bcache -B /dev/vg_500s_bcache/lv_bcache_test
UUID:                   0847db15-4d6b-4271-a052-4338752a704f
Set UUID:               06fa14ab-cbbe-4e10-ac5c-f48f92ffea39
nbuckets:               102400
block_size:             8
bucket_size:            1024
nr_in_set:              1
nr_this_dev:            0
first_bucket:           1

 ~ # echo /dev/vg_500s_bcache/lv_bcache_test >/sys/fs/bcache/register
 ~ # echo /dev/sdk1 >/sys/fs/bcache/register

~ # echo "d5cadc1d-0fb6-4be5-bb32-f649c540c03d" >/sys/block/bcache0/bcache/attach
-bash: echo: write error: No such file or directory

Same issue with the device and no partitions:
~ # make-bcache -B /dev/md127
UUID:                   4c113d06-5724-45fa-900d-bead27233de9
Set UUID:               500a22f2-c35a-4031-b5f3-9bf865c941bf
nbuckets:               2861624
block_size:             8
bucket_size:            1024
nr_in_set:              1
nr_this_dev:            0
first_bucket:           1
~ # echo /dev/sdk1 >/sys/fs/bcache/register
 ~ # echo /dev/md127 >/sys/fs/bcache/register
 ~ # probe-bcache /dev/sdk1
d5cadc1d-0fb6-4be5-bb32-f649c540c03d: UUID="" TYPE="bcache"
 ~ # echo "d5cadc1d-0fb6-4be5-bb32-f649c540c03d" >/sys/block/md127/bcache/attach
-bash: echo: write error: No such file or directory

- Justin


-----Original Message-----
From: Justin Rush 
Sent: Monday, November 21, 2011 7:57 AM
To: 'Kent Overstreet'
Cc: kent.overstreet@xxxxxxxxx; linux-bcache@xxxxxxxxxxxxxxx
Subject: RE: can't attach caching device to backing device

Great, I'll try the new code when I get home since the end goal is to use LVM on top of the raid devices and then present the LVs (or /dev/bcach*) to tcm/lio.

If there is any debug information I can give you, please let me know.

- Justin


-----Original Message-----
From: Kent Overstreet [mailto:koverstreet@xxxxxxxxxx]
Sent: Monday, November 21, 2011 7:54 AM
To: Justin Rush
Cc: kent.overstreet@xxxxxxxxx; linux-bcache@xxxxxxxxxxxxxxx
Subject: Re: can't attach caching device to backing device

On Mon, Nov 21, 2011 at 01:51:00PM +0000, Justin Rush wrote:
> Yes, the file does exist.

Hmm. Weird. I'll look at the code and see if I can think of anything.

> Should I try it with the individual devices in the array?

Worth a shot, though caching partitions is well tested. 

> I don't suppose bcache can play with LVM?

The version I just pushed should now.
> 
> - Justin
> 
> -----Original Message-----
> From: Kent Overstreet [kent.overstreet@xxxxxxxxx]
> Received: Sunday, 20 Nov 2011, 11:31pm
> To: Justin Rush [jarush@xxxxxxxx]
> CC: linux-bcache@xxxxxxxxxxxxxxx [linux-bcache@xxxxxxxxxxxxxxx]
> Subject: Re: can't attach caching device to backing device When you 
> tried to attach the cache, did the file you were echoing to exist?
> That looks correct but I'm not sure what else would generate that 
> error.
> 
> For the UUIDs to show up in blkid, blkid itself would have to be 
> updated to know about the bcache superblock (IIRC it lives in 
> util-linux). I should probably ping the author and see if that can get 
> included.
> 
> If you have the udev rules and probe-bcache installed, the symlinks 
> /ought/ to show up when you reboot but I haven't tested that in ages.
> 
> I just got the code written so that it ought to be able to work on top 
> of md devices again, which means I should be able to run it at home 
> and I'll have to fix probe-bcache if it's broken then :)
> 
> On Mon, Nov 14, 2011 at 3:10 PM, Justin Rush <jarush@xxxxxxxx> wrote:
> > Using 3.1.0-rc9
> >
> > I created a cache device on /dev/sdk1 # ./make-bcache -C -b512k -w4k 
> > --writeback /dev/sdk1
> >
> > and a backing device on /dev/md127p1.
> > ./make-bcache -B /dev/md127p1
> >
> > # ./probe-bcache /dev/sdk1
> > 5f42bdd1-4342-4ab6-8dda-855989a09604: UUID="" TYPE="bcache"
> >
> > # ./probe-bcache /dev/md127p1
> > 6bbac9a4-afbd-4d40-9562-cdd290622c5d: UUID="" TYPE="bcache"
> >
> > I then registered them by:
> > # echo /dev/sdk1 >/sys/fs/bcache/register # echo /dev/md127p1
> > >/sys/fs/bcache/register
> >
> > I have /dev/bcache0
> >
> > When I try to attach the cache, I get this:
> > # echo "5f42bdd1-4342-4ab6-8dda-855989a09604" 
> > >/sys/block/md127/md127p1/bcache/attach
> > -bash: echo: write error: No such file or directory
> >
> > I believe this problem is due to the UUIDs for the two devices, but 
> > this is just a guess.  The UUID for /dev/sdk1 and /dev/md127p1 
> > doesn't appear to be registering properly as they don't show up in 
> > blkid.  I tried specifying the UUID to use with the -U option when 
> > creating the devices, but that didn't seem to help.  I do have the 
> > udev rules file from the tools in place
> >
> > Does anyone know what is going on here and how to fix it?
> >
> > Justin Rush
> > jarush@xxxxxxxx
> >
> >
> > --
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