Re: make-bcache -B /dev/bcache0 fails, Can't stack bcache on top of bcache

[Dongsheng Yang <dongsheng.yang@easystack.cn>]

Hi Cedric,

     I have a patch to support overlay bcache, you can find it in branch:

https://github.com/yangdongsheng/linux/commits/bcache_writeback

     "bcache: support overlay bcache "

https://github.com/yangdongsheng/linux/commit/c72756df2d08acbb58565135bbde61134fb3208a

     You can give it a try.


Thanx


在 2021/1/3 星期日 上午 3:38, Cedric.dewijs@eclipso.eu 写道:
> ­I can't stack bcache on top of bcache, This command fails:
> # make-bcache -B /dev/bcache0
> Name			/dev/bcache0
> Label			
> Type			data
> UUID:			758be840-f232-44dd-8e56-83fb55ba20ea
> Set UUID:		ddbcc87b-d25d-483f-8874-49b80ba26472
> version:		1
> block_size_in_sectors:	1
> data_offset_in_sectors:	16
> [ 5187.054662] sysfs: cannot create duplicate filename '/devices/virtual/block/bcache0/bcache'
> [ 5187.054667] CPU: 2 PID: 567 Comm: bcache-register Not tainted 5.9.14-arch1-1 #1
> [ 5187.054669] Hardware name: Hewlett-Packard HP Compaq 8200 Elite CMT PC/1494, BIOS J01 v02.28 03/24/2015
> [ 5187.054670] Call Trace:
> [ 5187.054681]  dump_stack+0x6b/0x83
> [ 5187.054686]  sysfs_warn_dup.cold+0x17/0x24
> [ 5187.054694]  sysfs_create_dir_ns+0xc6/0xe0
> [ 5187.054699]  kobject_add_internal+0xab/0x2f0
> [ 5187.054703]  kobject_add+0x98/0xd0
> [ 5187.054707]  ? blk_queue_write_cache+0x2f/0x60
> [ 5187.054723]  register_bdev+0x337/0x360 [bcache]
> [ 5187.054735]  register_bcache+0x43c/0x910 [bcache]
> [ 5187.054740]  ? kernfs_fop_write+0xce/0x1b0
> [ 5187.054750]  ? register_cache+0x1290/0x1290 [bcache]
> [ 5187.054753]  kernfs_fop_write+0xce/0x1b0
> [ 5187.054756]  vfs_write+0xc7/0x210
> [ 5187.054759]  ksys_write+0x67/0xe0
> [ 5187.054763]  do_syscall_64+0x33/0x40
> [ 5187.054766]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 5187.054769] RIP: 0033:0x7fbd1edb3f67
> [ 5187.054772] Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
> [ 5187.054774] RSP: 002b:00007fff335fa418 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> [ 5187.054777] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007fbd1edb3f67
> [ 5187.054778] RDX: 000000000000000d RSI: 0000562bf3f902a0 RDI: 0000000000000003
> [ 5187.054780] RBP: 0000562bf3f902a0 R08: 00007fbd1ee4a040 R09: 00007fbd1ee4a0c0
> [ 5187.054781] R10: 00007fbd1ee49fc0 R11: 0000000000000246 R12: 000000000000000d
> [ 5187.054782] R13: 00007fff335fa4a0 R14: 000000000000000d R15: 00007fbd1ee86720
> [ 5187.054787] kobject_add_internal failed for bcache with -EEXIST, don't try to register things with the same name in the same directory.
> [ 5187.054789] bcache: register_bdev() error bcache0: error creating kobject
> [ 5187.054794] bcache: register_bcache() error : failed to register device
> [ 5187.054963] bcache: bcache_device_free() bcache3 stopped
>
> I expected this command to create a new /dev/bcacheX node. Instead it tries to overwrite /devices/virtual/block/bcache0/bcache
>
> My versions:
> # uname -a
> Linux bcache-test 5.9.14-arch1-1 #1 SMP PREEMPT Sat, 12 Dec 2020 14:37:12 +0000 x86_64 GNU/Linux
> # pacman -Q bcache-tools
> bcache-tools 1.1-1
>
> I've used this guide for inspiration:
> https://wiki.archlinux.org/index.php/Bcache
>
>
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