[dm-devel] dm crypt: export sysfs of kcryptd workqueue - broken dmsetup reload

[Ignat Korchagin]

Hi,

Looks like a2b8b2d975673b1a50ab0bcce5d146b9335edfad broke the ability
to reload dm-crypt targets.

I usually used to enable additional flags like this on an existing
dm-crypt instance:

ignat at dev:~$ sudo dmsetup table --showkeys test | sed 's/$/ 2
no_read_workqueue no_write_workqueue/' | sudo dmsetup reload test

Now the command fails with below:

device-mapper: reload ioctl on test  failed: Cannot allocate memory
Command failed.

I also get this in the kernel log:

[   61.138067][ T2594] sysfs: cannot create duplicate filename
'/devices/virtual/workqueue/kcryptd-251:0'
[   61.139949][ T2594] CPU: 0 PID: 2594 Comm: dmsetup Not tainted 5.10.0+ #48
[   61.141176][ T2594] Hardware name: QEMU Standard PC (i440FX + PIIX,
1996), BIOS 0.0.0 02/06/2015
[   61.142726][ T2594] Call Trace:
[   61.143293][ T2594]  dump_stack+0x7d/0xa3
[   61.144030][ T2594]  sysfs_warn_dup.cold+0x17/0x24
[   61.144897][ T2594]  sysfs_create_dir_ns+0x1f3/0x270
[   61.145844][ T2594]  ? sysfs_create_mount_point+0x90/0x90
[   61.146830][ T2594]  ? _raw_spin_lock+0x81/0xd0
[   61.147674][ T2594]  kobject_add_internal+0x2a6/0x860
[   61.148594][ T2594]  ? table_load+0x2d7/0x690
[   61.149372][ T2594]  ? ctl_ioctl+0x3a1/0x950
[   61.150122][ T2594]  kobject_add+0x125/0x190
[   61.150914][ T2594]  ? kset_create_and_add+0x160/0x160
[   61.151812][ T2594]  ? unpoison_range+0x3a/0x60
[   61.152616][ T2594]  ? ____kasan_kmalloc.constprop.0+0x82/0xa0
[   61.153633][ T2594]  ? unpoison_range+0x3a/0x60
[   61.154459][ T2594]  device_add+0x2d7/0x1a40
[   61.155235][ T2594]  ? dev_set_name+0xb0/0xe0
[   61.156001][ T2594]  ? memset+0x20/0x40
[   61.156680][ T2594]  ? __fw_devlink_link_to_suppliers+0x560/0x560
[   61.157762][ T2594]  ? pm_runtime_init+0x2a3/0x380
[   61.158646][ T2594]  workqueue_sysfs_register+0x17e/0x370
[   61.159593][ T2594]  alloc_workqueue+0x559/0xb50
[   61.160401][ T2594]  ? workqueue_sysfs_register+0x370/0x370
[   61.161387][ T2594]  ? sscanf+0xab/0xe0
[   61.162063][ T2594]  ? bioset_init+0x41a/0x710
[   61.162870][ T2594]  crypt_ctr+0x24d5/0x2f90
[   61.163624][ T2594]  ? crypt_ctr_cipher_new.constprop.0+0xa30/0xa30
[   61.164703][ T2594]  ? realloc_argv+0xd2/0x110
[   61.165492][ T2594]  ? dm_table_destroy+0x410/0x410
[   61.166357][ T2594]  dm_table_add_target+0x45d/0xc40
[   61.167239][ T2594]  ? dm_table_create+0xd8/0x320
[   61.168090][ T2594]  ? dm_split_args+0x580/0x580
[   61.168910][ T2594]  ? __mutex_lock_slowpath+0x10/0x10
[   61.169800][ T2594]  ? dm_table_create+0x12b/0x320
[   61.170651][ T2594]  table_load+0x2d7/0x690
[   61.171395][ T2594]  ? __kasan_kmalloc_large+0x89/0xb0
[   61.172295][ T2594]  ? dev_suspend+0x4a0/0x4a0
[   61.173109][ T2594]  ? __kmalloc_node+0x275/0x320
[   61.173960][ T2594]  ? __might_fault+0x4f/0x70
[   61.174733][ T2594]  ctl_ioctl+0x3a1/0x950
[   61.175492][ T2594]  ? dev_suspend+0x4a0/0x4a0
[   61.176248][ T2594]  ? free_params+0x30/0x30
[   61.176968][ T2594]  dm_ctl_ioctl+0xa/0x10
[   61.177659][ T2594]  __x64_sys_ioctl+0x7ff/0x1110
[   61.178472][ T2594]  ? generic_block_fiemap+0x60/0x60
[   61.179308][ T2594]  do_syscall_64+0x33/0x40
[   61.180045][ T2594]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   61.181007][ T2594] RIP: 0033:0x7f48230e0427
[   61.181722][ T2594] Code: 00 00 90 48 8b 05 69 aa 0c 00 64 c7 00 26
00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10
00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 39 aa 0c 00 f7 d8
64 89 01 48
[   61.184908][ T2594] RSP: 002b:00007ffd1469cb68 EFLAGS: 00000202
ORIG_RAX: 0000000000000010
[   61.186262][ T2594] RAX: ffffffffffffffda RBX: 00007f48231bea7f
RCX: 00007f48230e0427
[   61.187590][ T2594] RDX: 0000556251e1dea0 RSI: 00000000c138fd09
RDI: 0000000000000003
[   61.188970][ T2594] RBP: 00007ffd1469cc20 R08: 00007f482320d310
R09: 00007ffd1469c9d0
[   61.190290][ T2594] R10: 00007f482320c65a R11: 0000000000000202
R12: 00007f482320c65a
[   61.191639][ T2594] R13: 00007f482320c65a R14: 00007f482320c65a
R15: 00007f482320c65a
[   61.193014][ T2594] kobject_add_internal failed for kcryptd-251:0
with -EEXIST, don't try to register things with the same name in the
same directory.
[   61.201542][ T2594] device-mapper: table: 251:0: crypt: Couldn't
create kcryptd queue
[   61.203050][ T2594] device-mapper: ioctl: error adding target to table

Seems we're missing a clean-up somewhere, so it tries to create multiple queues.

Regards,
Ignat