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[Kick In <pierre-andre.morey@xxxxxxxxxxxxx>]

Public bug reported:

Hi,

I found a bug that crashes the machine if you create a bcache where the
caching device size is bigger than backing device.

This case may happen if you create a bcache with a plan to add a bigger
disk/partition/raid later to it.

To reproduce it follow this steps:

start a vm with utopic-amd64-desktop iso, it must have 2 disks, one of
16G and on of 8G

apt-get update && apt-get install bcache-tools
/dev/sda is 16G caching device
/dev/sdb is 8G backing device

make-bcache --write-back --discard -C /dev/sda -B /dev/sdb
now the machine is hanged.

if you reboot and reinstall bcache-tools
the bcache device has been created

************************************
bcache-super-show -f /dev/sda:
==============================
sb.magic		ok
sb.first_sector		8 [match]
sb.csum			45C96B38A79275A7 [match]
sb.version		0 [cache device]

dev.label		(empty)
dev.uuid		155ab65e-e74a-4ca8-91da-467ef696db63
dev.sectors_per_block	1
dev.sectors_per_bucket	1024
dev.cache.first_sector	1024
dev.cache.cache_sectors	33553408
dev.cache.total_sectors	33554432
dev.cache.ordered	no
dev.cache.discard	yes
dev.cache.pos		0
dev.cache.replacement	0 [lru]

cset.uuid               bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8

*****************************************************
bcache-super-show /dev/sdb:
=============================================
sb.magic		ok
sb.first_sector		8 [match]
sb.csum			F37A1BB08A7F5DE7 [match]
sb.version		1 [backing device]

dev.label		(empty)
dev.uuid		341f1c83-1797-4157-aa9e-524107db5606
dev.sectors_per_block	1
dev.sectors_per_bucket	1024
dev.data.first_sector	16
dev.data.cache_mode	1 [writeback]
dev.data.cache_state	0 [detached]

cset.uuid		bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8
*****************************************************

you can format it:
mkfs.ext4 /dev/bcache0
Rejet des blocs de périphérique : complété
Creating filesystem with 2097150 4k blocks and 524288 inodes
Filesystem UUID: b99a09de-3a92-4a44-82cd-29f75f8bf0c9
Superblocs de secours stockés sur les blocs :
 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Allocation des tables de groupe : complété
Écriture des tables d'i-noeuds : complété
Création du journal (32768 blocs) : complété
Écriture des superblocs et de l'information de comptabilité du système de
fichiers :

restarting the format gave me an other bug (X.org crashing):
free from cli:
             total       used       free     shared    buffers     cached
Mem:       1017168     814040     203128     195568      91264     513064
-/+ buffers/cache:     209712     807456
Swap:            0          0          0

tail /var/log/syslog:
[  568.016481] [ 4983]     0  4983     3332      121      11        0             0 mdadm
[  568.016483] [ 5259]     0  5259     6703      300      19        0             0 mkfs.ext4
[  568.016484] Out of memory: Kill process 1947 (Xorg) score 38 or sacrifice child
[  568.016485] Killed process 1947 (Xorg) total-vm:313160kB, anon-rss:35976kB, file-rss:4232kB
[  568.707107] systemd-logind[1396]: Failed to start unit user@112.service: Unknown unit: user@112.service
[  568.707113] systemd-logind[1396]: Failed to start user service: Unknown unit: user@112.service
[  568.709876] systemd-logind[1396]: New session c8 of user lightdm.
[  568.709890] systemd-logind[1396]: Linked /tmp/.X11-unix/X0 to /run/user/112/X11-display.

You can unregister the bcache device:
[  830.811150] bcache: cached_dev_detach_finish() Caching disabled for sdb
[  830.949898] bcache: cache_set_free() Cache set bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8 unregistered

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

** Description changed:

  Hi,
  
  I found a bug that crashes the machine if you create a bcache where the
- cahcing device size is bigger than backing device.
+ caching device size is bigger than backing device.
+ 
+ This case may happen if you create a bcache with a plan to add a bigger
+ disk/partition/raid later to it.
  
  To reproduce it follow this steps:
  
  start a vm with utopic-amd64-desktop iso, it must have 2 disks, one of
  16G and on of 8G
  
  apt-get update && apt-get install bcache-tools
  /dev/sda is 16G caching device
  /dev/sdb is 8G backing device
  
  make-bcache --write-back --discard -C /dev/sda -B /dev/sdb
  now the machine is hanged.
  
- if you reboot and reinstall bcache-tools 
+ if you reboot and reinstall bcache-tools
  the bcache device has been created
  
  ************************************
  bcache-super-show -f /dev/sda:
  ==============================
  sb.magic		ok
  sb.first_sector		8 [match]
  sb.csum			45C96B38A79275A7 [match]
  sb.version		0 [cache device]
  
  dev.label		(empty)
  dev.uuid		155ab65e-e74a-4ca8-91da-467ef696db63
  dev.sectors_per_block	1
  dev.sectors_per_bucket	1024
  dev.cache.first_sector	1024
  dev.cache.cache_sectors	33553408
  dev.cache.total_sectors	33554432
  dev.cache.ordered	no
  dev.cache.discard	yes
  dev.cache.pos		0
  dev.cache.replacement	0 [lru]
  
  cset.uuid               bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8
  
  *****************************************************
  bcache-super-show /dev/sdb:
  =============================================
  sb.magic		ok
  sb.first_sector		8 [match]
  sb.csum			F37A1BB08A7F5DE7 [match]
  sb.version		1 [backing device]
  
  dev.label		(empty)
  dev.uuid		341f1c83-1797-4157-aa9e-524107db5606
  dev.sectors_per_block	1
  dev.sectors_per_bucket	1024
  dev.data.first_sector	16
  dev.data.cache_mode	1 [writeback]
  dev.data.cache_state	0 [detached]
  
  cset.uuid		bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8
  *****************************************************
  
  you can format it:
  mkfs.ext4 /dev/bcache0
- Rejet des blocs de périphérique : complété                        
+ Rejet des blocs de périphérique : complété
  Creating filesystem with 2097150 4k blocks and 524288 inodes
  Filesystem UUID: b99a09de-3a92-4a44-82cd-29f75f8bf0c9
- Superblocs de secours stockés sur les blocs : 
- 	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
+ Superblocs de secours stockés sur les blocs :
+  32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
  
- Allocation des tables de groupe : complété                        
- Écriture des tables d'i-noeuds : complété                        
+ Allocation des tables de groupe : complété
+ Écriture des tables d'i-noeuds : complété
  Création du journal (32768 blocs) : complété
  Écriture des superblocs et de l'information de comptabilité du système de
  fichiers :
  
  restarting the format gave me an other bug (X.org crashing):
  free from cli:
-              total       used       free     shared    buffers     cached
+              total       used       free     shared    buffers     cached
  Mem:       1017168     814040     203128     195568      91264     513064
  -/+ buffers/cache:     209712     807456
  Swap:            0          0          0
  
  tail /var/log/syslog:
  [  568.016481] [ 4983]     0  4983     3332      121      11        0             0 mdadm
  [  568.016483] [ 5259]     0  5259     6703      300      19        0             0 mkfs.ext4
  [  568.016484] Out of memory: Kill process 1947 (Xorg) score 38 or sacrifice child
  [  568.016485] Killed process 1947 (Xorg) total-vm:313160kB, anon-rss:35976kB, file-rss:4232kB
  [  568.707107] systemd-logind[1396]: Failed to start unit user@112.service: Unknown unit: user@112.service
  [  568.707113] systemd-logind[1396]: Failed to start user service: Unknown unit: user@112.service
  [  568.709876] systemd-logind[1396]: New session c8 of user lightdm.
  [  568.709890] systemd-logind[1396]: Linked /tmp/.X11-unix/X0 to /run/user/112/X11-display.
  
  You can unregister the bcache device:
  [  830.811150] bcache: cached_dev_detach_finish() Caching disabled for sdb
  [  830.949898] bcache: cache_set_free() Cache set bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8 unregistered

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https://bugs.launchpad.net/bugs/1377130

Title:
  Crash at creation of bcache if caching size > backing size

Status in “linux” package in Ubuntu:
  New

Bug description:
  Hi,

  I found a bug that crashes the machine if you create a bcache where
  the caching device size is bigger than backing device.

  This case may happen if you create a bcache with a plan to add a
  bigger disk/partition/raid later to it.

  To reproduce it follow this steps:

  start a vm with utopic-amd64-desktop iso, it must have 2 disks, one of
  16G and on of 8G

  apt-get update && apt-get install bcache-tools
  /dev/sda is 16G caching device
  /dev/sdb is 8G backing device

  make-bcache --write-back --discard -C /dev/sda -B /dev/sdb
  now the machine is hanged.

  if you reboot and reinstall bcache-tools
  the bcache device has been created

  ************************************
  bcache-super-show -f /dev/sda:
  ==============================
  sb.magic		ok
  sb.first_sector		8 [match]
  sb.csum			45C96B38A79275A7 [match]
  sb.version		0 [cache device]

  dev.label		(empty)
  dev.uuid		155ab65e-e74a-4ca8-91da-467ef696db63
  dev.sectors_per_block	1
  dev.sectors_per_bucket	1024
  dev.cache.first_sector	1024
  dev.cache.cache_sectors	33553408
  dev.cache.total_sectors	33554432
  dev.cache.ordered	no
  dev.cache.discard	yes
  dev.cache.pos		0
  dev.cache.replacement	0 [lru]

  cset.uuid               bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8

  *****************************************************
  bcache-super-show /dev/sdb:
  =============================================
  sb.magic		ok
  sb.first_sector		8 [match]
  sb.csum			F37A1BB08A7F5DE7 [match]
  sb.version		1 [backing device]

  dev.label		(empty)
  dev.uuid		341f1c83-1797-4157-aa9e-524107db5606
  dev.sectors_per_block	1
  dev.sectors_per_bucket	1024
  dev.data.first_sector	16
  dev.data.cache_mode	1 [writeback]
  dev.data.cache_state	0 [detached]

  cset.uuid		bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8
  *****************************************************

  you can format it:
  mkfs.ext4 /dev/bcache0
  Rejet des blocs de périphérique : complété
  Creating filesystem with 2097150 4k blocks and 524288 inodes
  Filesystem UUID: b99a09de-3a92-4a44-82cd-29f75f8bf0c9
  Superblocs de secours stockés sur les blocs :
   32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

  Allocation des tables de groupe : complété
  Écriture des tables d'i-noeuds : complété
  Création du journal (32768 blocs) : complété
  Écriture des superblocs et de l'information de comptabilité du système de
  fichiers :

  restarting the format gave me an other bug (X.org crashing):
  free from cli:
               total       used       free     shared    buffers     cached
  Mem:       1017168     814040     203128     195568      91264     513064
  -/+ buffers/cache:     209712     807456
  Swap:            0          0          0

  tail /var/log/syslog:
  [  568.016481] [ 4983]     0  4983     3332      121      11        0             0 mdadm
  [  568.016483] [ 5259]     0  5259     6703      300      19        0             0 mkfs.ext4
  [  568.016484] Out of memory: Kill process 1947 (Xorg) score 38 or sacrifice child
  [  568.016485] Killed process 1947 (Xorg) total-vm:313160kB, anon-rss:35976kB, file-rss:4232kB
  [  568.707107] systemd-logind[1396]: Failed to start unit user@112.service: Unknown unit: user@112.service
  [  568.707113] systemd-logind[1396]: Failed to start user service: Unknown unit: user@112.service
  [  568.709876] systemd-logind[1396]: New session c8 of user lightdm.
  [  568.709890] systemd-logind[1396]: Linked /tmp/.X11-unix/X0 to /run/user/112/X11-display.

  You can unregister the bcache device:
  [  830.811150] bcache: cached_dev_detach_finish() Caching disabled for sdb
  [  830.949898] bcache: cache_set_free() Cache set bcaa2595-bbc8-43a7-8c44-5d0aca0f3fc8 unregistered

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