brd module compiled as built-in

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1593293

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

It looks like CONFIG_BLK_DEV_RAM was built in going as back as far as Trusty (14.04). Was there a prior release where you did not experience this bug?

Hello.

I never used brd on Trusty, all my previous experience with it was on Debian/Centos (they both have brd as 'm').

I've checked - even precise have it as 'y' - this make Ubuntu very different compare to all other distributions.

Main problem is that 'y' makes brd 'OS only' because it size fixed. And it makes impossible to free used by ramdisk memory by unloading module.

I have the problem too on ubuntu 16.04.

To reproduce:

sudo lsmod | grep brd :
(nothing) : it is builtin

sudo modprobe brd rd_size=123456

sudo mkfs.ext4 /dev/ram0

sudo mount /dev/ram0 /var/cache/ramdisk/

df -m | grep ramdisk :

/dev/ram0 58 2 53 3% /var/cache/ramdisk

 -> useless

Regards.

Yes, please please please change this to "m" -- making this built-in was a terrible idea.

https://lists.ubuntu.com/archives/kernel-team/2017-February/082294.html

https://lists.ubuntu.com/archives/kernel-team/2017-February/082295.html

This used to work on the last LTS. I reached for it today on Xenial and found it was broken. Now I can't do scale block device testing without rebooting the system.

This bug was fixed in the package linux - 4.10.0-8.10

---------------
linux (4.10.0-8.10) zesty; urgency=low

  [ Tim Gardner ]

  * Release Tracking Bug
    - LP: #1664217

  * [Hyper-V] Bug fixes for storvsc (tagged queuing, error conditions)
    (LP: #1663687)
    - scsi: storvsc: Enable tracking of queue depth
    - scsi: storvsc: Remove the restriction on max segment size
    - scsi: storvsc: Enable multi-queue support
    - scsi: storvsc: use tagged SRB requests if supported by the device
    - scsi: storvsc: properly handle SRB_ERROR when sense message is present
    - scsi: storvsc: properly set residual data length on errors

  * Ubuntu16.10-KVM:Big configuration with multiple guests running SRIOV VFs
    caused KVM host hung and all KVM guests down. (LP: #1651248)
    - KVM: PPC: Book 3S: XICS cleanup: remove XICS_RM_REJECT
    - KVM: PPC: Book 3S: XICS: correct the real mode ICP rejecting counter
    - KVM: PPC: Book 3S: XICS: Fix potential issue with duplicate IRQ resends
    - KVM: PPC: Book 3S: XICS: Implement ICS P/Q states
    - KVM: PPC: Book 3S: XICS: Don't lock twice when checking for resend

  * overlay: mkdir fails if directory exists in lowerdir in a user namespace
    (LP: #1531747)
    - SAUCE: overlayfs: Skip permission checking for trusted.overlayfs.* xattrs

  * CVE-2016-1575 (LP: #1534961)
    - SAUCE: overlayfs: Skip permission checking for trusted.overlayfs.* xattrs

  * CVE-2016-1576 (LP: #1535150)
    - SAUCE: overlayfs: Skip permission checking for trusted.overlayfs.* xattrs

  * Miscellaneous Ubuntu changes
    - SAUCE: md/raid6 algorithms: scale test duration for speedier boots
    - SAUCE: Import aufs driver
    - d-i: Build message-modules udeb for arm64
    - rebase to v4.10-rc8

  * Miscellaneous upstream changes
    - Revert "UBUNTU: SAUCE: aufs -- remove .readlink assignment"
    - Revert "UBUNTU: SAUCE: (no-up) aufs: for v4.9-rc1, support setattr_prepare()"
    - Revert "UBUNTU: SAUCE: aufs -- Add flags argument to aufs_rename()"
    - Revert "UBUNTU: SAUCE: aufs -- Convert to use xattr handlers"
    - Revert "UBUNTU: SAUCE: Import aufs driver"

  [ Upstream Kernel Changes ]

  * rebase to v4.10-rc8

 -- Tim Gardner <email address hidden> Mon, 06 Feb 2017 08:34:24 -0700

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-xenial' to 'verification-done-xenial'. If the problem still exists, change the tag 'verification-needed-xenial' to 'verification-failed-xenial'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-yakkety' to 'verification-done-yakkety'. If the problem still exists, change the tag 'verification-needed-yakkety' to 'verification-failed-yakkety'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

I can confirm that now I can/load remove module brd in 4.10.0-8-generic (zesty).

This bug was fixed in the package linux - 4.8.0-40.43

---------------
linux (4.8.0-40.43) yakkety; urgency=low

  * linux: 4.8.0-40.43 -proposed tracker (LP: #1667066)

  [ Andy Whitcroft ]
  * NFS client : permission denied when trying to access subshare, since kernel
    4.4.0-31 (LP: #1649292)
    - fs: Better permission checking for submounts

  * shaking screen (LP: #1651981)
    - drm/radeon: drop verde dpm quirks

  * [0bda:0328] Card reader failed after S3 (LP: #1664809)
    - usb: hub: Wait for connection to be reestablished after port reset

  * linux-lts-xenial 4.4.0-63.84~14.04.2 ADT test failure with linux-lts-xenial
    4.4.0-63.84~14.04.2 (LP: #1664912)
    - SAUCE: apparmor: fix link auditing failure due to, uninitialized var

  * In Ubuntu 17.04 : after reboot getting message in console like Unable to
    open file: /etc/keys/x509_ima.der (-2) (LP: #1656908)
    - SAUCE: ima: Downgrade error to warning

  * 16.04.2: Extra patches for POWER9 (LP: #1664564)
    - powerpc/mm: Fix no execute fault handling on pre-POWER5
    - powerpc/mm: Fix spurrious segfaults on radix with autonuma

  * ibmvscsis: Add SGL LIMIT (LP: #1662551)
    - ibmvscsis: Add SGL limit

  * [Hyper-V] Bug fixes for storvsc (tagged queuing, error conditions)
    (LP: #1663687)
    - scsi: storvsc: Enable tracking of queue depth
    - scsi: storvsc: Remove the restriction on max segment size
    - scsi: storvsc: Enable multi-queue support
    - scsi: storvsc: use tagged SRB requests if supported by the device
    - scsi: storvsc: properly handle SRB_ERROR when sense message is present
    - scsi: storvsc: properly set residual data length on errors

  * Ubuntu16.10-KVM:Big configuration with multiple guests running SRIOV VFs
    caused KVM host hung and all KVM guests down. (LP: #1651248)
    - KVM: PPC: Book 3S: XICS cleanup: remove XICS_RM_REJECT
    - KVM: PPC: Book 3S: XICS: correct the real mode ICP rejecting counter
    - KVM: PPC: Book 3S: XICS: Fix potential issue with duplicate IRQ resends
    - KVM: PPC: Book 3S: XICS: Implement ICS P/Q states
    - KVM: PPC: Book 3S: XICS: Don't lock twice when checking for resend

  * ISST-LTE:pNV: ppc64_cpu command is hung w HDs, SSDs and NVMe (LP: #1662666)
    - blk-mq: Avoid memory reclaim when remapping queues
    - blk-mq: Fix failed allocation path when mapping queues
    - blk-mq: Always schedule hctx->next_cpu

  * systemd-udevd hung in blk_mq_freeze_queue_wait testing unpartitioned NVMe
    drive (LP: #1662673)
    - percpu-refcount: fix reference leak during percpu-atomic transition

  * [Yakkety SRU] Enable KEXEC support in ARM64 kernel (LP: #1662554)
    - [Config] Enable KEXEC support in ARM64.

  * [Hyper-V] Fix ring buffer handling to avoid host throttling (LP: #1661430)
    - Drivers: hv: vmbus: On write cleanup the logic to interrupt the host
    - Drivers: hv: vmbus: On the read path cleanup the logic to interrupt the host
    - Drivers: hv: vmbus: finally fix hv_need_to_signal_on_read()

  * brd module compiled as built-in (LP: #1593293)
    - CONFIG_BLK_DEV_RAM=m

  * regession tests failing after stackprofile test is run (LP: #1661030)
    - SAUCE: fix regression with domain change in compla...

This bug was fixed in the package linux - 4.4.0-65.86

---------------
linux (4.4.0-65.86) xenial; urgency=low

  * linux: 4.4.0-65.86 -proposed tracker (LP: #1667052)

  [ Stefan Bader ]
  * Upgrade Redpine RS9113 driver to support AP mode (LP: #1665211)
    - SAUCE: Redpine driver to support Host AP mode

  * NFS client : permission denied when trying to access subshare, since kernel
    4.4.0-31 (LP: #1649292)
    - fs: Better permission checking for submounts

  * [Hyper-V] SAUCE: pci-hyperv fixes for SR-IOV on Azure (LP: #1665097)
    - SAUCE: PCI: hv: Fix wslot_to_devfn() to fix warnings on device removal
    - SAUCE: pci-hyperv: properly handle pci bus remove
    - SAUCE: pci-hyperv: lock pci bus on device eject

  * [Hyper-V/Azure] Please include Mellanox OFED drivers in Azure kernel and
    image (LP: #1650058)
    - net/mlx4_en: Fix bad WQE issue
    - net/mlx4_core: Fix racy CQ (Completion Queue) free
    - net/mlx4_core: Fix when to save some qp context flags for dynamic VST to VGT
      transitions
    - net/mlx4_core: Avoid command timeouts during VF driver device shutdown

  * Xenial update to v4.4.49 stable release (LP: #1664960)
    - ARC: [arcompact] brown paper bag bug in unaligned access delay slot fixup
    - selinux: fix off-by-one in setprocattr
    - Revert "x86/ioapic: Restore IO-APIC irq_chip retrigger callback"
    - cpumask: use nr_cpumask_bits for parsing functions
    - hns: avoid stack overflow with CONFIG_KASAN
    - ARM: 8643/3: arm/ptrace: Preserve previous registers for short regset write
    - target: Don't BUG_ON during NodeACL dynamic -> explicit conversion
    - target: Use correct SCSI status during EXTENDED_COPY exception
    - target: Fix early transport_generic_handle_tmr abort scenario
    - target: Fix COMPARE_AND_WRITE ref leak for non GOOD status
    - ARM: 8642/1: LPAE: catch pending imprecise abort on unmask
    - mac80211: Fix adding of mesh vendor IEs
    - netvsc: Set maximum GSO size in the right place
    - scsi: zfcp: fix use-after-free by not tracing WKA port open/close on failed
      send
    - scsi: aacraid: Fix INTx/MSI-x issue with older controllers
    - scsi: mpt3sas: disable ASPM for MPI2 controllers
    - xen-netfront: Delete rx_refill_timer in xennet_disconnect_backend()
    - ALSA: seq: Fix race at creating a queue
    - ALSA: seq: Don't handle loop timeout at snd_seq_pool_done()
    - drm/i915: fix use-after-free in page_flip_completed()
    - Linux 4.4.49

  * NFS client : kernel 4.4.0-57 crash with nfsv4 enries in /etc/fstab
    (LP: #1650336)
    - SUNRPC: fix refcounting problems with auth_gss messages.

  * [0bda:0328] Card reader failed after S3 (LP: #1664809)
    - usb: hub: Wait for connection to be reestablished after port reset

  * linux-lts-xenial 4.4.0-63.84~14.04.2 ADT test failure with linux-lts-xenial
    4.4.0-63.84~14.04.2 (LP: #1664912)
    - SAUCE: apparmor: fix link auditing failure due to, uninitialized var

  * ibmvscsis: Add SGL LIMIT (LP: #1662551)
    - ibmvscsis: Add SGL limit

  * [Hyper-V] Bug fixes for storvsc (tagged queuing, error conditions)
    (LP: #1663687)
    - scsi: storvsc: Enable tracking of queue depth
    - scsi: storvsc: Remove the ...

Ok, so this bug seems to have been un-fixed (re-introduced) in 4.4.0-66, perhaps as part of the response to https://www.ubuntu.com/usn/usn-3220-1 Please re-fix (or un-re-introduce) it in a future kernel for Xenial.

Fixing this bug also solves a problem with 'fdisk -l' which is discussed on askubuntu at: http://askubuntu.com/questions/703576 The ram disks became an issue when fdisk was updated.

Also, I remember noticing ram[0..15] when I first switched to ubuntu (maybe 9.04), so I became curious. They seem to have been here since the beginning. You can find CONFIG_BLK_DEV_RAM=y in the /boot/config file of linux-image-2.6.8.1-3-386_2.6.8.1-16.1_i386.deb, which was the oldest one I could find on old-releases.ubuntu.com. If there is a prize for the longest-standing ubuntu bug, I guess this one wins it.

Thanks,
-Jeff

Hi, this bug has been fixed in 4.4.0-67, now in -proposed.

Please, verify the fix and mark the bug verified.

Thanks.
Cascardo.

@norden-jeff

It was re-introduced in 4.4.0-66 because that was a emergency CVE fix/release that used the previous kernel in -updates as it's base. A new kernel 4.4.0-67 now exists with the CVE fix as well as all the changes from -proposed which includes this fix. Please verify.

The current Xenial Kernel does fix this problem for me. Sorry that I didn't get a chance to verify this back in March.

Thanks!
-Jeff

Thank you for fixing this bug! It has been annoying me for years.