Allow multiple mounts of zfs datasets

Applied patch, tested successfully with:

mount -t zfs -o zfsutil pool/ds /mnt/first
mount -t zfs -o zfsutil pool/ds /mnt/second

And also passes the ubuntu ZFS regression tests.

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1759848

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.

This bug was fixed in the package zfs-linux - 0.7.5-1ubuntu13

---------------
zfs-linux (0.7.5-1ubuntu13) bionic; urgency=medium

  * Allow multiple mounts of zfs datasets (LP: #1759848)
    - Change zpl_mount() to call sget() directly with it's own test
      callback. Passing the objset_t object as the fs data allows
      checking if a superblock already exists for the dataset, and in
      that case we just need to return a new reference for the sb's
      root dentry.

 -- Colin Ian King <email address hidden> Thu, 29 Mar 2018 13:58:22 +0100

This bug was fixed in the package linux - 4.15.0-15.16

---------------
linux (4.15.0-15.16) bionic; urgency=medium

  * linux: 4.15.0-15.16 -proposed tracker (LP: #1761177)

  * FFe: Enable configuring resume offset via sysfs (LP: #1760106)
    - PM / hibernate: Make passing hibernate offsets more friendly

  * /dev/bcache/by-uuid links not created after reboot (LP: #1729145)
    - SAUCE: (no-up) bcache: decouple emitting a cached_dev CHANGE uevent

  * Ubuntu18.04:POWER9:DD2.2 - Unable to start a KVM guest with default machine
    type(pseries-bionic) complaining "KVM implementation does not support
    Transactional Memory, try cap-htm=off" (kvm) (LP: #1752026)
    - powerpc: Use feature bit for RTC presence rather than timebase presence
    - powerpc: Book E: Remove unused CPU_FTR_L2CSR bit
    - powerpc: Free up CPU feature bits on 64-bit machines
    - powerpc: Add CPU feature bits for TM bug workarounds on POWER9 v2.2
    - powerpc/powernv: Provide a way to force a core into SMT4 mode
    - KVM: PPC: Book3S HV: Work around transactional memory bugs in POWER9
    - KVM: PPC: Book3S HV: Work around XER[SO] bug in fake suspend mode
    - KVM: PPC: Book3S HV: Work around TEXASR bug in fake suspend state

  * Important Kernel fixes to be backported for Power9 (kvm) (LP: #1758910)
    - powerpc/mm: Fixup tlbie vs store ordering issue on POWER9

  * Ubuntu 18.04 - IO Hang on some namespaces when running HTX with 16
    namespaces (Bolt / NVMe) (LP: #1757497)
    - powerpc/64s: Fix lost pending interrupt due to race causing lost update to
      irq_happened

  * fwts-efi-runtime-dkms 18.03.00-0ubuntu1: fwts-efi-runtime-dkms kernel module
    failed to build (LP: #1760876)
    - [Packaging] include the retpoline extractor in the headers

linux (4.15.0-14.15) bionic; urgency=medium

  * linux: 4.15.0-14.15 -proposed tracker (LP: #1760678)

  * [Bionic] mlx4 ETH - mlnx_qos failed when set some TC to vendor
    (LP: #1758662)
    - net/mlx4_en: Change default QoS settings

  * AT_BASE_PLATFORM in AUXV is absent on kernels available on Ubuntu 17.10
    (LP: #1759312)
    - powerpc/64s: Fix NULL AT_BASE_PLATFORM when using DT CPU features

  * Bionic update to 4.15.15 stable release (LP: #1760585)
    - net: dsa: Fix dsa_is_user_port() test inversion
    - openvswitch: meter: fix the incorrect calculation of max delta_t
    - qed: Fix MPA unalign flow in case header is split across two packets.
    - tcp: purge write queue upon aborting the connection
    - qed: Fix non TCP packets should be dropped on iWARP ll2 connection
    - sysfs: symlink: export sysfs_create_link_nowarn()
    - net: phy: relax error checking when creating sysfs link netdev->phydev
    - devlink: Remove redundant free on error path
    - macvlan: filter out unsupported feature flags
    - net: ipv6: keep sk status consistent after datagram connect failure
    - ipv6: old_dport should be a __be16 in __ip6_datagram_connect()
    - ipv6: sr: fix NULL pointer dereference when setting encap source address
    - ipv6: sr: fix scheduling in RCU when creating seg6 lwtunnel state
    - mlxsw: spectrum_buffers: Set a minimum quota for CPU port traffic
    - net: phy: Tell caller result ...

This SRU requires and update in zfsutils-linux and the change sync'd to the kernel and the kernel update to complete the fix.

Hello Colin, or anyone else affected,

Accepted zfs-linux into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/zfs-linux/0.6.5.6-0ubuntu24 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-xenial to verification-done-xenial. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-xenial. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

We need to wait until the kernel is updated with the fix before it can be tested as the fixes require kernel + zfs together to work

Tested with kernel 4.15.0-27-generic and the fix works. Marking as verified for Bionic.

Tested with zfsutils-linux 0.6.5.6-0ubuntu24 and linux 4.4.0-134 with test in comment #2 and this now works. Marking as verified for Xenial

This bug was fixed in the package zfs-linux - 0.6.5.6-0ubuntu24

---------------
zfs-linux (0.6.5.6-0ubuntu24) xenial; urgency=medium

  * Allow multiple mounts of zfs datasets (LP: #1759848)
    - Change zpl_mount() to call sget() directly with it's own test
      callback. Passing the objset_t object as the fs data allows
      checking if a superblock already exists for the dataset, and in
      that case we just need to return a new reference for the sb's
      root dentry.

 -- Colin Ian King <email address hidden> Thu, 25 Jun 2018 14:31:14 +0100

The verification of the Stable Release Update for zfs-linux has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

This bug was fixed in the package linux - 4.4.0-134.160

---------------
linux (4.4.0-134.160) xenial; urgency=medium

  * linux: 4.4.0-134.160 -proposed tracker (LP: #1787177)

  * locking sockets broken due to missing AppArmor socket mediation patches
    (LP: #1780227)
    - UBUNTU SAUCE: apparmor: fix apparmor mediating locking non-fs, unix sockets

  * Backport namespaced fscaps to xenial 4.4 (LP: #1778286)
    - Introduce v3 namespaced file capabilities
    - commoncap: move assignment of fs_ns to avoid null pointer dereference
    - capabilities: fix buffer overread on very short xattr
    - commoncap: Handle memory allocation failure.

  * Xenial update to 4.4.140 stable release (LP: #1784409)
    - usb: cdc_acm: Add quirk for Uniden UBC125 scanner
    - USB: serial: cp210x: add CESINEL device ids
    - USB: serial: cp210x: add Silicon Labs IDs for Windows Update
    - n_tty: Fix stall at n_tty_receive_char_special().
    - staging: android: ion: Return an ERR_PTR in ion_map_kernel
    - n_tty: Access echo_* variables carefully.
    - x86/boot: Fix early command-line parsing when matching at end
    - ath10k: fix rfc1042 header retrieval in QCA4019 with eth decap mode
    - i2c: rcar: fix resume by always initializing registers before transfer
    - ipv4: Fix error return value in fib_convert_metrics()
    - kprobes/x86: Do not modify singlestep buffer while resuming
    - nvme-pci: initialize queue memory before interrupts
    - netfilter: nf_tables: use WARN_ON_ONCE instead of BUG_ON in nft_do_chain()
    - ARM: dts: imx6q: Use correct SDMA script for SPI5 core
    - ubi: fastmap: Correctly handle interrupted erasures in EBA
    - mm: hugetlb: yield when prepping struct pages
    - tracing: Fix missing return symbol in function_graph output
    - scsi: sg: mitigate read/write abuse
    - s390: Correct register corruption in critical section cleanup
    - drbd: fix access after free
    - cifs: Fix infinite loop when using hard mount option
    - jbd2: don't mark block as modified if the handle is out of credits
    - ext4: make sure bitmaps and the inode table don't overlap with bg
      descriptors
    - ext4: always check block group bounds in ext4_init_block_bitmap()
    - ext4: only look at the bg_flags field if it is valid
    - ext4: verify the depth of extent tree in ext4_find_extent()
    - ext4: include the illegal physical block in the bad map ext4_error msg
    - ext4: clear i_data in ext4_inode_info when removing inline data
    - ext4: add more inode number paranoia checks
    - ext4: add more mount time checks of the superblock
    - ext4: check superblock mapped prior to committing
    - HID: i2c-hid: Fix "incomplete report" noise
    - HID: hiddev: fix potential Spectre v1
    - HID: debug: check length before copy_to_user()
    - x86/mce: Detect local MCEs properly
    - x86/mce: Fix incorrect "Machine check from unknown source" message
    - media: cx25840: Use subdev host data for PLL override
    - mm, page_alloc: do not break __GFP_THISNODE by zonelist reset
    - dm bufio: avoid sleeping while holding the dm_bufio lock
    - dm bufio: drop the lock when doing GFP_NOIO allocation
    - mtd: rawnand: mxc: set spa...

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-bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed-bionic'.

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 was erroneously marked for verification in bionic; verification is not required and verification-needed-bionic is being removed.