Re: [PATCH v8 0/9] Automatic NFSv4 state revocation on filesystem unmount

[Chuck Lever <cel@kernel.org>]

On 4/8/26 9:56 AM, Jeff Layton wrote:
> nit: subject is a little misleading. You're not doing this on unmount
> anymore, but rather when unexporting.

The Subject: matches what I used on the v1 posting. But you're correct,
the mission of this patch series has changed.


> On Wed, 2026-04-08 at 08:29 -0400, Chuck Lever wrote:
>> When an NFS server exports a filesystem and clients hold NFSv4
>> state (opens, locks, delegations), unmounting the underlying
>> filesystem fails with EBUSY. The /proc/fs/nfsd/unlock_ip and
>> /proc/fs/nfsd/unlock_fs procfs interfaces handle this, but have
>> no netlink equivalents, and unlock_fs operates at whole-superblock
>> granularity.
>>
>> This series adds three new NFSD netlink commands, each with its own
>> attribute set:
>>
>>  - NFSD_CMD_UNLOCK_IP releases NLM locks held by a client IP
>>    address. Netlink equivalent of write_unlock_ip.
>>
>>  - NFSD_CMD_UNLOCK_FILESYSTEM revokes all NFS state on a
>>    superblock. Netlink equivalent of write_unlock_fs.
>>
>>  - NFSD_CMD_UNLOCK_EXPORT revokes NFSv4 state acquired through
>>    exports of a specific path, regardless of client.
>>
>> UNLOCK_FILESYSTEM and UNLOCK_EXPORT serve different intents.
>> UNLOCK_FILESYSTEM means "unmounting /data, release everything
>> on this superblock." UNLOCK_EXPORT means "no clients remain for
>> /data/projectA, release only the state acquired through exports
>> of that path." Userspace (exportfs -u) sends UNLOCK_EXPORT after
>> removing the last client for a given path, enabling the underlying
>> filesystem to be unmounted.
>>
>> The path-only design for UNLOCK_EXPORT avoids the auth_domain
>> naming complexity (use_ipaddr vs hostname-based domains) by not
>> requiring the caller to identify a specific client. Since this
>> mechanism is to be used to enable umount, this seemed like a
>> reasonable compromise.
>>
>> ---
>> Changes since v7:
>> - Rebase on Jeff's mountd netlink patches
>> - Fix pre-existing state revocation bugs
>>
>> Changes since v6:
>> - Send the complete series (v5 was missing patches 6 and 7)
>>
>> Changes since v5:
>> - Rename state_lock => nn->deleg_lock
>>
>> Changes since v4:
>> - 1/9 has been queued in nfsd-testing
>> - Split single NFSD_CMD_UNLOCK into three separate commands
>> - UNLOCK_EXPORT takes path only, no client attribute to avoid
>>   auth_domain naming complexity with use_ipaddr
>>
>> Changes since v3:
>> - All VFS changes replaced with new netlink "unlock" operation
>>
>> Changes since v2:
>> - Replace fs_pin with an SRCU umount notifier chain in VFS
>> - Merge the pending COPY cancellation patch
>> - Replace xa_cmpxchg() with xa_insert()
>> - Use cancel_work_sync() instead of flush_workqueue()
>> - Remove rcu_barrier()
>> - Correct misleading claims in kdoc comments and commit messages
>>
>> Changes since v1:
>> - Explain why drop_client() is being renamed
>> - Finish implementing revocation on umount
>> - Rename pin_insert_group
>> - Clarified log output and code comments
>> - Hold nfsd_mutex while closing nfsd_files
>>
>> ---
>> Chuck Lever (9):
>>       NFSD: Fix infinite loop in layout state revocation
>>       NFSD: Handle layout stid in nfsd4_drop_revoked_stid()
>>       NFSD: Extract revoke_one_stid() utility function
>>       NFSD: Add NFSD_CMD_UNLOCK_IP netlink command
>>       NFSD: Add NFSD_CMD_UNLOCK_FILESYSTEM netlink command
>>       NFSD: Replace idr_for_each_entry_ul in find_one_sb_stid()
>>       NFSD: Track svc_export in nfs4_stid
>>       NFSD: Add NFSD_CMD_UNLOCK_EXPORT netlink command
>>       NFSD: Close cached file handles when revoking export state
>>
>>  Documentation/netlink/specs/nfsd.yaml |  61 +++++++++
>>  fs/nfsd/filecache.c                   |  46 +++++++
>>  fs/nfsd/filecache.h                   |   1 +
>>  fs/nfsd/netlink.c                     |  36 +++++
>>  fs/nfsd/netlink.h                     |   3 +
>>  fs/nfsd/nfs4layouts.c                 |   2 +
>>  fs/nfsd/nfs4state.c                   | 240 ++++++++++++++++++++++++----------
>>  fs/nfsd/nfsctl.c                      | 126 +++++++++++++++++-
>>  fs/nfsd/state.h                       |   6 +
>>  fs/nfsd/trace.h                       |  32 ++++-
>>  include/uapi/linux/nfsd_netlink.h     |  24 ++++
>>  11 files changed, 498 insertions(+), 79 deletions(-)
>> ---
>> base-commit: b495a392b2748dca31d2a4b404632c6f907aa136
>> change-id: 20260318-umount-kills-nfsv4-state-138218f2f4e0
>>
>> Best regards,
>> --  
>> Chuck Lever
> 


-- 
Chuck Lever