[GIT,PULL,net-next,v4] afs, rxrpc: Clean up refcounting on afs_cell and afs_server records

Pull-request

git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags/afs-next-20250310

Message

David Howells March 10, 2025, 1:11 p.m. UTC

Hi,

Could you pull this into the net-next tree please (it has been pulled into
the vfs tree[1])?  Besides fixing an rmmod bug, the changes made to the AFS
filesystem make it easier to use the AF_RXRPC RxGK (GSSAPI) security
class[2].

More specifically, these changes make it easier to map from the rxrpc_peer
record back to the afs_server record, thereby making it easier for AF_RXRPC
to reach out to the AFS filesystem to obtain a token to include in the
RESPONSE packet sent in reply to the AFS fileserver's security challenge.
The fileserver can then use this token to set up a secure connection back
to the client for the purpose of encrypted notifications.

These changes fix an occasional hang that's only really encountered when
rmmod'ing the kafs module, one of the reasons why I'm proposing it for the
next merge window rather than immediate upstreaming.  The changes include:

 (1) Remove the "-o autocell" mount option.  This is obsolete with the
     dynamic root and removing it makes the next patch slightly easier.

 (2) Change how the dynamic root mount is constructed.  Currently, the root
     directory is (de)populated when it is (un)mounted if there are cells
     already configured and, further, pairs of automount points have to be
     created/removed each time a cell is added/deleted.

     This is changed so that readdir on the root dir lists all the known
     cell automount pairs plus the @cell symlinks and the inodes and
     dentries are constructed by lookup on demand.  This simplifies the
     cell management code.

 (3) A few improvements to the afs_volume tracepoint.

 (4) A few improvements to the afs_server tracepoint.

 (5) Pass trace info into the afs_lookup_cell() function to allow the trace
     log to indicate the purpose of the lookup.

 (6) Remove the 'net' parameter from afs_unuse_cell() as it's superfluous.

 (7) In rxrpc, allow a kernel app (such as kafs) to store a word of
     information on rxrpc_peer records.

 (8) Use the information stored on the rxrpc_peer record to point to the
     afs_server record.  This allows the server address lookup to be done
     away with.

 (9) Simplify the afs_server ref/activity accounting to make each one
     self-contained and not garbage collected from the cell management work
     item.

(10) Simplify the afs_cell ref/activity accounting to make each one of
     these also self-contained and not driven by a central management work
     item.

     The current code was intended to make it such that a single timer for
     the namespace and one work item per cell could do all the work
     required to maintain these records.  This, however, made for some
     sequencing problems when cleaning up these records.  Further, the
     attempt to pass refs along with timers and work items made getting it
     right rather tricky when the timer or work item already had a ref
     attached and now a ref had to be got rid of.

Thanks,
David

Link: https://lore.kernel.org/r/[e-mail]/ [1]
Link: https://web.git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=rxrpc-next [2]

---
The following changes since commit 1e15510b71c99c6e49134d756df91069f7d18141:

  Merge tag 'net-6.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net (2025-02-27 09:32:42 -0800)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags/afs-next-20250310

for you to fetch changes up to e2c2cb8ef07affd9f69497ea128fa801240fdf32:

  afs: Simplify cell record handling (2025-03-10 09:47:15 +0000)

----------------------------------------------------------------
afs: Fix ref leak in rmmod

----------------------------------------------------------------
David Howells (11):
      afs: Fix afs_atcell_get_link() to handle RCU pathwalk
      afs: Remove the "autocell" mount option
      afs: Change dynroot to create contents on demand
      afs: Improve afs_volume tracing to display a debug ID
      afs: Improve server refcount/active count tracing
      afs: Make afs_lookup_cell() take a trace note
      afs: Drop the net parameter from afs_unuse_cell()
      rxrpc: Allow the app to store private data on peer structs
      afs: Use the per-peer app data provided by rxrpc
      afs: Fix afs_server ref accounting
      afs: Simplify cell record handling

 fs/afs/addr_list.c         |  50 ++++
 fs/afs/cell.c              | 446 ++++++++++++++-------------------
 fs/afs/cmservice.c         |  82 +------
 fs/afs/dir.c               |   5 +-
 fs/afs/dynroot.c           | 501 ++++++++++++++++---------------------
 fs/afs/fs_probe.c          |  32 ++-
 fs/afs/fsclient.c          |   4 +-
 fs/afs/internal.h          | 100 ++++----
 fs/afs/main.c              |  16 +-
 fs/afs/mntpt.c             |   5 +-
 fs/afs/proc.c              |  19 +-
 fs/afs/rxrpc.c             |   8 +-
 fs/afs/server.c            | 601 +++++++++++++++++++--------------------------
 fs/afs/server_list.c       |   6 +-
 fs/afs/super.c             |  25 +-
 fs/afs/vl_alias.c          |   7 +-
 fs/afs/vl_rotate.c         |   2 +-
 fs/afs/volume.c            |  15 +-
 include/net/af_rxrpc.h     |   2 +
 include/trace/events/afs.h |  83 ++++---
 net/rxrpc/ar-internal.h    |   1 +
 net/rxrpc/peer_object.c    |  30 ++-
 22 files changed, 927 insertions(+), 1113 deletions(-)