Merge tag 'vfs-6.8.cachefiles' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs cachefiles updates from Christian Brauner:
 "This contains improvements for on-demand cachefiles.

  If the daemon crashes and the on-demand cachefiles fd is unexpectedly
  closed in-flight requests and subsequent read operations associated
  with the fd will fail with EIO. This causes issues in various
  scenarios as this failure is currently unrecoverable.

  The work contained in this pull request introduces a failover mode and
  enables the daemon to recover in-flight requested-related objects. A
  restarted daemon will be able to process requests as usual.

  This requires that in-flight requests are stored during daemon crash
  or while the daemon is offline. In addition, a handle to
  /dev/cachefiles needs to be stored.

  This can be done by e.g., systemd's fdstore (cf. [1]) which enables
  the restarted daemon to recover state.

  Three new states are introduced in this patchset:

   (1) CLOSE
       Object is closed by the daemon.

   (2) OPEN
       Object is open and ready for processing. IOW, the open request
       has been handled successfully.

   (3) REOPENING
       Object has been previously closed and is now reopened due to a
       read request.

  A restarted daemon can recover the /dev/cachefiles fd from systemd's
  fdstore and writes "restore" to the device. This causes the object
  state to be reset from CLOSE to REOPENING and reinitializes the
  object.

  The daemon may now handle the open request. Any in-flight operations
  are restored and handled avoiding interruptions for users"

Link: https://systemd.io/FILE_DESCRIPTOR_STORE [1]

* tag 'vfs-6.8.cachefiles' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  cachefiles: add restore command to recover inflight ondemand read requests
  cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode
  cachefiles: resend an open request if the read request's object is closed
  cachefiles: extract ondemand info field from cachefiles_object
  cachefiles: introduce object ondemand state

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