Merge tag 'afs-fixes-b-20190516' of git://git.kernel.org/pub/scm/linux/kernel/git...

Pull AFS callback promise fixes from David Howells:
 "This series fixes a bunch of problems in callback promise handling,
  where a callback promise indicates a promise on the part of the server
  to notify the client in the event of some sort of change to a file or
  volume. In the event of a break, the client has to go and refetch the
  client status from the server and discard any cached permission
  information as the ACL might have changed.

  The problem in the current code is that changes made by other clients
  aren't always noticed, primarily because the file status information
  and the callback information aren't updated in the same critical
  section, even if these are carried in the same reply from an RPC
  operation, and so the AFS_VNODE_CB_PROMISED flag is unreliable.

  Arranging for them to be done in the same critical section during
  reply decoding is tricky because of the FS.InlineBulkStatus op - which
  has all the statuses in the reply arriving and then all the callbacks,
  so they have to be buffered. It simplifies things a lot to move the
  critical section out of the decode phase and do it after the RPC
  function returns.

  Also new inodes (either newly fetched or newly created) aren't
  properly managed against a callback break happening before we get the
  local inode up and running.

  Fix this by:

   - There's now a combined file status and callback record (struct
     afs_status_cb) to carry both plus some flags.

   - Each operation wrapper function allocates sufficient afs_status_cb
     records for all the vnodes it is interested in and passes them into
     RPC operations to be filled in from the reply.

   - The FileStatus and CallBack record decoders no longer apply the
     new/revised status and callback information to the inode/vnode at
     the point of decoding and instead store the information into the
     record from (2).

   - afs_vnode_commit_status() then revises the file status, detects
     deletion and notes callback information inside of a single critical
     section. It also checks the callback break counters and cancels the
     callback promise if they changed during the operation.

     [*] Note that "callback break counters" are counters of server
     events that cancel one or more callback promises that the client
     thinks it has. The client counts the events and compares the
     counters before and after an operation to see if the callback
     promise it thinks it just got evaporated before it got recorded
     under lock.

   - Volume and server callback break counters are passed into
     afs_iget() allowing callback breaks concurrent with inode set up to
     be detected and the callback promise thence to be cancelled.

   - AFS validation checks are now done under RCU conditions using a
     read lock on cb_lock. This requires vnode->cb_interest to be made
     RCU safe.

   - If the checks in (6) fail, the callback breaker is then called
     under write lock on the cb_lock - but only if the callback break
     counter didn't change from the value read before the checks were
     made.

   - Results from FS.InlineBulkStatus that correspond to inodes we
     currently have in memory are now used to update those inodes'
     status and callback information rather than being discarded. This
     requires those inodes to be looked up before the RPC op is made and
     all their callback break values saved.

  To aid in this, the following changes have also been made:

   - Don't pass the vnode into the reply delivery functions or the
     decoders. The vnode shouldn't be altered anywhere in those paths.
     The only exception, for the moment, is for the call done hook for
     file lock ops that wants access to both the vnode and the call -
     this can be fixed at a later time.

   - Get rid of the call->reply[] void* array and replace it with named
     and typed members. This avoids confusion since different ops were
     mapping different reply[] members to different things.

   - Fix an order-1 kmalloc allocation in afs_do_lookup() and replace it
     with kvcalloc().

   - Always get the reply time. Since callback, lock and fileserver
     record expiry times are calculated for several RPCs, make this
     mandatory.

   - Call afs_pages_written_back() from the operation wrapper rather
     than from the delivery function.

   - Don't store the version and type from a callback promise in a reply
     as the information in them is of very limited use"

* tag 'afs-fixes-b-20190516' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  afs: Fix application of the results of a inline bulk status fetch
  afs: Pass pre-fetch server and volume break counts into afs_iget5_set()
  afs: Fix unlink to handle YFS.RemoveFile2 better
  afs: Clear AFS_VNODE_CB_PROMISED if we detect callback expiry
  afs: Make vnode->cb_interest RCU safe
  afs: Split afs_validate() so first part can be used under LOOKUP_RCU
  afs: Don't save callback version and type fields
  afs: Fix application of status and callback to be under same lock
  afs: Always get the reply time
  afs: Fix order-1 allocation in afs_do_lookup()
  afs: Get rid of afs_call::reply[]
  afs: Don't pass the vnode pointer through into the inline bulk status op