FS-Cache: Fix object state machine to have separate work and wait states
[firefly-linux-kernel-4.4.55.git] / fs / fscache / object.c
index 863f6873c0f035cb723e59c2a75fd929ed66c53a..8f17debd7979fbe13e41acd69bc64b06834b0987 100644 (file)
 #define FSCACHE_DEBUG_LEVEL COOKIE
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/prefetch.h>
 #include "internal.h"
 
-const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
-       [FSCACHE_OBJECT_INIT]           = "OBJECT_INIT",
-       [FSCACHE_OBJECT_LOOKING_UP]     = "OBJECT_LOOKING_UP",
-       [FSCACHE_OBJECT_CREATING]       = "OBJECT_CREATING",
-       [FSCACHE_OBJECT_AVAILABLE]      = "OBJECT_AVAILABLE",
-       [FSCACHE_OBJECT_ACTIVE]         = "OBJECT_ACTIVE",
-       [FSCACHE_OBJECT_INVALIDATING]   = "OBJECT_INVALIDATING",
-       [FSCACHE_OBJECT_UPDATING]       = "OBJECT_UPDATING",
-       [FSCACHE_OBJECT_DYING]          = "OBJECT_DYING",
-       [FSCACHE_OBJECT_LC_DYING]       = "OBJECT_LC_DYING",
-       [FSCACHE_OBJECT_ABORT_INIT]     = "OBJECT_ABORT_INIT",
-       [FSCACHE_OBJECT_RELEASING]      = "OBJECT_RELEASING",
-       [FSCACHE_OBJECT_RECYCLING]      = "OBJECT_RECYCLING",
-       [FSCACHE_OBJECT_WITHDRAWING]    = "OBJECT_WITHDRAWING",
-       [FSCACHE_OBJECT_DEAD]           = "OBJECT_DEAD",
+static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *, int);
+static const struct fscache_state *fscache_kill_dependents(struct fscache_object *, int);
+static const struct fscache_state *fscache_drop_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_initialise_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_invalidate_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *, int);
+static const struct fscache_state *fscache_kill_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_lookup_failure(struct fscache_object *, int);
+static const struct fscache_state *fscache_look_up_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_object_available(struct fscache_object *, int);
+static const struct fscache_state *fscache_parent_ready(struct fscache_object *, int);
+static const struct fscache_state *fscache_update_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_detach_from_cookie(struct fscache_object *, int);
+
+#define __STATE_NAME(n) fscache_osm_##n
+#define STATE(n) (&__STATE_NAME(n))
+
+/*
+ * Define a work state.  Work states are execution states.  No event processing
+ * is performed by them.  The function attached to a work state returns a
+ * pointer indicating the next state to which the state machine should
+ * transition.  Returning NO_TRANSIT repeats the current state, but goes back
+ * to the scheduler first.
+ */
+#define WORK_STATE(n, sn, f) \
+       const struct fscache_state __STATE_NAME(n) = {                  \
+               .name = #n,                                             \
+               .short_name = sn,                                       \
+               .work = f                                               \
+       }
+
+/*
+ * Returns from work states.
+ */
+#define transit_to(state) ({ prefetch(&STATE(state)->work); STATE(state); })
+
+#define NO_TRANSIT ((struct fscache_state *)NULL)
+
+/*
+ * Define a wait state.  Wait states are event processing states.  No execution
+ * is performed by them.  Wait states are just tables of "if event X occurs,
+ * clear it and transition to state Y".  The dispatcher returns to the
+ * scheduler if none of the events in which the wait state has an interest are
+ * currently pending.
+ */
+#define WAIT_STATE(n, sn, ...) \
+       const struct fscache_state __STATE_NAME(n) = {                  \
+               .name = #n,                                             \
+               .short_name = sn,                                       \
+               .work = NULL,                                           \
+               .transitions = { __VA_ARGS__, { 0, NULL } }             \
+       }
+
+#define TRANSIT_TO(state, emask) \
+       { .events = (emask), .transit_to = STATE(state) }
+
+/*
+ * The object state machine.
+ */
+static WORK_STATE(INIT_OBJECT,         "INIT", fscache_initialise_object);
+static WORK_STATE(PARENT_READY,                "PRDY", fscache_parent_ready);
+static WORK_STATE(ABORT_INIT,          "ABRT", fscache_abort_initialisation);
+static WORK_STATE(LOOK_UP_OBJECT,      "LOOK", fscache_look_up_object);
+static WORK_STATE(CREATE_OBJECT,       "CRTO", fscache_look_up_object);
+static WORK_STATE(OBJECT_AVAILABLE,    "AVBL", fscache_object_available);
+static WORK_STATE(JUMPSTART_DEPS,      "JUMP", fscache_jumpstart_dependents);
+
+static WORK_STATE(INVALIDATE_OBJECT,   "INVL", fscache_invalidate_object);
+static WORK_STATE(UPDATE_OBJECT,       "UPDT", fscache_update_object);
+
+static WORK_STATE(LOOKUP_FAILURE,      "LCFL", fscache_lookup_failure);
+static WORK_STATE(KILL_OBJECT,         "KILL", fscache_kill_object);
+static WORK_STATE(KILL_DEPENDENTS,     "KDEP", fscache_kill_dependents);
+static WORK_STATE(DROP_OBJECT,         "DROP", fscache_drop_object);
+static WORK_STATE(DETACH_FROM_COOKIE,  "DTCH", fscache_detach_from_cookie);
+static WORK_STATE(OBJECT_DEAD,         "DEAD", (void*)2UL);
+
+static WAIT_STATE(WAIT_FOR_INIT,       "?INI",
+                 TRANSIT_TO(INIT_OBJECT,       1 << FSCACHE_OBJECT_EV_NEW_CHILD));
+
+static WAIT_STATE(WAIT_FOR_PARENT,     "?PRN",
+                 TRANSIT_TO(PARENT_READY,      1 << FSCACHE_OBJECT_EV_PARENT_READY));
+
+static WAIT_STATE(WAIT_FOR_CMD,                "?CMD",
+                 TRANSIT_TO(INVALIDATE_OBJECT, 1 << FSCACHE_OBJECT_EV_INVALIDATE),
+                 TRANSIT_TO(UPDATE_OBJECT,     1 << FSCACHE_OBJECT_EV_UPDATE),
+                 TRANSIT_TO(JUMPSTART_DEPS,    1 << FSCACHE_OBJECT_EV_NEW_CHILD));
+
+static WAIT_STATE(WAIT_FOR_CLEARANCE,  "?CLR",
+                 TRANSIT_TO(KILL_OBJECT,       1 << FSCACHE_OBJECT_EV_CLEARED));
+
+/*
+ * Out-of-band event transition tables.  These are for handling unexpected
+ * events, such as an I/O error.  If an OOB event occurs, the state machine
+ * clears and disables the event and forces a transition to the nominated work
+ * state (acurrently executing work states will complete first).
+ *
+ * In such a situation, object->state remembers the state the machine should
+ * have been in/gone to and returning NO_TRANSIT returns to that.
+ */
+static const struct fscache_transition fscache_osm_init_oob[] = {
+          TRANSIT_TO(ABORT_INIT,
+                     (1 << FSCACHE_OBJECT_EV_ERROR) |
+                     (1 << FSCACHE_OBJECT_EV_KILL)),
+          { 0, NULL }
 };
-EXPORT_SYMBOL(fscache_object_states);
-
-const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
-       [FSCACHE_OBJECT_INIT]           = "INIT",
-       [FSCACHE_OBJECT_LOOKING_UP]     = "LOOK",
-       [FSCACHE_OBJECT_CREATING]       = "CRTN",
-       [FSCACHE_OBJECT_AVAILABLE]      = "AVBL",
-       [FSCACHE_OBJECT_ACTIVE]         = "ACTV",
-       [FSCACHE_OBJECT_INVALIDATING]   = "INVL",
-       [FSCACHE_OBJECT_UPDATING]       = "UPDT",
-       [FSCACHE_OBJECT_DYING]          = "DYNG",
-       [FSCACHE_OBJECT_LC_DYING]       = "LCDY",
-       [FSCACHE_OBJECT_ABORT_INIT]     = "ABTI",
-       [FSCACHE_OBJECT_RELEASING]      = "RELS",
-       [FSCACHE_OBJECT_RECYCLING]      = "RCYC",
-       [FSCACHE_OBJECT_WITHDRAWING]    = "WTHD",
-       [FSCACHE_OBJECT_DEAD]           = "DEAD",
+
+static const struct fscache_transition fscache_osm_lookup_oob[] = {
+          TRANSIT_TO(LOOKUP_FAILURE,
+                     (1 << FSCACHE_OBJECT_EV_ERROR) |
+                     (1 << FSCACHE_OBJECT_EV_KILL)),
+          { 0, NULL }
+};
+
+static const struct fscache_transition fscache_osm_run_oob[] = {
+          TRANSIT_TO(KILL_OBJECT,
+                     (1 << FSCACHE_OBJECT_EV_ERROR) |
+                     (1 << FSCACHE_OBJECT_EV_KILL)),
+          { 0, NULL }
 };
 
 static int  fscache_get_object(struct fscache_object *);
 static void fscache_put_object(struct fscache_object *);
-static void fscache_initialise_object(struct fscache_object *);
-static void fscache_lookup_object(struct fscache_object *);
-static void fscache_object_available(struct fscache_object *);
-static void fscache_invalidate_object(struct fscache_object *);
-static void fscache_release_object(struct fscache_object *);
-static void fscache_withdraw_object(struct fscache_object *);
-static void fscache_enqueue_dependents(struct fscache_object *);
+static bool fscache_enqueue_dependents(struct fscache_object *, int);
 static void fscache_dequeue_object(struct fscache_object *);
 
 /*
@@ -83,281 +164,102 @@ static inline void fscache_done_parent_op(struct fscache_object *object)
 }
 
 /*
- * Notify netfs of invalidation completion.
+ * Object state machine dispatcher.
  */
-static inline void fscache_invalidation_complete(struct fscache_cookie *cookie)
+static void fscache_object_sm_dispatcher(struct fscache_object *object)
 {
-       if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
-               wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
-}
-
-/*
- * process events that have been sent to an object's state machine
- * - initiates parent lookup
- * - does object lookup
- * - does object creation
- * - does object recycling and retirement
- * - does object withdrawal
- */
-static void fscache_object_state_machine(struct fscache_object *object)
-{
-       enum fscache_object_state new_state;
-       struct fscache_cookie *cookie;
-       int event;
+       const struct fscache_transition *t;
+       const struct fscache_state *state, *new_state;
+       unsigned long events, event_mask;
+       int event = -1;
 
        ASSERT(object != NULL);
 
        _enter("{OBJ%x,%s,%lx}",
-              object->debug_id, fscache_object_states[object->state],
-              object->events);
-
-       switch (object->state) {
-               /* wait for the parent object to become ready */
-       case FSCACHE_OBJECT_INIT:
-               object->event_mask =
-                       FSCACHE_OBJECT_EVENTS_MASK &
-                       ~(1 << FSCACHE_OBJECT_EV_CLEARED);
-               fscache_initialise_object(object);
-               goto done;
-
-               /* look up the object metadata on disk */
-       case FSCACHE_OBJECT_LOOKING_UP:
-               fscache_lookup_object(object);
-               goto lookup_transit;
-
-               /* create the object metadata on disk */
-       case FSCACHE_OBJECT_CREATING:
-               fscache_lookup_object(object);
-               goto lookup_transit;
-
-               /* handle an object becoming available; start pending
-                * operations and queue dependent operations for processing */
-       case FSCACHE_OBJECT_AVAILABLE:
-               fscache_object_available(object);
-               goto active_transit;
-
-               /* normal running state */
-       case FSCACHE_OBJECT_ACTIVE:
-               goto active_transit;
-
-               /* Invalidate an object on disk */
-       case FSCACHE_OBJECT_INVALIDATING:
-               clear_bit(FSCACHE_OBJECT_EV_INVALIDATE, &object->events);
-               fscache_stat(&fscache_n_invalidates_run);
-               fscache_stat(&fscache_n_cop_invalidate_object);
-               fscache_invalidate_object(object);
-               fscache_stat_d(&fscache_n_cop_invalidate_object);
-               fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
-               goto active_transit;
-
-               /* update the object metadata on disk */
-       case FSCACHE_OBJECT_UPDATING:
-               clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
-               fscache_stat(&fscache_n_updates_run);
-               fscache_stat(&fscache_n_cop_update_object);
-               object->cache->ops->update_object(object);
-               fscache_stat_d(&fscache_n_cop_update_object);
-               goto active_transit;
-
-               /* handle an object dying during lookup or creation */
-       case FSCACHE_OBJECT_LC_DYING:
-               object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
-               fscache_stat(&fscache_n_cop_lookup_complete);
-               object->cache->ops->lookup_complete(object);
-               fscache_stat_d(&fscache_n_cop_lookup_complete);
-
-               spin_lock(&object->lock);
-               object->state = FSCACHE_OBJECT_DYING;
-               cookie = object->cookie;
-               if (cookie) {
-                       if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
-                                              &cookie->flags))
-                               wake_up_bit(&cookie->flags,
-                                           FSCACHE_COOKIE_LOOKING_UP);
-                       if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
-                                              &cookie->flags))
-                               wake_up_bit(&cookie->flags,
-                                           FSCACHE_COOKIE_CREATING);
+              object->debug_id, object->state->name, object->events);
+
+       event_mask = object->event_mask;
+restart:
+       object->event_mask = 0; /* Mask normal event handling */
+       state = object->state;
+restart_masked:
+       events = object->events;
+
+       /* Handle any out-of-band events (typically an error) */
+       if (events & object->oob_event_mask) {
+               _debug("{OBJ%x} oob %lx",
+                      object->debug_id, events & object->oob_event_mask);
+               for (t = object->oob_table; t->events; t++) {
+                       if (events & t->events) {
+                               state = t->transit_to;
+                               ASSERT(state->work != NULL);
+                               event = fls(events & t->events) - 1;
+                               __clear_bit(event, &object->oob_event_mask);
+                               clear_bit(event, &object->events);
+                               goto execute_work_state;
+                       }
                }
-               spin_unlock(&object->lock);
+       }
 
-               fscache_done_parent_op(object);
+       /* Wait states are just transition tables */
+       if (!state->work) {
+               if (events & event_mask) {
+                       for (t = state->transitions; t->events; t++) {
+                               if (events & t->events) {
+                                       new_state = t->transit_to;
+                                       event = fls(events & t->events) - 1;
+                                       clear_bit(event, &object->events);
+                                       _debug("{OBJ%x} ev %d: %s -> %s",
+                                              object->debug_id, event,
+                                              state->name, new_state->name);
+                                       object->state = state = new_state;
+                                       goto execute_work_state;
+                               }
+                       }
 
-               /* wait for completion of all active operations on this object
-                * and the death of all child objects of this object */
-       case FSCACHE_OBJECT_DYING:
-       dying:
-               clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
-               spin_lock(&object->lock);
-               _debug("dying OBJ%x {%d,%d}",
-                      object->debug_id, object->n_ops, object->n_children);
-               if (object->n_ops == 0 && object->n_children == 0) {
-                       object->event_mask &=
-                               ~(1 << FSCACHE_OBJECT_EV_CLEARED);
-                       object->event_mask |=
-                               (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
-                               (1 << FSCACHE_OBJECT_EV_RETIRE) |
-                               (1 << FSCACHE_OBJECT_EV_RELEASE) |
-                               (1 << FSCACHE_OBJECT_EV_ERROR);
-               } else {
-                       object->event_mask &=
-                               ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
-                                 (1 << FSCACHE_OBJECT_EV_RETIRE) |
-                                 (1 << FSCACHE_OBJECT_EV_RELEASE) |
-                                 (1 << FSCACHE_OBJECT_EV_ERROR));
-                       object->event_mask |=
-                               1 << FSCACHE_OBJECT_EV_CLEARED;
+                       /* The event mask didn't include all the tabled bits */
+                       BUG();
                }
-               spin_unlock(&object->lock);
-               fscache_enqueue_dependents(object);
-               fscache_start_operations(object);
-               goto terminal_transit;
-
-               /* handle an abort during initialisation */
-       case FSCACHE_OBJECT_ABORT_INIT:
-               _debug("handle abort init %lx", object->events);
-               object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
-
-               spin_lock(&object->lock);
-               fscache_dequeue_object(object);
-
-               object->state = FSCACHE_OBJECT_DYING;
-               if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
-                                      &object->cookie->flags))
-                       wake_up_bit(&object->cookie->flags,
-                                   FSCACHE_COOKIE_CREATING);
-               spin_unlock(&object->lock);
-               goto dying;
-
-               /* handle the netfs releasing an object and possibly marking it
-                * obsolete too */
-       case FSCACHE_OBJECT_RELEASING:
-       case FSCACHE_OBJECT_RECYCLING:
-               object->event_mask &=
-                       ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
-                         (1 << FSCACHE_OBJECT_EV_RETIRE) |
-                         (1 << FSCACHE_OBJECT_EV_RELEASE) |
-                         (1 << FSCACHE_OBJECT_EV_ERROR));
-               fscache_release_object(object);
-               spin_lock(&object->lock);
-               object->state = FSCACHE_OBJECT_DEAD;
-               spin_unlock(&object->lock);
-               fscache_stat(&fscache_n_object_dead);
-               goto terminal_transit;
-
-               /* handle the parent cache of this object being withdrawn from
-                * active service */
-       case FSCACHE_OBJECT_WITHDRAWING:
-               object->event_mask &=
-                       ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
-                         (1 << FSCACHE_OBJECT_EV_RETIRE) |
-                         (1 << FSCACHE_OBJECT_EV_RELEASE) |
-                         (1 << FSCACHE_OBJECT_EV_ERROR));
-               fscache_withdraw_object(object);
-               spin_lock(&object->lock);
-               object->state = FSCACHE_OBJECT_DEAD;
-               spin_unlock(&object->lock);
-               fscache_stat(&fscache_n_object_dead);
-               goto terminal_transit;
-
-               /* complain about the object being woken up once it is
-                * deceased */
-       case FSCACHE_OBJECT_DEAD:
-               printk(KERN_ERR "FS-Cache:"
-                      " Unexpected event in dead state %lx\n",
-                      object->events & object->event_mask);
-               BUG();
-
-       default:
-               printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
-                      object->state);
-               BUG();
+               /* Randomly woke up */
+               goto unmask_events;
        }
 
-       /* determine the transition from a lookup state */
-lookup_transit:
-       event = fls(object->events & object->event_mask) - 1;
-       switch (event) {
-       case FSCACHE_OBJECT_EV_WITHDRAW:
-       case FSCACHE_OBJECT_EV_RETIRE:
-       case FSCACHE_OBJECT_EV_RELEASE:
-       case FSCACHE_OBJECT_EV_ERROR:
-               new_state = FSCACHE_OBJECT_LC_DYING;
-               goto change_state;
-       case FSCACHE_OBJECT_EV_INVALIDATE:
-               new_state = FSCACHE_OBJECT_INVALIDATING;
-               goto change_state;
-       case FSCACHE_OBJECT_EV_REQUEUE:
-               goto done;
-       case -1:
-               goto done; /* sleep until event */
-       default:
-               goto unsupported_event;
-       }
-
-       /* determine the transition from an active state */
-active_transit:
-       event = fls(object->events & object->event_mask) - 1;
-       switch (event) {
-       case FSCACHE_OBJECT_EV_WITHDRAW:
-       case FSCACHE_OBJECT_EV_RETIRE:
-       case FSCACHE_OBJECT_EV_RELEASE:
-       case FSCACHE_OBJECT_EV_ERROR:
-               new_state = FSCACHE_OBJECT_DYING;
-               goto change_state;
-       case FSCACHE_OBJECT_EV_INVALIDATE:
-               new_state = FSCACHE_OBJECT_INVALIDATING;
-               goto change_state;
-       case FSCACHE_OBJECT_EV_UPDATE:
-               new_state = FSCACHE_OBJECT_UPDATING;
-               goto change_state;
-       case -1:
-               new_state = FSCACHE_OBJECT_ACTIVE;
-               goto change_state; /* sleep until event */
-       default:
-               goto unsupported_event;
-       }
+execute_work_state:
+       _debug("{OBJ%x} exec %s", object->debug_id, state->name);
 
-       /* determine the transition from a terminal state */
-terminal_transit:
-       event = fls(object->events & object->event_mask) - 1;
-       switch (event) {
-       case FSCACHE_OBJECT_EV_WITHDRAW:
-               new_state = FSCACHE_OBJECT_WITHDRAWING;
-               goto change_state;
-       case FSCACHE_OBJECT_EV_RETIRE:
-               new_state = FSCACHE_OBJECT_RECYCLING;
-               goto change_state;
-       case FSCACHE_OBJECT_EV_RELEASE:
-               new_state = FSCACHE_OBJECT_RELEASING;
-               goto change_state;
-       case FSCACHE_OBJECT_EV_ERROR:
-               new_state = FSCACHE_OBJECT_WITHDRAWING;
-               goto change_state;
-       case FSCACHE_OBJECT_EV_CLEARED:
-               new_state = FSCACHE_OBJECT_DYING;
-               goto change_state;
-       case -1:
-               goto done; /* sleep until event */
-       default:
-               goto unsupported_event;
+       new_state = state->work(object, event);
+       event = -1;
+       if (new_state == NO_TRANSIT) {
+               _debug("{OBJ%x} %s notrans", object->debug_id, state->name);
+               fscache_enqueue_object(object);
+               event_mask = object->oob_event_mask;
+               goto unmask_events;
        }
 
-change_state:
-       spin_lock(&object->lock);
-       object->state = new_state;
-       spin_unlock(&object->lock);
+       _debug("{OBJ%x} %s -> %s",
+              object->debug_id, state->name, new_state->name);
+       object->state = state = new_state;
 
-done:
-       _leave(" [->%s]", fscache_object_states[object->state]);
-       return;
+       if (state->work) {
+               if (unlikely(state->work == ((void *)2UL))) {
+                       _leave(" [dead]");
+                       return;
+               }
+               goto restart_masked;
+       }
 
-unsupported_event:
-       printk(KERN_ERR "FS-Cache:"
-              " Unsupported event %d [%lx/%lx] in state %s\n",
-              event, object->events, object->event_mask,
-              fscache_object_states[object->state]);
-       BUG();
+       /* Transited to wait state */
+       event_mask = object->oob_event_mask;
+       for (t = state->transitions; t->events; t++)
+               event_mask |= t->events;
+
+unmask_events:
+       object->event_mask = event_mask;
+       smp_mb();
+       events = object->events;
+       if (events & event_mask)
+               goto restart;
+       _leave(" [msk %lx]", event_mask);
 }
 
 /*
@@ -372,11 +274,8 @@ static void fscache_object_work_func(struct work_struct *work)
        _enter("{OBJ%x}", object->debug_id);
 
        start = jiffies;
-       fscache_object_state_machine(object);
+       fscache_object_sm_dispatcher(object);
        fscache_hist(fscache_objs_histogram, start);
-       if (object->events & object->event_mask)
-               fscache_enqueue_object(object);
-       clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
        fscache_put_object(object);
 }
 
@@ -395,9 +294,13 @@ void fscache_object_init(struct fscache_object *object,
                         struct fscache_cookie *cookie,
                         struct fscache_cache *cache)
 {
+       const struct fscache_transition *t;
+
        atomic_inc(&cache->object_count);
 
-       object->state = FSCACHE_OBJECT_INIT;
+       object->state = STATE(WAIT_FOR_INIT);
+       object->oob_table = fscache_osm_init_oob;
+       object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
        spin_lock_init(&object->lock);
        INIT_LIST_HEAD(&object->cache_link);
        INIT_HLIST_NODE(&object->cookie_link);
@@ -407,16 +310,47 @@ void fscache_object_init(struct fscache_object *object,
        INIT_LIST_HEAD(&object->pending_ops);
        object->n_children = 0;
        object->n_ops = object->n_in_progress = object->n_exclusive = 0;
-       object->events = object->event_mask = 0;
-       object->flags = 0;
+       object->events = 0;
        object->store_limit = 0;
        object->store_limit_l = 0;
        object->cache = cache;
        object->cookie = cookie;
        object->parent = NULL;
+
+       object->oob_event_mask = 0;
+       for (t = object->oob_table; t->events; t++)
+               object->oob_event_mask |= t->events;
+       object->event_mask = object->oob_event_mask;
+       for (t = object->state->transitions; t->events; t++)
+               object->event_mask |= t->events;
 }
 EXPORT_SYMBOL(fscache_object_init);
 
+/*
+ * Abort object initialisation before we start it.
+ */
+static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
+                                                               int event)
+{
+       struct fscache_cookie *cookie;
+
+       _enter("{OBJ%x},%d", object->debug_id, event);
+
+       object->oob_event_mask = 0;
+       clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
+
+       fscache_dequeue_object(object);
+
+       spin_lock(&object->lock);
+       cookie = object->cookie;
+       clear_bit_unlock(FSCACHE_COOKIE_CREATING, &cookie->flags);
+       spin_unlock(&object->lock);
+
+       wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
+
+       return transit_to(KILL_OBJECT);
+}
+
 /*
  * initialise an object
  * - check the specified object's parent to see if we can make use of it
@@ -426,74 +360,78 @@ EXPORT_SYMBOL(fscache_object_init);
  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
  *   leaf-most cookies of the object and all its children
  */
-static void fscache_initialise_object(struct fscache_object *object)
+static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
+                                                            int event)
 {
        struct fscache_object *parent;
+       bool success;
 
-       _enter("");
-       ASSERT(object->cookie != NULL);
-       ASSERT(object->cookie->parent != NULL);
+       _enter("{OBJ%x},%d", object->debug_id, event);
 
-       if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
-                             (1 << FSCACHE_OBJECT_EV_RELEASE) |
-                             (1 << FSCACHE_OBJECT_EV_RETIRE) |
-                             (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
-               _debug("abort init %lx", object->events);
-               spin_lock(&object->lock);
-               object->state = FSCACHE_OBJECT_ABORT_INIT;
-               spin_unlock(&object->lock);
-               return;
-       }
-
-       spin_lock(&object->cookie->lock);
-       spin_lock_nested(&object->cookie->parent->lock, 1);
+       ASSERT(list_empty(&object->dep_link));
 
        parent = object->parent;
        if (!parent) {
-               _debug("no parent");
-               set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
-       } else {
-               spin_lock(&object->lock);
-               spin_lock_nested(&parent->lock, 1);
-               _debug("parent %s", fscache_object_states[parent->state]);
-
-               if (fscache_object_is_dying(parent)) {
-                       _debug("bad parent");
-                       set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
-               } else if (!fscache_object_is_available(parent)) {
-                       _debug("wait");
-
-                       /* we may get woken up in this state by child objects
-                        * binding on to us, so we need to make sure we don't
-                        * add ourself to the list multiple times */
-                       if (list_empty(&object->dep_link)) {
-                               fscache_stat(&fscache_n_cop_grab_object);
-                               object->cache->ops->grab_object(object);
-                               fscache_stat_d(&fscache_n_cop_grab_object);
-                               list_add(&object->dep_link,
-                                        &parent->dependents);
-
-                               /* fscache_acquire_non_index_cookie() uses this
-                                * to wake the chain up */
-                               if (parent->state == FSCACHE_OBJECT_INIT)
-                                       fscache_enqueue_object(parent);
-                       }
-               } else {
-                       _debug("go");
-                       parent->n_ops++;
-                       parent->n_obj_ops++;
-                       object->lookup_jif = jiffies;
-                       object->state = FSCACHE_OBJECT_LOOKING_UP;
-                       set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
-               }
+               _leave(" [no parent]");
+               return transit_to(DETACH_FROM_COOKIE);
+       }
 
-               spin_unlock(&parent->lock);
-               spin_unlock(&object->lock);
+       _debug("parent %s", parent->state->name);
+
+       if (fscache_object_is_dying(parent)) {
+               _leave(" [bad parent]");
+               return transit_to(DETACH_FROM_COOKIE);
+       }
+
+       if (fscache_object_is_available(parent)) {
+               _leave(" [ready]");
+               return transit_to(PARENT_READY);
+       }
+
+       _debug("wait");
+
+       spin_lock(&parent->lock);
+       fscache_stat(&fscache_n_cop_grab_object);
+       success = false;
+       if (fscache_object_is_live(parent) &&
+           object->cache->ops->grab_object(object)) {
+               list_add(&object->dep_link, &parent->dependents);
+               success = true;
+       }
+       fscache_stat_d(&fscache_n_cop_grab_object);
+       spin_unlock(&parent->lock);
+       if (!success) {
+               _leave(" [grab failed]");
+               return transit_to(DETACH_FROM_COOKIE);
        }
 
-       spin_unlock(&object->cookie->parent->lock);
-       spin_unlock(&object->cookie->lock);
+       /* fscache_acquire_non_index_cookie() uses this
+        * to wake the chain up */
+       fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
+       _leave(" [wait]");
+       return transit_to(WAIT_FOR_PARENT);
+}
+
+/*
+ * Once the parent object is ready, we should kick off our lookup op.
+ */
+static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
+                                                       int event)
+{
+       struct fscache_object *parent = object->parent;
+
+       _enter("{OBJ%x},%d", object->debug_id, event);
+
+       ASSERT(parent != NULL);
+
+       spin_lock(&parent->lock);
+       parent->n_ops++;
+       parent->n_obj_ops++;
+       object->lookup_jif = jiffies;
+       spin_unlock(&parent->lock);
+
        _leave("");
+       return transit_to(LOOK_UP_OBJECT);
 }
 
 /*
@@ -503,15 +441,17 @@ static void fscache_initialise_object(struct fscache_object *object)
  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
  *   leaf-most cookies of the object and all its children
  */
-static void fscache_lookup_object(struct fscache_object *object)
+static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
+                                                         int event)
 {
        struct fscache_cookie *cookie = object->cookie;
-       struct fscache_object *parent;
+       struct fscache_object *parent = object->parent;
        int ret;
 
-       _enter("");
+       _enter("{OBJ%x},%d", object->debug_id, event);
+
+       object->oob_table = fscache_osm_lookup_oob;
 
-       parent = object->parent;
        ASSERT(parent != NULL);
        ASSERTCMP(parent->n_ops, >, 0);
        ASSERTCMP(parent->n_obj_ops, >, 0);
@@ -521,10 +461,8 @@ static void fscache_lookup_object(struct fscache_object *object)
 
        if (fscache_object_is_dying(parent) ||
            test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
-               _debug("unavailable");
-               set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
-               _leave("");
-               return;
+               _leave(" [unavailable]");
+               return transit_to(LOOKUP_FAILURE);
        }
 
        _debug("LOOKUP \"%s/%s\" in \"%s\"",
@@ -543,10 +481,17 @@ static void fscache_lookup_object(struct fscache_object *object)
                /* probably stuck behind another object, so move this one to
                 * the back of the queue */
                fscache_stat(&fscache_n_object_lookups_timed_out);
-               set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
+               _leave(" [timeout]");
+               return NO_TRANSIT;
        }
 
-       _leave("");
+       if (ret < 0) {
+               _leave(" [error]");
+               return transit_to(LOOKUP_FAILURE);
+       }
+
+       _leave(" [ok]");
+       return transit_to(OBJECT_AVAILABLE);
 }
 
 /**
@@ -560,32 +505,20 @@ void fscache_object_lookup_negative(struct fscache_object *object)
 {
        struct fscache_cookie *cookie = object->cookie;
 
-       _enter("{OBJ%x,%s}",
-              object->debug_id, fscache_object_states[object->state]);
+       _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 
-       spin_lock(&object->lock);
-       if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
+       if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
                fscache_stat(&fscache_n_object_lookups_negative);
 
-               /* transit here to allow write requests to begin stacking up
-                * and read requests to begin returning ENODATA */
-               object->state = FSCACHE_OBJECT_CREATING;
-               spin_unlock(&object->lock);
-
-               set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
+               /* Allow write requests to begin stacking up and read requests to begin
+                * returning ENODATA.
+                */
                set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 
                _debug("wake up lookup %p", &cookie->flags);
-               smp_mb__before_clear_bit();
-               clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
-               smp_mb__after_clear_bit();
+               clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
                wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
-               set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
-       } else {
-               ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
-               spin_unlock(&object->lock);
        }
-
        _leave("");
 }
 EXPORT_SYMBOL(fscache_object_lookup_negative);
@@ -604,37 +537,30 @@ void fscache_obtained_object(struct fscache_object *object)
 {
        struct fscache_cookie *cookie = object->cookie;
 
-       _enter("{OBJ%x,%s}",
-              object->debug_id, fscache_object_states[object->state]);
+       _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 
        /* if we were still looking up, then we must have a positive lookup
         * result, in which case there may be data available */
-       spin_lock(&object->lock);
-       if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
+       if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
                fscache_stat(&fscache_n_object_lookups_positive);
 
-               clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
-
-               object->state = FSCACHE_OBJECT_AVAILABLE;
-               spin_unlock(&object->lock);
+               /* We do (presumably) have data */
+               clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 
-               smp_mb__before_clear_bit();
-               clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
-               smp_mb__after_clear_bit();
+               /* Allow write requests to begin stacking up and read requests
+                * to begin shovelling data.
+                */
+               clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
                wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
-               set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
        } else {
-               ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
                fscache_stat(&fscache_n_object_created);
-
-               object->state = FSCACHE_OBJECT_AVAILABLE;
-               spin_unlock(&object->lock);
-               set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
-               smp_wmb();
        }
 
-       if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
-               wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
+       set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
+
+       /* Permit __fscache_relinquish_cookie() to proceed */
+       clear_bit_unlock(FSCACHE_COOKIE_CREATING, &cookie->flags);
+       wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 
        _leave("");
 }
@@ -643,15 +569,18 @@ EXPORT_SYMBOL(fscache_obtained_object);
 /*
  * handle an object that has just become available
  */
-static void fscache_object_available(struct fscache_object *object)
+static const struct fscache_state *fscache_object_available(struct fscache_object *object,
+                                                           int event)
 {
-       _enter("{OBJ%x}", object->debug_id);
+       struct fscache_cookie *cookie = object->cookie;
+
+       _enter("{OBJ%x},%d", object->debug_id, event);
+
+       object->oob_table = fscache_osm_run_oob;
 
        spin_lock(&object->lock);
 
-       if (object->cookie &&
-           test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
-               wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
+       ASSERTIF(cookie, !test_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags));
 
        fscache_done_parent_op(object);
        if (object->n_in_progress == 0) {
@@ -667,72 +596,117 @@ static void fscache_object_available(struct fscache_object *object)
        fscache_stat(&fscache_n_cop_lookup_complete);
        object->cache->ops->lookup_complete(object);
        fscache_stat_d(&fscache_n_cop_lookup_complete);
-       fscache_enqueue_dependents(object);
 
        fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
        fscache_stat(&fscache_n_object_avail);
 
        _leave("");
+       return transit_to(JUMPSTART_DEPS);
 }
 
 /*
- * drop an object's attachments
+ * Wake up this object's dependent objects now that we've become available.
  */
-static void fscache_drop_object(struct fscache_object *object)
+static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
+                                                               int event)
 {
-       struct fscache_object *parent = object->parent;
-       struct fscache_cache *cache = object->cache;
+       _enter("{OBJ%x},%d", object->debug_id, event);
 
-       _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
+       if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
+               return NO_TRANSIT; /* Not finished; requeue */
+       return transit_to(WAIT_FOR_CMD);
+}
 
-       ASSERTCMP(object->cookie, ==, NULL);
-       ASSERT(hlist_unhashed(&object->cookie_link));
+/*
+ * Handle lookup or creation failute.
+ */
+static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
+                                                         int event)
+{
+       struct fscache_cookie *cookie;
+       bool wake_looking_up = false;
 
-       spin_lock(&cache->object_list_lock);
-       list_del_init(&object->cache_link);
-       spin_unlock(&cache->object_list_lock);
+       _enter("{OBJ%x},%d", object->debug_id, event);
 
-       fscache_stat(&fscache_n_cop_drop_object);
-       cache->ops->drop_object(object);
-       fscache_stat_d(&fscache_n_cop_drop_object);
+       object->oob_event_mask = 0;
 
-       if (parent) {
-               _debug("release parent OBJ%x {%d}",
-                      parent->debug_id, parent->n_children);
+       fscache_stat(&fscache_n_cop_lookup_complete);
+       object->cache->ops->lookup_complete(object);
+       fscache_stat_d(&fscache_n_cop_lookup_complete);
 
-               spin_lock(&parent->lock);
-               parent->n_children--;
-               if (parent->n_children == 0)
-                       fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
-               spin_unlock(&parent->lock);
-               object->parent = NULL;
+       spin_lock(&object->lock);
+       cookie = object->cookie;
+       set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
+       if (cookie) {
+               if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
+                       wake_looking_up = true;
+               clear_bit_unlock(FSCACHE_COOKIE_CREATING, &cookie->flags);
        }
+       spin_unlock(&object->lock);
 
-       /* this just shifts the object release to the work processor */
-       fscache_put_object(object);
+       if (wake_looking_up)
+               wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
+       wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 
-       _leave("");
+       fscache_done_parent_op(object);
+       return transit_to(KILL_OBJECT);
+}
+
+/*
+ * Wait for completion of all active operations on this object and the death of
+ * all child objects of this object.
+ */
+static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
+                                                      int event)
+{
+       _enter("{OBJ%x,%d,%d},%d",
+              object->debug_id, object->n_ops, object->n_children, event);
+
+       object->oob_event_mask = 0;
+
+       spin_lock(&object->lock);
+       clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
+       spin_unlock(&object->lock);
+
+       if (list_empty(&object->dependents) &&
+           object->n_ops == 0 &&
+           object->n_children == 0)
+               return object->cookie ?
+                       transit_to(DETACH_FROM_COOKIE) : transit_to(DROP_OBJECT);
+
+       spin_lock(&object->lock);
+       fscache_start_operations(object);
+       spin_unlock(&object->lock);
+
+       if (!list_empty(&object->dependents))
+               return transit_to(KILL_DEPENDENTS);
+
+       return transit_to(WAIT_FOR_CLEARANCE);
 }
 
 /*
- * release or recycle an object that the netfs has discarded
+ * Kill dependent objects.
  */
-static void fscache_release_object(struct fscache_object *object)
+static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
+                                                          int event)
 {
-       _enter("");
+       _enter("{OBJ%x},%d", object->debug_id, event);
 
-       fscache_drop_object(object);
+       if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
+               return NO_TRANSIT; /* Not finished */
+       return transit_to(WAIT_FOR_CLEARANCE);
 }
 
 /*
  * withdraw an object from active service
  */
-static void fscache_withdraw_object(struct fscache_object *object)
+static const struct fscache_state *fscache_detach_from_cookie(struct fscache_object *object,
+                                                             int event)
 {
        struct fscache_cookie *cookie;
-       bool detached;
+       bool detached = false, awaken = false;
 
-       _enter("");
+       _enter("{OBJ%x},%d", object->debug_id, event);
 
        spin_lock(&object->lock);
        cookie = object->cookie;
@@ -742,14 +716,15 @@ static void fscache_withdraw_object(struct fscache_object *object)
                atomic_inc(&cookie->usage);
                spin_unlock(&object->lock);
 
-               detached = false;
                spin_lock(&cookie->lock);
                spin_lock(&object->lock);
 
                if (object->cookie == cookie) {
                        hlist_del_init(&object->cookie_link);
                        object->cookie = NULL;
-                       fscache_invalidation_complete(cookie);
+                       if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING,
+                                              &cookie->flags))
+                               awaken = true;
                        detached = true;
                }
                spin_unlock(&cookie->lock);
@@ -760,37 +735,62 @@ static void fscache_withdraw_object(struct fscache_object *object)
 
        spin_unlock(&object->lock);
 
-       fscache_drop_object(object);
+       if (awaken)
+               wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
+
+       fscache_stat(&fscache_n_object_dead);
+       _leave("");
+       return transit_to(DROP_OBJECT);
 }
 
 /*
- * withdraw an object from active service at the behest of the cache
- * - need break the links to a cached object cookie
- * - called under two situations:
- *   (1) recycler decides to reclaim an in-use object
- *   (2) a cache is unmounted
- * - have to take care as the cookie can be being relinquished by the netfs
- *   simultaneously
- * - the object is pinned by the caller holding a refcount on it
- */
-void fscache_withdrawing_object(struct fscache_cache *cache,
-                               struct fscache_object *object)
+ * Drop an object's attachments
+ */
+static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
+                                                      int event)
 {
-       bool enqueue = false;
+       struct fscache_object *parent = object->parent;
+       struct fscache_cache *cache = object->cache;
 
-       _enter(",OBJ%x", object->debug_id);
+       _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 
+       ASSERTCMP(object->cookie, ==, NULL);
+       ASSERT(hlist_unhashed(&object->cookie_link));
+
+       /* Prevent a race with our last child, which has to signal EV_CLEARED
+        * before dropping our spinlock.
+        */
        spin_lock(&object->lock);
-       if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
-               object->state = FSCACHE_OBJECT_WITHDRAWING;
-               enqueue = true;
-       }
        spin_unlock(&object->lock);
 
-       if (enqueue)
-               fscache_enqueue_object(object);
+       /* Discard from the cache's collection of objects */
+       spin_lock(&cache->object_list_lock);
+       list_del_init(&object->cache_link);
+       spin_unlock(&cache->object_list_lock);
+
+       fscache_stat(&fscache_n_cop_drop_object);
+       cache->ops->drop_object(object);
+       fscache_stat_d(&fscache_n_cop_drop_object);
+
+       /* The parent object wants to know when all it dependents have gone */
+       if (parent) {
+               _debug("release parent OBJ%x {%d}",
+                      parent->debug_id, parent->n_children);
+
+               spin_lock(&parent->lock);
+               parent->n_children--;
+               if (parent->n_children == 0)
+                       fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
+               spin_unlock(&parent->lock);
+               object->parent = NULL;
+       }
+
+       /* this just shifts the object release to the work processor */
+       fscache_put_object(object);
+       fscache_stat(&fscache_n_object_dead);
 
        _leave("");
+       return transit_to(OBJECT_DEAD);
 }
 
 /*
@@ -807,7 +807,7 @@ static int fscache_get_object(struct fscache_object *object)
 }
 
 /*
- * discard a ref on a work item
+ * Discard a ref on an object
  */
 static void fscache_put_object(struct fscache_object *object)
 {
@@ -839,7 +839,7 @@ void fscache_enqueue_object(struct fscache_object *object)
 
 /**
  * fscache_object_sleep_till_congested - Sleep until object wq is congested
- * @timoutp: Scheduler sleep timeout
+ * @timeoutp: Scheduler sleep timeout
  *
  * Allow an object handler to sleep until the object workqueue is congested.
  *
@@ -867,18 +867,21 @@ bool fscache_object_sleep_till_congested(signed long *timeoutp)
 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 
 /*
- * enqueue the dependents of an object for metadata-type processing
- * - the caller must hold the object's lock
- * - this may cause an already locked object to wind up being processed again
+ * Enqueue the dependents of an object for metadata-type processing.
+ *
+ * If we don't manage to finish the list before the scheduler wants to run
+ * again then return false immediately.  We return true if the list was
+ * cleared.
  */
-static void fscache_enqueue_dependents(struct fscache_object *object)
+static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 {
        struct fscache_object *dep;
+       bool ret = true;
 
        _enter("{OBJ%x}", object->debug_id);
 
        if (list_empty(&object->dependents))
-               return;
+               return true;
 
        spin_lock(&object->lock);
 
@@ -887,23 +890,23 @@ static void fscache_enqueue_dependents(struct fscache_object *object)
                                 struct fscache_object, dep_link);
                list_del_init(&dep->dep_link);
 
-
-               /* sort onto appropriate lists */
-               fscache_enqueue_object(dep);
+               fscache_raise_event(dep, event);
                fscache_put_object(dep);
 
-               if (!list_empty(&object->dependents))
-                       cond_resched_lock(&object->lock);
+               if (!list_empty(&object->dependents) && need_resched()) {
+                       ret = false;
+                       break;
+               }
        }
 
        spin_unlock(&object->lock);
+       return ret;
 }
 
 /*
  * remove an object from whatever queue it's waiting on
- * - the caller must hold object->lock
  */
-void fscache_dequeue_object(struct fscache_object *object)
+static void fscache_dequeue_object(struct fscache_object *object)
 {
        _enter("{OBJ%x}", object->debug_id);
 
@@ -963,12 +966,14 @@ EXPORT_SYMBOL(fscache_check_aux);
 /*
  * Asynchronously invalidate an object.
  */
-static void fscache_invalidate_object(struct fscache_object *object)
+static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
+                                                             int event)
 {
        struct fscache_operation *op;
        struct fscache_cookie *cookie = object->cookie;
 
-       _enter("{OBJ%x}", object->debug_id);
+       _enter("{OBJ%x},%d", object->debug_id, event);
+
 
        /* Reject any new read/write ops and abort any that are pending. */
        fscache_invalidate_writes(cookie);
@@ -978,9 +983,9 @@ static void fscache_invalidate_object(struct fscache_object *object)
        /* Now we have to wait for in-progress reads and writes */
        op = kzalloc(sizeof(*op), GFP_KERNEL);
        if (!op) {
-               fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
+               clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
                _leave(" [ENOMEM]");
-               return;
+               return transit_to(KILL_OBJECT);
        }
 
        fscache_operation_init(op, object->cache->ops->invalidate_object, NULL);
@@ -1001,13 +1006,44 @@ static void fscache_invalidate_object(struct fscache_object *object)
        /* We can allow read and write requests to come in once again.  They'll
         * queue up behind our exclusive invalidation operation.
         */
-       fscache_invalidation_complete(cookie);
-       _leave("");
-       return;
+       if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
+               wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
+       _leave(" [ok]");
+       return transit_to(UPDATE_OBJECT);
 
 submit_op_failed:
+       clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
        spin_unlock(&cookie->lock);
        kfree(op);
-       fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
        _leave(" [EIO]");
+       return transit_to(KILL_OBJECT);
+}
+
+static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
+                                                            int event)
+{
+       const struct fscache_state *s;
+
+       fscache_stat(&fscache_n_invalidates_run);
+       fscache_stat(&fscache_n_cop_invalidate_object);
+       s = _fscache_invalidate_object(object, event);
+       fscache_stat_d(&fscache_n_cop_invalidate_object);
+       return s;
+}
+
+/*
+ * Asynchronously update an object.
+ */
+static const struct fscache_state *fscache_update_object(struct fscache_object *object,
+                                                        int event)
+{
+       _enter("{OBJ%x},%d", object->debug_id, event);
+
+       fscache_stat(&fscache_n_updates_run);
+       fscache_stat(&fscache_n_cop_update_object);
+       object->cache->ops->update_object(object);
+       fscache_stat_d(&fscache_n_cop_update_object);
+
+       _leave("");
+       return transit_to(WAIT_FOR_CMD);
 }