v4.19.13 snapshot.
diff --git a/fs/fscache/object.c b/fs/fscache/object.c
new file mode 100644
index 0000000..6d9cb17
--- /dev/null
+++ b/fs/fscache/object.c
@@ -0,0 +1,1137 @@
+/* FS-Cache object state machine handler
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * See Documentation/filesystems/caching/object.txt for a description of the
+ * object state machine and the in-kernel representations.
+ */
+
+#define FSCACHE_DEBUG_LEVEL COOKIE
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/prefetch.h>
+#include "internal.h"
+
+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_object_dead(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(OBJECT_DEAD, "DEAD", fscache_object_dead);
+
+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 }
+};
+
+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 *,
+ enum fscache_obj_ref_trace);
+static void fscache_put_object(struct fscache_object *,
+ enum fscache_obj_ref_trace);
+static bool fscache_enqueue_dependents(struct fscache_object *, int);
+static void fscache_dequeue_object(struct fscache_object *);
+static void fscache_update_aux_data(struct fscache_object *);
+
+/*
+ * we need to notify the parent when an op completes that we had outstanding
+ * upon it
+ */
+static inline void fscache_done_parent_op(struct fscache_object *object)
+{
+ struct fscache_object *parent = object->parent;
+
+ _enter("OBJ%x {OBJ%x,%x}",
+ object->debug_id, parent->debug_id, parent->n_ops);
+
+ spin_lock_nested(&parent->lock, 1);
+ parent->n_obj_ops--;
+ parent->n_ops--;
+ if (parent->n_ops == 0)
+ fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
+ spin_unlock(&parent->lock);
+}
+
+/*
+ * Object state machine dispatcher.
+ */
+static void fscache_object_sm_dispatcher(struct fscache_object *object)
+{
+ const struct fscache_transition *t;
+ const struct fscache_state *state, *new_state;
+ unsigned long events, event_mask;
+ bool oob;
+ int event = -1;
+
+ ASSERT(object != NULL);
+
+ _enter("{OBJ%x,%s,%lx}",
+ 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);
+ oob = true;
+ 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;
+ }
+ }
+ }
+ oob = false;
+
+ /* 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;
+ trace_fscache_osm(object, state,
+ true, false, event);
+ 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;
+ }
+ }
+
+ /* The event mask didn't include all the tabled bits */
+ BUG();
+ }
+ /* Randomly woke up */
+ goto unmask_events;
+ }
+
+execute_work_state:
+ _debug("{OBJ%x} exec %s", object->debug_id, state->name);
+
+ trace_fscache_osm(object, state, false, oob, event);
+ new_state = state->work(object, event);
+ event = -1;
+ if (new_state == NO_TRANSIT) {
+ _debug("{OBJ%x} %s notrans", object->debug_id, state->name);
+ if (unlikely(state == STATE(OBJECT_DEAD))) {
+ _leave(" [dead]");
+ return;
+ }
+ fscache_enqueue_object(object);
+ event_mask = object->oob_event_mask;
+ goto unmask_events;
+ }
+
+ _debug("{OBJ%x} %s -> %s",
+ object->debug_id, state->name, new_state->name);
+ object->state = state = new_state;
+
+ if (state->work) {
+ if (unlikely(state == STATE(OBJECT_DEAD))) {
+ _leave(" [dead]");
+ return;
+ }
+ goto restart_masked;
+ }
+
+ /* 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);
+}
+
+/*
+ * execute an object
+ */
+static void fscache_object_work_func(struct work_struct *work)
+{
+ struct fscache_object *object =
+ container_of(work, struct fscache_object, work);
+ unsigned long start;
+
+ _enter("{OBJ%x}", object->debug_id);
+
+ start = jiffies;
+ fscache_object_sm_dispatcher(object);
+ fscache_hist(fscache_objs_histogram, start);
+ fscache_put_object(object, fscache_obj_put_work);
+}
+
+/**
+ * fscache_object_init - Initialise a cache object description
+ * @object: Object description
+ * @cookie: Cookie object will be attached to
+ * @cache: Cache in which backing object will be found
+ *
+ * Initialise a cache object description to its basic values.
+ *
+ * See Documentation/filesystems/caching/backend-api.txt for a complete
+ * description.
+ */
+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 = 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);
+ INIT_WORK(&object->work, fscache_object_work_func);
+ INIT_LIST_HEAD(&object->dependents);
+ INIT_LIST_HEAD(&object->dep_link);
+ INIT_LIST_HEAD(&object->pending_ops);
+ object->n_children = 0;
+ object->n_ops = object->n_in_progress = object->n_exclusive = 0;
+ object->events = 0;
+ object->store_limit = 0;
+ object->store_limit_l = 0;
+ object->cache = cache;
+ object->cookie = cookie;
+ fscache_cookie_get(cookie, fscache_cookie_get_attach_object);
+ object->parent = NULL;
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+ RB_CLEAR_NODE(&object->objlist_link);
+#endif
+
+ 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);
+
+/*
+ * Mark the object as no longer being live, making sure that we synchronise
+ * against op submission.
+ */
+static inline void fscache_mark_object_dead(struct fscache_object *object)
+{
+ spin_lock(&object->lock);
+ clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
+ spin_unlock(&object->lock);
+}
+
+/*
+ * Abort object initialisation before we start it.
+ */
+static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
+ int event)
+{
+ _enter("{OBJ%x},%d", object->debug_id, event);
+
+ object->oob_event_mask = 0;
+ fscache_dequeue_object(object);
+ return transit_to(KILL_OBJECT);
+}
+
+/*
+ * initialise an object
+ * - check the specified object's parent to see if we can make use of it
+ * immediately to do a creation
+ * - we may need to start the process of creating a parent and we need to wait
+ * for the parent's lookup and creation to complete if it's not there yet
+ */
+static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
+ int event)
+{
+ struct fscache_object *parent;
+ bool success;
+
+ _enter("{OBJ%x},%d", object->debug_id, event);
+
+ ASSERT(list_empty(&object->dep_link));
+
+ parent = object->parent;
+ if (!parent) {
+ _leave(" [no parent]");
+ return transit_to(DROP_OBJECT);
+ }
+
+ _debug("parent: %s of:%lx", parent->state->name, parent->flags);
+
+ if (fscache_object_is_dying(parent)) {
+ _leave(" [bad parent]");
+ return transit_to(DROP_OBJECT);
+ }
+
+ 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, fscache_obj_get_add_to_deps)) {
+ 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(DROP_OBJECT);
+ }
+
+ /* 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);
+}
+
+/*
+ * look an object up in the cache from which it was allocated
+ * - we hold an "access lock" on the parent object, so the parent object cannot
+ * be withdrawn by either party till we've finished
+ */
+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 = object->parent;
+ int ret;
+
+ _enter("{OBJ%x},%d", object->debug_id, event);
+
+ object->oob_table = fscache_osm_lookup_oob;
+
+ ASSERT(parent != NULL);
+ ASSERTCMP(parent->n_ops, >, 0);
+ ASSERTCMP(parent->n_obj_ops, >, 0);
+
+ /* make sure the parent is still available */
+ ASSERT(fscache_object_is_available(parent));
+
+ if (fscache_object_is_dying(parent) ||
+ test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
+ !fscache_use_cookie(object)) {
+ _leave(" [unavailable]");
+ return transit_to(LOOKUP_FAILURE);
+ }
+
+ _debug("LOOKUP \"%s\" in \"%s\"",
+ cookie->def->name, object->cache->tag->name);
+
+ fscache_stat(&fscache_n_object_lookups);
+ fscache_stat(&fscache_n_cop_lookup_object);
+ ret = object->cache->ops->lookup_object(object);
+ fscache_stat_d(&fscache_n_cop_lookup_object);
+
+ fscache_unuse_cookie(object);
+
+ if (ret == -ETIMEDOUT) {
+ /* probably stuck behind another object, so move this one to
+ * the back of the queue */
+ fscache_stat(&fscache_n_object_lookups_timed_out);
+ _leave(" [timeout]");
+ return NO_TRANSIT;
+ }
+
+ if (ret < 0) {
+ _leave(" [error]");
+ return transit_to(LOOKUP_FAILURE);
+ }
+
+ _leave(" [ok]");
+ return transit_to(OBJECT_AVAILABLE);
+}
+
+/**
+ * fscache_object_lookup_negative - Note negative cookie lookup
+ * @object: Object pointing to cookie to mark
+ *
+ * Note negative lookup, permitting those waiting to read data from an already
+ * existing backing object to continue as there's no data for them to read.
+ */
+void fscache_object_lookup_negative(struct fscache_object *object)
+{
+ struct fscache_cookie *cookie = object->cookie;
+
+ _enter("{OBJ%x,%s}", object->debug_id, object->state->name);
+
+ if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
+ fscache_stat(&fscache_n_object_lookups_negative);
+
+ /* Allow write requests to begin stacking up and read requests to begin
+ * returning ENODATA.
+ */
+ set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
+ clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
+
+ _debug("wake up lookup %p", &cookie->flags);
+ clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
+ wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
+ }
+ _leave("");
+}
+EXPORT_SYMBOL(fscache_object_lookup_negative);
+
+/**
+ * fscache_obtained_object - Note successful object lookup or creation
+ * @object: Object pointing to cookie to mark
+ *
+ * Note successful lookup and/or creation, permitting those waiting to write
+ * data to a backing object to continue.
+ *
+ * Note that after calling this, an object's cookie may be relinquished by the
+ * netfs, and so must be accessed with object lock held.
+ */
+void fscache_obtained_object(struct fscache_object *object)
+{
+ struct fscache_cookie *cookie = object->cookie;
+
+ _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 */
+ if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
+ fscache_stat(&fscache_n_object_lookups_positive);
+
+ /* We do (presumably) have data */
+ clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
+ clear_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
+
+ /* 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);
+ } else {
+ fscache_stat(&fscache_n_object_created);
+ }
+
+ set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
+ _leave("");
+}
+EXPORT_SYMBOL(fscache_obtained_object);
+
+/*
+ * handle an object that has just become available
+ */
+static const struct fscache_state *fscache_object_available(struct fscache_object *object,
+ int event)
+{
+ _enter("{OBJ%x},%d", object->debug_id, event);
+
+ object->oob_table = fscache_osm_run_oob;
+
+ spin_lock(&object->lock);
+
+ fscache_done_parent_op(object);
+ if (object->n_in_progress == 0) {
+ if (object->n_ops > 0) {
+ ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
+ fscache_start_operations(object);
+ } else {
+ ASSERT(list_empty(&object->pending_ops));
+ }
+ }
+ spin_unlock(&object->lock);
+
+ fscache_stat(&fscache_n_cop_lookup_complete);
+ object->cache->ops->lookup_complete(object);
+ fscache_stat_d(&fscache_n_cop_lookup_complete);
+
+ fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
+ fscache_stat(&fscache_n_object_avail);
+
+ _leave("");
+ return transit_to(JUMPSTART_DEPS);
+}
+
+/*
+ * Wake up this object's dependent objects now that we've become available.
+ */
+static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
+ int event)
+{
+ _enter("{OBJ%x},%d", object->debug_id, event);
+
+ if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
+ return NO_TRANSIT; /* Not finished; requeue */
+ return transit_to(WAIT_FOR_CMD);
+}
+
+/*
+ * Handle lookup or creation failute.
+ */
+static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
+ int event)
+{
+ struct fscache_cookie *cookie;
+
+ _enter("{OBJ%x},%d", object->debug_id, event);
+
+ object->oob_event_mask = 0;
+
+ fscache_stat(&fscache_n_cop_lookup_complete);
+ object->cache->ops->lookup_complete(object);
+ fscache_stat_d(&fscache_n_cop_lookup_complete);
+
+ set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags);
+
+ cookie = object->cookie;
+ set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
+ if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
+ wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
+
+ 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);
+
+ fscache_mark_object_dead(object);
+ object->oob_event_mask = 0;
+
+ if (test_bit(FSCACHE_OBJECT_RETIRED, &object->flags)) {
+ /* Reject any new read/write ops and abort any that are pending. */
+ clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
+ fscache_cancel_all_ops(object);
+ }
+
+ if (list_empty(&object->dependents) &&
+ object->n_ops == 0 &&
+ object->n_children == 0)
+ return transit_to(DROP_OBJECT);
+
+ if (object->n_in_progress == 0) {
+ spin_lock(&object->lock);
+ if (object->n_ops > 0 && object->n_in_progress == 0)
+ fscache_start_operations(object);
+ spin_unlock(&object->lock);
+ }
+
+ if (!list_empty(&object->dependents))
+ return transit_to(KILL_DEPENDENTS);
+
+ return transit_to(WAIT_FOR_CLEARANCE);
+}
+
+/*
+ * Kill dependent objects.
+ */
+static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
+ int event)
+{
+ _enter("{OBJ%x},%d", object->debug_id, event);
+
+ if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
+ return NO_TRANSIT; /* Not finished */
+ return transit_to(WAIT_FOR_CLEARANCE);
+}
+
+/*
+ * Drop an object's attachments
+ */
+static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
+ int event)
+{
+ struct fscache_object *parent = object->parent;
+ struct fscache_cookie *cookie = object->cookie;
+ struct fscache_cache *cache = object->cache;
+ bool awaken = false;
+
+ _enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
+
+ ASSERT(cookie != NULL);
+ ASSERT(!hlist_unhashed(&object->cookie_link));
+
+ if (test_bit(FSCACHE_COOKIE_AUX_UPDATED, &cookie->flags)) {
+ _debug("final update");
+ fscache_update_aux_data(object);
+ }
+
+ /* Make sure the cookie no longer points here and that the netfs isn't
+ * waiting for us.
+ */
+ spin_lock(&cookie->lock);
+ hlist_del_init(&object->cookie_link);
+ if (hlist_empty(&cookie->backing_objects) &&
+ test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
+ awaken = true;
+ spin_unlock(&cookie->lock);
+
+ if (awaken)
+ wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
+ if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
+ wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
+
+
+ /* Prevent a race with our last child, which has to signal EV_CLEARED
+ * before dropping our spinlock.
+ */
+ spin_lock(&object->lock);
+ spin_unlock(&object->lock);
+
+ /* 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_obj_put_drop_obj);
+ fscache_stat(&fscache_n_object_dead);
+
+ _leave("");
+ return transit_to(OBJECT_DEAD);
+}
+
+/*
+ * get a ref on an object
+ */
+static int fscache_get_object(struct fscache_object *object,
+ enum fscache_obj_ref_trace why)
+{
+ int ret;
+
+ fscache_stat(&fscache_n_cop_grab_object);
+ ret = object->cache->ops->grab_object(object, why) ? 0 : -EAGAIN;
+ fscache_stat_d(&fscache_n_cop_grab_object);
+ return ret;
+}
+
+/*
+ * Discard a ref on an object
+ */
+static void fscache_put_object(struct fscache_object *object,
+ enum fscache_obj_ref_trace why)
+{
+ fscache_stat(&fscache_n_cop_put_object);
+ object->cache->ops->put_object(object, why);
+ fscache_stat_d(&fscache_n_cop_put_object);
+}
+
+/**
+ * fscache_object_destroy - Note that a cache object is about to be destroyed
+ * @object: The object to be destroyed
+ *
+ * Note the imminent destruction and deallocation of a cache object record.
+ */
+void fscache_object_destroy(struct fscache_object *object)
+{
+ fscache_objlist_remove(object);
+
+ /* We can get rid of the cookie now */
+ fscache_cookie_put(object->cookie, fscache_cookie_put_object);
+ object->cookie = NULL;
+}
+EXPORT_SYMBOL(fscache_object_destroy);
+
+/*
+ * enqueue an object for metadata-type processing
+ */
+void fscache_enqueue_object(struct fscache_object *object)
+{
+ _enter("{OBJ%x}", object->debug_id);
+
+ if (fscache_get_object(object, fscache_obj_get_queue) >= 0) {
+ wait_queue_head_t *cong_wq =
+ &get_cpu_var(fscache_object_cong_wait);
+
+ if (queue_work(fscache_object_wq, &object->work)) {
+ if (fscache_object_congested())
+ wake_up(cong_wq);
+ } else
+ fscache_put_object(object, fscache_obj_put_queue);
+
+ put_cpu_var(fscache_object_cong_wait);
+ }
+}
+
+/**
+ * fscache_object_sleep_till_congested - Sleep until object wq is congested
+ * @timeoutp: Scheduler sleep timeout
+ *
+ * Allow an object handler to sleep until the object workqueue is congested.
+ *
+ * The caller must set up a wake up event before calling this and must have set
+ * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
+ * condition before calling this function as no test is made here.
+ *
+ * %true is returned if the object wq is congested, %false otherwise.
+ */
+bool fscache_object_sleep_till_congested(signed long *timeoutp)
+{
+ wait_queue_head_t *cong_wq = this_cpu_ptr(&fscache_object_cong_wait);
+ DEFINE_WAIT(wait);
+
+ if (fscache_object_congested())
+ return true;
+
+ add_wait_queue_exclusive(cong_wq, &wait);
+ if (!fscache_object_congested())
+ *timeoutp = schedule_timeout(*timeoutp);
+ finish_wait(cong_wq, &wait);
+
+ return fscache_object_congested();
+}
+EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
+
+/*
+ * 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 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 true;
+
+ spin_lock(&object->lock);
+
+ while (!list_empty(&object->dependents)) {
+ dep = list_entry(object->dependents.next,
+ struct fscache_object, dep_link);
+ list_del_init(&dep->dep_link);
+
+ fscache_raise_event(dep, event);
+ fscache_put_object(dep, fscache_obj_put_enq_dep);
+
+ 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
+ */
+static void fscache_dequeue_object(struct fscache_object *object)
+{
+ _enter("{OBJ%x}", object->debug_id);
+
+ if (!list_empty(&object->dep_link)) {
+ spin_lock(&object->parent->lock);
+ list_del_init(&object->dep_link);
+ spin_unlock(&object->parent->lock);
+ }
+
+ _leave("");
+}
+
+/**
+ * fscache_check_aux - Ask the netfs whether an object on disk is still valid
+ * @object: The object to ask about
+ * @data: The auxiliary data for the object
+ * @datalen: The size of the auxiliary data
+ *
+ * This function consults the netfs about the coherency state of an object.
+ * The caller must be holding a ref on cookie->n_active (held by
+ * fscache_look_up_object() on behalf of the cache backend during object lookup
+ * and creation).
+ */
+enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
+ const void *data, uint16_t datalen,
+ loff_t object_size)
+{
+ enum fscache_checkaux result;
+
+ if (!object->cookie->def->check_aux) {
+ fscache_stat(&fscache_n_checkaux_none);
+ return FSCACHE_CHECKAUX_OKAY;
+ }
+
+ result = object->cookie->def->check_aux(object->cookie->netfs_data,
+ data, datalen, object_size);
+ switch (result) {
+ /* entry okay as is */
+ case FSCACHE_CHECKAUX_OKAY:
+ fscache_stat(&fscache_n_checkaux_okay);
+ break;
+
+ /* entry requires update */
+ case FSCACHE_CHECKAUX_NEEDS_UPDATE:
+ fscache_stat(&fscache_n_checkaux_update);
+ break;
+
+ /* entry requires deletion */
+ case FSCACHE_CHECKAUX_OBSOLETE:
+ fscache_stat(&fscache_n_checkaux_obsolete);
+ break;
+
+ default:
+ BUG();
+ }
+
+ return result;
+}
+EXPORT_SYMBOL(fscache_check_aux);
+
+/*
+ * Asynchronously invalidate an 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},%d", object->debug_id, event);
+
+ /* We're going to need the cookie. If the cookie is not available then
+ * retire the object instead.
+ */
+ if (!fscache_use_cookie(object)) {
+ ASSERT(radix_tree_empty(&object->cookie->stores));
+ set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
+ _leave(" [no cookie]");
+ return transit_to(KILL_OBJECT);
+ }
+
+ /* Reject any new read/write ops and abort any that are pending. */
+ fscache_invalidate_writes(cookie);
+ clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
+ fscache_cancel_all_ops(object);
+
+ /* Now we have to wait for in-progress reads and writes */
+ op = kzalloc(sizeof(*op), GFP_KERNEL);
+ if (!op)
+ goto nomem;
+
+ fscache_operation_init(cookie, op, object->cache->ops->invalidate_object,
+ NULL, NULL);
+ op->flags = FSCACHE_OP_ASYNC |
+ (1 << FSCACHE_OP_EXCLUSIVE) |
+ (1 << FSCACHE_OP_UNUSE_COOKIE);
+ trace_fscache_page_op(cookie, NULL, op, fscache_page_op_invalidate);
+
+ spin_lock(&cookie->lock);
+ if (fscache_submit_exclusive_op(object, op) < 0)
+ goto submit_op_failed;
+ spin_unlock(&cookie->lock);
+ fscache_put_operation(op);
+
+ /* Once we've completed the invalidation, we know there will be no data
+ * stored in the cache and thus we can reinstate the data-check-skip
+ * optimisation.
+ */
+ set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
+
+ /* We can allow read and write requests to come in once again. They'll
+ * queue up behind our exclusive invalidation operation.
+ */
+ 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);
+
+nomem:
+ fscache_mark_object_dead(object);
+ fscache_unuse_cookie(object);
+ _leave(" [ENOMEM]");
+ return transit_to(KILL_OBJECT);
+
+submit_op_failed:
+ fscache_mark_object_dead(object);
+ spin_unlock(&cookie->lock);
+ fscache_unuse_cookie(object);
+ kfree(op);
+ _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;
+}
+
+/*
+ * Update auxiliary data.
+ */
+static void fscache_update_aux_data(struct fscache_object *object)
+{
+ 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);
+}
+
+/*
+ * 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_update_aux_data(object);
+
+ _leave("");
+ return transit_to(WAIT_FOR_CMD);
+}
+
+/**
+ * fscache_object_retrying_stale - Note retrying stale object
+ * @object: The object that will be retried
+ *
+ * Note that an object lookup found an on-disk object that was adjudged to be
+ * stale and has been deleted. The lookup will be retried.
+ */
+void fscache_object_retrying_stale(struct fscache_object *object)
+{
+ fscache_stat(&fscache_n_cache_no_space_reject);
+}
+EXPORT_SYMBOL(fscache_object_retrying_stale);
+
+/**
+ * fscache_object_mark_killed - Note that an object was killed
+ * @object: The object that was culled
+ * @why: The reason the object was killed.
+ *
+ * Note that an object was killed. Returns true if the object was
+ * already marked killed, false if it wasn't.
+ */
+void fscache_object_mark_killed(struct fscache_object *object,
+ enum fscache_why_object_killed why)
+{
+ if (test_and_set_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->flags)) {
+ pr_err("Error: Object already killed by cache [%s]\n",
+ object->cache->identifier);
+ return;
+ }
+
+ switch (why) {
+ case FSCACHE_OBJECT_NO_SPACE:
+ fscache_stat(&fscache_n_cache_no_space_reject);
+ break;
+ case FSCACHE_OBJECT_IS_STALE:
+ fscache_stat(&fscache_n_cache_stale_objects);
+ break;
+ case FSCACHE_OBJECT_WAS_RETIRED:
+ fscache_stat(&fscache_n_cache_retired_objects);
+ break;
+ case FSCACHE_OBJECT_WAS_CULLED:
+ fscache_stat(&fscache_n_cache_culled_objects);
+ break;
+ }
+}
+EXPORT_SYMBOL(fscache_object_mark_killed);
+
+/*
+ * The object is dead. We can get here if an object gets queued by an event
+ * that would lead to its death (such as EV_KILL) when the dispatcher is
+ * already running (and so can be requeued) but hasn't yet cleared the event
+ * mask.
+ */
+static const struct fscache_state *fscache_object_dead(struct fscache_object *object,
+ int event)
+{
+ if (!test_and_set_bit(FSCACHE_OBJECT_RUN_AFTER_DEAD,
+ &object->flags))
+ return NO_TRANSIT;
+
+ WARN(true, "FS-Cache object redispatched after death");
+ return NO_TRANSIT;
+}