diff options
Diffstat (limited to 'fs/fscache/object.c')
| -rw-r--r-- | fs/fscache/object.c | 1018 |
1 files changed, 1018 insertions, 0 deletions
diff --git a/fs/fscache/object.c b/fs/fscache/object.c new file mode 100644 index 000000000..da032daf0 --- /dev/null +++ b/fs/fscache/object.c @@ -0,0 +1,1018 @@ +/* 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); + +#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", (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 } +}; + +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 bool fscache_enqueue_dependents(struct fscache_object *, int); +static void fscache_dequeue_object(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; + 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); + 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; + } + } + } + + /* 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; + } + } + + /* 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); + + 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; + } + + _debug("{OBJ%x} %s -> %s", + object->debug_id, state->name, new_state->name); + object->state = state = new_state; + + if (state->work) { + if (unlikely(state->work == ((void *)2UL))) { + _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_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; + 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); + +/* + * 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)) { + 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); + + 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); + + clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags); + object->oob_event_mask = 0; + + 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)); + + /* 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); + + /* 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_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) +{ + int ret; + + fscache_stat(&fscache_n_cop_grab_object); + ret = object->cache->ops->grab_object(object) ? 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) +{ + fscache_stat(&fscache_n_cop_put_object); + object->cache->ops->put_object(object); + 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); + 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) >= 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); + + 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); + + 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) +{ + 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); + 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(object->cookie->stores.rnode == NULL); + 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(op, object->cache->ops->invalidate_object, NULL); + op->flags = FSCACHE_OP_ASYNC | + (1 << FSCACHE_OP_EXCLUSIVE) | + (1 << FSCACHE_OP_UNUSE_COOKIE); + + 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: + clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags); + fscache_unuse_cookie(object); + _leave(" [ENOMEM]"); + return transit_to(KILL_OBJECT); + +submit_op_failed: + clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags); + 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; +} + +/* + * 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); +} |