linux-stable/fs/fscache/cookie.c
David Howells ef778e7ae6 FS-Cache: Provide proper invalidation
Provide a proper invalidation method rather than relying on the netfs retiring
the cookie it has and getting a new one.  The problem with this is that isn't
easy for the netfs to make sure that it has completed/cancelled all its
outstanding storage and retrieval operations on the cookie it is retiring.

Instead, have the cache provide an invalidation method that will cancel or wait
for all currently outstanding operations before invalidating the cache, and
will cause new operations to queue up behind that.  Whilst invalidation is in
progress, some requests will be rejected until the cache can stack a barrier on
the operation queue to cause new operations to be deferred behind it.

Signed-off-by: David Howells <dhowells@redhat.com>
2012-12-20 22:04:07 +00:00

592 lines
16 KiB
C

/* netfs cookie management
*
* Copyright (C) 2004-2007 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/netfs-api.txt for more information on
* the netfs API.
*/
#define FSCACHE_DEBUG_LEVEL COOKIE
#include <linux/module.h>
#include <linux/slab.h>
#include "internal.h"
struct kmem_cache *fscache_cookie_jar;
static atomic_t fscache_object_debug_id = ATOMIC_INIT(0);
static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie);
static int fscache_alloc_object(struct fscache_cache *cache,
struct fscache_cookie *cookie);
static int fscache_attach_object(struct fscache_cookie *cookie,
struct fscache_object *object);
/*
* initialise an cookie jar slab element prior to any use
*/
void fscache_cookie_init_once(void *_cookie)
{
struct fscache_cookie *cookie = _cookie;
memset(cookie, 0, sizeof(*cookie));
spin_lock_init(&cookie->lock);
spin_lock_init(&cookie->stores_lock);
INIT_HLIST_HEAD(&cookie->backing_objects);
}
/*
* request a cookie to represent an object (index, datafile, xattr, etc)
* - parent specifies the parent object
* - the top level index cookie for each netfs is stored in the fscache_netfs
* struct upon registration
* - def points to the definition
* - the netfs_data will be passed to the functions pointed to in *def
* - all attached caches will be searched to see if they contain this object
* - index objects aren't stored on disk until there's a dependent file that
* needs storing
* - other objects are stored in a selected cache immediately, and all the
* indices forming the path to it are instantiated if necessary
* - we never let on to the netfs about errors
* - we may set a negative cookie pointer, but that's okay
*/
struct fscache_cookie *__fscache_acquire_cookie(
struct fscache_cookie *parent,
const struct fscache_cookie_def *def,
void *netfs_data)
{
struct fscache_cookie *cookie;
BUG_ON(!def);
_enter("{%s},{%s},%p",
parent ? (char *) parent->def->name : "<no-parent>",
def->name, netfs_data);
fscache_stat(&fscache_n_acquires);
/* if there's no parent cookie, then we don't create one here either */
if (!parent) {
fscache_stat(&fscache_n_acquires_null);
_leave(" [no parent]");
return NULL;
}
/* validate the definition */
BUG_ON(!def->get_key);
BUG_ON(!def->name[0]);
BUG_ON(def->type == FSCACHE_COOKIE_TYPE_INDEX &&
parent->def->type != FSCACHE_COOKIE_TYPE_INDEX);
/* allocate and initialise a cookie */
cookie = kmem_cache_alloc(fscache_cookie_jar, GFP_KERNEL);
if (!cookie) {
fscache_stat(&fscache_n_acquires_oom);
_leave(" [ENOMEM]");
return NULL;
}
atomic_set(&cookie->usage, 1);
atomic_set(&cookie->n_children, 0);
atomic_inc(&parent->usage);
atomic_inc(&parent->n_children);
cookie->def = def;
cookie->parent = parent;
cookie->netfs_data = netfs_data;
cookie->flags = 0;
/* radix tree insertion won't use the preallocation pool unless it's
* told it may not wait */
INIT_RADIX_TREE(&cookie->stores, GFP_NOFS & ~__GFP_WAIT);
switch (cookie->def->type) {
case FSCACHE_COOKIE_TYPE_INDEX:
fscache_stat(&fscache_n_cookie_index);
break;
case FSCACHE_COOKIE_TYPE_DATAFILE:
fscache_stat(&fscache_n_cookie_data);
break;
default:
fscache_stat(&fscache_n_cookie_special);
break;
}
/* if the object is an index then we need do nothing more here - we
* create indices on disk when we need them as an index may exist in
* multiple caches */
if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
if (fscache_acquire_non_index_cookie(cookie) < 0) {
atomic_dec(&parent->n_children);
__fscache_cookie_put(cookie);
fscache_stat(&fscache_n_acquires_nobufs);
_leave(" = NULL");
return NULL;
}
}
fscache_stat(&fscache_n_acquires_ok);
_leave(" = %p", cookie);
return cookie;
}
EXPORT_SYMBOL(__fscache_acquire_cookie);
/*
* acquire a non-index cookie
* - this must make sure the index chain is instantiated and instantiate the
* object representation too
*/
static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie)
{
struct fscache_object *object;
struct fscache_cache *cache;
uint64_t i_size;
int ret;
_enter("");
cookie->flags = 1 << FSCACHE_COOKIE_UNAVAILABLE;
/* now we need to see whether the backing objects for this cookie yet
* exist, if not there'll be nothing to search */
down_read(&fscache_addremove_sem);
if (list_empty(&fscache_cache_list)) {
up_read(&fscache_addremove_sem);
_leave(" = 0 [no caches]");
return 0;
}
/* select a cache in which to store the object */
cache = fscache_select_cache_for_object(cookie->parent);
if (!cache) {
up_read(&fscache_addremove_sem);
fscache_stat(&fscache_n_acquires_no_cache);
_leave(" = -ENOMEDIUM [no cache]");
return -ENOMEDIUM;
}
_debug("cache %s", cache->tag->name);
cookie->flags =
(1 << FSCACHE_COOKIE_LOOKING_UP) |
(1 << FSCACHE_COOKIE_CREATING) |
(1 << FSCACHE_COOKIE_NO_DATA_YET);
/* ask the cache to allocate objects for this cookie and its parent
* chain */
ret = fscache_alloc_object(cache, cookie);
if (ret < 0) {
up_read(&fscache_addremove_sem);
_leave(" = %d", ret);
return ret;
}
/* pass on how big the object we're caching is supposed to be */
cookie->def->get_attr(cookie->netfs_data, &i_size);
spin_lock(&cookie->lock);
if (hlist_empty(&cookie->backing_objects)) {
spin_unlock(&cookie->lock);
goto unavailable;
}
object = hlist_entry(cookie->backing_objects.first,
struct fscache_object, cookie_link);
fscache_set_store_limit(object, i_size);
/* initiate the process of looking up all the objects in the chain
* (done by fscache_initialise_object()) */
fscache_enqueue_object(object);
spin_unlock(&cookie->lock);
/* we may be required to wait for lookup to complete at this point */
if (!fscache_defer_lookup) {
_debug("non-deferred lookup %p", &cookie->flags);
wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
fscache_wait_bit, TASK_UNINTERRUPTIBLE);
_debug("complete");
if (test_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags))
goto unavailable;
}
up_read(&fscache_addremove_sem);
_leave(" = 0 [deferred]");
return 0;
unavailable:
up_read(&fscache_addremove_sem);
_leave(" = -ENOBUFS");
return -ENOBUFS;
}
/*
* recursively allocate cache object records for a cookie/cache combination
* - caller must be holding the addremove sem
*/
static int fscache_alloc_object(struct fscache_cache *cache,
struct fscache_cookie *cookie)
{
struct fscache_object *object;
struct hlist_node *_n;
int ret;
_enter("%p,%p{%s}", cache, cookie, cookie->def->name);
spin_lock(&cookie->lock);
hlist_for_each_entry(object, _n, &cookie->backing_objects,
cookie_link) {
if (object->cache == cache)
goto object_already_extant;
}
spin_unlock(&cookie->lock);
/* ask the cache to allocate an object (we may end up with duplicate
* objects at this stage, but we sort that out later) */
fscache_stat(&fscache_n_cop_alloc_object);
object = cache->ops->alloc_object(cache, cookie);
fscache_stat_d(&fscache_n_cop_alloc_object);
if (IS_ERR(object)) {
fscache_stat(&fscache_n_object_no_alloc);
ret = PTR_ERR(object);
goto error;
}
fscache_stat(&fscache_n_object_alloc);
object->debug_id = atomic_inc_return(&fscache_object_debug_id);
_debug("ALLOC OBJ%x: %s {%lx}",
object->debug_id, cookie->def->name, object->events);
ret = fscache_alloc_object(cache, cookie->parent);
if (ret < 0)
goto error_put;
/* only attach if we managed to allocate all we needed, otherwise
* discard the object we just allocated and instead use the one
* attached to the cookie */
if (fscache_attach_object(cookie, object) < 0) {
fscache_stat(&fscache_n_cop_put_object);
cache->ops->put_object(object);
fscache_stat_d(&fscache_n_cop_put_object);
}
_leave(" = 0");
return 0;
object_already_extant:
ret = -ENOBUFS;
if (object->state >= FSCACHE_OBJECT_DYING) {
spin_unlock(&cookie->lock);
goto error;
}
spin_unlock(&cookie->lock);
_leave(" = 0 [found]");
return 0;
error_put:
fscache_stat(&fscache_n_cop_put_object);
cache->ops->put_object(object);
fscache_stat_d(&fscache_n_cop_put_object);
error:
_leave(" = %d", ret);
return ret;
}
/*
* attach a cache object to a cookie
*/
static int fscache_attach_object(struct fscache_cookie *cookie,
struct fscache_object *object)
{
struct fscache_object *p;
struct fscache_cache *cache = object->cache;
struct hlist_node *_n;
int ret;
_enter("{%s},{OBJ%x}", cookie->def->name, object->debug_id);
spin_lock(&cookie->lock);
/* there may be multiple initial creations of this object, but we only
* want one */
ret = -EEXIST;
hlist_for_each_entry(p, _n, &cookie->backing_objects, cookie_link) {
if (p->cache == object->cache) {
if (p->state >= FSCACHE_OBJECT_DYING)
ret = -ENOBUFS;
goto cant_attach_object;
}
}
/* pin the parent object */
spin_lock_nested(&cookie->parent->lock, 1);
hlist_for_each_entry(p, _n, &cookie->parent->backing_objects,
cookie_link) {
if (p->cache == object->cache) {
if (p->state >= FSCACHE_OBJECT_DYING) {
ret = -ENOBUFS;
spin_unlock(&cookie->parent->lock);
goto cant_attach_object;
}
object->parent = p;
spin_lock(&p->lock);
p->n_children++;
spin_unlock(&p->lock);
break;
}
}
spin_unlock(&cookie->parent->lock);
/* attach to the cache's object list */
if (list_empty(&object->cache_link)) {
spin_lock(&cache->object_list_lock);
list_add(&object->cache_link, &cache->object_list);
spin_unlock(&cache->object_list_lock);
}
/* attach to the cookie */
object->cookie = cookie;
atomic_inc(&cookie->usage);
hlist_add_head(&object->cookie_link, &cookie->backing_objects);
fscache_objlist_add(object);
ret = 0;
cant_attach_object:
spin_unlock(&cookie->lock);
_leave(" = %d", ret);
return ret;
}
/*
* Invalidate an object. Callable with spinlocks held.
*/
void __fscache_invalidate(struct fscache_cookie *cookie)
{
struct fscache_object *object;
_enter("{%s}", cookie->def->name);
fscache_stat(&fscache_n_invalidates);
/* Only permit invalidation of data files. Invalidating an index will
* require the caller to release all its attachments to the tree rooted
* there, and if it's doing that, it may as well just retire the
* cookie.
*/
ASSERTCMP(cookie->def->type, ==, FSCACHE_COOKIE_TYPE_DATAFILE);
/* We will be updating the cookie too. */
BUG_ON(!cookie->def->get_aux);
/* If there's an object, we tell the object state machine to handle the
* invalidation on our behalf, otherwise there's nothing to do.
*/
if (!hlist_empty(&cookie->backing_objects)) {
spin_lock(&cookie->lock);
if (!hlist_empty(&cookie->backing_objects) &&
!test_and_set_bit(FSCACHE_COOKIE_INVALIDATING,
&cookie->flags)) {
object = hlist_entry(cookie->backing_objects.first,
struct fscache_object,
cookie_link);
if (object->state < FSCACHE_OBJECT_DYING)
fscache_raise_event(
object, FSCACHE_OBJECT_EV_INVALIDATE);
}
spin_unlock(&cookie->lock);
}
_leave("");
}
EXPORT_SYMBOL(__fscache_invalidate);
/*
* Wait for object invalidation to complete.
*/
void __fscache_wait_on_invalidate(struct fscache_cookie *cookie)
{
_enter("%p", cookie);
wait_on_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING,
fscache_wait_bit_interruptible,
TASK_UNINTERRUPTIBLE);
_leave("");
}
EXPORT_SYMBOL(__fscache_wait_on_invalidate);
/*
* update the index entries backing a cookie
*/
void __fscache_update_cookie(struct fscache_cookie *cookie)
{
struct fscache_object *object;
struct hlist_node *_p;
fscache_stat(&fscache_n_updates);
if (!cookie) {
fscache_stat(&fscache_n_updates_null);
_leave(" [no cookie]");
return;
}
_enter("{%s}", cookie->def->name);
BUG_ON(!cookie->def->get_aux);
spin_lock(&cookie->lock);
/* update the index entry on disk in each cache backing this cookie */
hlist_for_each_entry(object, _p,
&cookie->backing_objects, cookie_link) {
fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
}
spin_unlock(&cookie->lock);
_leave("");
}
EXPORT_SYMBOL(__fscache_update_cookie);
/*
* release a cookie back to the cache
* - the object will be marked as recyclable on disk if retire is true
* - all dependents of this cookie must have already been unregistered
* (indices/files/pages)
*/
void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
{
struct fscache_cache *cache;
struct fscache_object *object;
unsigned long event;
fscache_stat(&fscache_n_relinquishes);
if (retire)
fscache_stat(&fscache_n_relinquishes_retire);
if (!cookie) {
fscache_stat(&fscache_n_relinquishes_null);
_leave(" [no cookie]");
return;
}
_enter("%p{%s,%p},%d",
cookie, cookie->def->name, cookie->netfs_data, retire);
if (atomic_read(&cookie->n_children) != 0) {
printk(KERN_ERR "FS-Cache: Cookie '%s' still has children\n",
cookie->def->name);
BUG();
}
/* wait for the cookie to finish being instantiated (or to fail) */
if (test_bit(FSCACHE_COOKIE_CREATING, &cookie->flags)) {
fscache_stat(&fscache_n_relinquishes_waitcrt);
wait_on_bit(&cookie->flags, FSCACHE_COOKIE_CREATING,
fscache_wait_bit, TASK_UNINTERRUPTIBLE);
}
event = retire ? FSCACHE_OBJECT_EV_RETIRE : FSCACHE_OBJECT_EV_RELEASE;
try_again:
spin_lock(&cookie->lock);
/* break links with all the active objects */
while (!hlist_empty(&cookie->backing_objects)) {
int n_reads;
object = hlist_entry(cookie->backing_objects.first,
struct fscache_object,
cookie_link);
_debug("RELEASE OBJ%x", object->debug_id);
set_bit(FSCACHE_COOKIE_WAITING_ON_READS, &cookie->flags);
n_reads = atomic_read(&object->n_reads);
if (n_reads) {
int n_ops = object->n_ops;
int n_in_progress = object->n_in_progress;
spin_unlock(&cookie->lock);
printk(KERN_ERR "FS-Cache:"
" Cookie '%s' still has %d outstanding reads (%d,%d)\n",
cookie->def->name,
n_reads, n_ops, n_in_progress);
wait_on_bit(&cookie->flags, FSCACHE_COOKIE_WAITING_ON_READS,
fscache_wait_bit, TASK_UNINTERRUPTIBLE);
printk("Wait finished\n");
goto try_again;
}
/* detach each cache object from the object cookie */
spin_lock(&object->lock);
hlist_del_init(&object->cookie_link);
cache = object->cache;
object->cookie = NULL;
fscache_raise_event(object, event);
spin_unlock(&object->lock);
if (atomic_dec_and_test(&cookie->usage))
/* the cookie refcount shouldn't be reduced to 0 yet */
BUG();
}
/* detach pointers back to the netfs */
cookie->netfs_data = NULL;
cookie->def = NULL;
spin_unlock(&cookie->lock);
if (cookie->parent) {
ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0);
ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0);
atomic_dec(&cookie->parent->n_children);
}
/* finally dispose of the cookie */
ASSERTCMP(atomic_read(&cookie->usage), >, 0);
fscache_cookie_put(cookie);
_leave("");
}
EXPORT_SYMBOL(__fscache_relinquish_cookie);
/*
* destroy a cookie
*/
void __fscache_cookie_put(struct fscache_cookie *cookie)
{
struct fscache_cookie *parent;
_enter("%p", cookie);
for (;;) {
_debug("FREE COOKIE %p", cookie);
parent = cookie->parent;
BUG_ON(!hlist_empty(&cookie->backing_objects));
kmem_cache_free(fscache_cookie_jar, cookie);
if (!parent)
break;
cookie = parent;
BUG_ON(atomic_read(&cookie->usage) <= 0);
if (!atomic_dec_and_test(&cookie->usage))
break;
}
_leave("");
}