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|
/* 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);
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;
INIT_RADIX_TREE(&cookie->stores, GFP_NOFS);
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
|