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