diff options
| -rw-r--r-- | fs/fscache/Makefile | 1 | ||||
| -rw-r--r-- | fs/fscache/cache.c | 166 | ||||
| -rw-r--r-- | fs/fscache/internal.h | 20 | ||||
| -rw-r--r-- | include/linux/fscache.h | 9 |
4 files changed, 195 insertions, 1 deletions
diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile index bc1f3b9d811..556708bb979 100644 --- a/fs/fscache/Makefile +++ b/fs/fscache/Makefile @@ -3,6 +3,7 @@ # fscache-y := \ + cache.o \ fsdef.o \ main.o diff --git a/fs/fscache/cache.c b/fs/fscache/cache.c new file mode 100644 index 00000000000..1a28df36dd9 --- /dev/null +++ b/fs/fscache/cache.c @@ -0,0 +1,166 @@ +/* FS-Cache cache handling + * + * 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. + */ + +#define FSCACHE_DEBUG_LEVEL CACHE +#include <linux/module.h> +#include <linux/slab.h> +#include "internal.h" + +LIST_HEAD(fscache_cache_list); +DECLARE_RWSEM(fscache_addremove_sem); + +static LIST_HEAD(fscache_cache_tag_list); + +/* + * look up a cache tag + */ +struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *name) +{ + struct fscache_cache_tag *tag, *xtag; + + /* firstly check for the existence of the tag under read lock */ + down_read(&fscache_addremove_sem); + + list_for_each_entry(tag, &fscache_cache_tag_list, link) { + if (strcmp(tag->name, name) == 0) { + atomic_inc(&tag->usage); + up_read(&fscache_addremove_sem); + return tag; + } + } + + up_read(&fscache_addremove_sem); + + /* the tag does not exist - create a candidate */ + xtag = kzalloc(sizeof(*xtag) + strlen(name) + 1, GFP_KERNEL); + if (!xtag) + /* return a dummy tag if out of memory */ + return ERR_PTR(-ENOMEM); + + atomic_set(&xtag->usage, 1); + strcpy(xtag->name, name); + + /* write lock, search again and add if still not present */ + down_write(&fscache_addremove_sem); + + list_for_each_entry(tag, &fscache_cache_tag_list, link) { + if (strcmp(tag->name, name) == 0) { + atomic_inc(&tag->usage); + up_write(&fscache_addremove_sem); + kfree(xtag); + return tag; + } + } + + list_add_tail(&xtag->link, &fscache_cache_tag_list); + up_write(&fscache_addremove_sem); + return xtag; +} + +/* + * release a reference to a cache tag + */ +void __fscache_release_cache_tag(struct fscache_cache_tag *tag) +{ + if (tag != ERR_PTR(-ENOMEM)) { + down_write(&fscache_addremove_sem); + + if (atomic_dec_and_test(&tag->usage)) + list_del_init(&tag->link); + else + tag = NULL; + + up_write(&fscache_addremove_sem); + + kfree(tag); + } +} + +/* + * select a cache in which to store an object + * - the cache addremove semaphore must be at least read-locked by the caller + * - the object will never be an index + */ +struct fscache_cache *fscache_select_cache_for_object( + struct fscache_cookie *cookie) +{ + struct fscache_cache_tag *tag; + struct fscache_object *object; + struct fscache_cache *cache; + + _enter(""); + + if (list_empty(&fscache_cache_list)) { + _leave(" = NULL [no cache]"); + return NULL; + } + + /* we check the parent to determine the cache to use */ + spin_lock(&cookie->lock); + + /* the first in the parent's backing list should be the preferred + * cache */ + if (!hlist_empty(&cookie->backing_objects)) { + object = hlist_entry(cookie->backing_objects.first, + struct fscache_object, cookie_link); + + cache = object->cache; + if (object->state >= FSCACHE_OBJECT_DYING || + test_bit(FSCACHE_IOERROR, &cache->flags)) + cache = NULL; + + spin_unlock(&cookie->lock); + _leave(" = %p [parent]", cache); + return cache; + } + + /* the parent is unbacked */ + if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) { + /* cookie not an index and is unbacked */ + spin_unlock(&cookie->lock); + _leave(" = NULL [cookie ub,ni]"); + return NULL; + } + + spin_unlock(&cookie->lock); + + if (!cookie->def->select_cache) + goto no_preference; + + /* ask the netfs for its preference */ + tag = cookie->def->select_cache(cookie->parent->netfs_data, + cookie->netfs_data); + if (!tag) + goto no_preference; + + if (tag == ERR_PTR(-ENOMEM)) { + _leave(" = NULL [nomem tag]"); + return NULL; + } + + if (!tag->cache) { + _leave(" = NULL [unbacked tag]"); + return NULL; + } + + if (test_bit(FSCACHE_IOERROR, &tag->cache->flags)) + return NULL; + + _leave(" = %p [specific]", tag->cache); + return tag->cache; + +no_preference: + /* netfs has no preference - just select first cache */ + cache = list_entry(fscache_cache_list.next, + struct fscache_cache, link); + _leave(" = %p [first]", cache); + return cache; +} diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h index 4113af8d166..0a2069afa41 100644 --- a/fs/fscache/internal.h +++ b/fs/fscache/internal.h @@ -28,6 +28,15 @@ #define FSCACHE_MAX_THREADS 32 /* + * fsc-cache.c + */ +extern struct list_head fscache_cache_list; +extern struct rw_semaphore fscache_addremove_sem; + +extern struct fscache_cache *fscache_select_cache_for_object( + struct fscache_cookie *); + +/* * fsc-fsdef.c */ extern struct fscache_cookie fscache_fsdef_index; @@ -168,6 +177,17 @@ extern const struct file_operations fscache_stats_fops; #define fscache_stat(stat) do {} while (0) #endif +/* + * raise an event on an object + * - if the event is not masked for that object, then the object is + * queued for attention by the thread pool. + */ +static inline void fscache_raise_event(struct fscache_object *object, + unsigned event) +{ + BUG(); // TODO +} + /*****************************************************************************/ /* * debug tracing diff --git a/include/linux/fscache.h b/include/linux/fscache.h index feb3b0e0af4..9584c094d69 100644 --- a/include/linux/fscache.h +++ b/include/linux/fscache.h @@ -173,6 +173,8 @@ struct fscache_netfs { * - these are undefined symbols when FS-Cache is not configured and the * optimiser takes care of not using them */ +extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *); +extern void __fscache_release_cache_tag(struct fscache_cache_tag *); /** * fscache_register_netfs - Register a filesystem as desiring caching services @@ -218,7 +220,10 @@ void fscache_unregister_netfs(struct fscache_netfs *netfs) static inline struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name) { - return NULL; + if (fscache_available()) + return __fscache_lookup_cache_tag(name); + else + return NULL; } /** @@ -233,6 +238,8 @@ struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name) static inline void fscache_release_cache_tag(struct fscache_cache_tag *tag) { + if (fscache_available()) + __fscache_release_cache_tag(tag); } /** |