fs/squashfs/cache.c

8  * cache.c
15  * This file implements a generic cache implementation used for both caches,
16  * plus functions layered ontop of the generic cache implementation to
19  * To avoid out of memory and fragmentation issues with vmalloc the cache
22  * It should be noted that the cache is not used for file datablocks, these
23  * are decompressed and cached in the page-cache in the normal way.  The
24  * cache is only used to temporarily cache fragment and metadata blocks
49  * Look-up block in cache, and increment usage count.  If not in cache, read
53 	struct squashfs_cache *cache, u64 block, int length)
58 	spin_lock(&cache->lock);
61 		for (i = cache->curr_blk, n = 0; n < cache->entries; n++) {
62 			if (cache->entry[i].block == block) {
63 				cache->curr_blk = i;
66 			i = (i + 1) % cache->entries;
69 		if (n == cache->entries) {
71 			 * Block not in cache, if all cache entries are used
74 			if (cache->unused == 0) {
75 				cache->num_waiters++;
76 				spin_unlock(&cache->lock);
77 				wait_event(cache->wait_queue, cache->unused);
78 				spin_lock(&cache->lock);
79 				cache->num_waiters--;
84 			 * At least one unused cache entry.  A simple
86 			 * be evicted from the cache.
88 			i = cache->next_blk;
89 			for (n = 0; n < cache->entries; n++) {
90 				if (cache->entry[i].refcount == 0)
92 				i = (i + 1) % cache->entries;
95 			cache->next_blk = (i + 1) % cache->entries;
96 			entry = &cache->entry[i];
99 			 * Initialise chosen cache entry, and fill it in from
102 			cache->unused--;
108 			spin_unlock(&cache->lock);
113 			spin_lock(&cache->lock);
122 			 * have looked it up in the cache, and have slept
126 				spin_unlock(&cache->lock);
129 				spin_unlock(&cache->lock);
135 		 * Block already in cache.  Increment refcount so it doesn't
137 		 * previously unused there's one less cache entry available
140 		entry = &cache->entry[i];
142 			cache->unused--;
151 			spin_unlock(&cache->lock);
154 			spin_unlock(&cache->lock);
161 		cache->name, i, entry->block, entry->refcount, entry->error);
164 		ERROR("Unable to read %s cache entry [%llx]\n", cache->name,
171  * Release cache entry, once usage count is zero it can be reused.
175 	struct squashfs_cache *cache = entry->cache;
177 	spin_lock(&cache->lock);
180 		cache->unused++;
185 		if (cache->num_waiters) {
186 			spin_unlock(&cache->lock);
187 			wake_up(&cache->wait_queue);
191 	spin_unlock(&cache->lock);
195  * Delete cache reclaiming all kmalloced buffers.
197 void squashfs_cache_delete(struct squashfs_cache *cache)
201 	if (cache == NULL)
204 	for (i = 0; i < cache->entries; i++) {
205 		if (cache->entry[i].data) {
206 			for (j = 0; j < cache->pages; j++)
207 				kfree(cache->entry[i].data[j]);
208 			kfree(cache->entry[i].data);
210 		kfree(cache->entry[i].actor);
213 	kfree(cache->entry);
214 	kfree(cache);
219  * Initialise cache allocating the specified number of entries, each of
227 	struct squashfs_cache *cache = kzalloc(sizeof(*cache), GFP_KERNEL);
229 	if (cache == NULL) {
230 		ERROR("Failed to allocate %s cache\n", name);
234 	cache->entry = kcalloc(entries, sizeof(*(cache->entry)), GFP_KERNEL);
235 	if (cache->entry == NULL) {
236 		ERROR("Failed to allocate %s cache\n", name);
240 	cache->curr_blk = 0;
241 	cache->next_blk = 0;
242 	cache->unused = entries;
243 	cache->entries = entries;
244 	cache->block_size = block_size;
245 	cache->pages = block_size >> PAGE_SHIFT;
246 	cache->pages = cache->pages ? cache->pages : 1;
247 	cache->name = name;
248 	cache->num_waiters = 0;
249 	spin_lock_init(&cache->lock);
250 	init_waitqueue_head(&cache->wait_queue);
253 		struct squashfs_cache_entry *entry = &cache->entry[i];
255 		init_waitqueue_head(&cache->entry[i].wait_queue);
256 		entry->cache = cache;
258 		entry->data = kcalloc(cache->pages, sizeof(void *), GFP_KERNEL);
260 			ERROR("Failed to allocate %s cache entry\n", name);
264 		for (j = 0; j < cache->pages; j++) {
273 						cache->pages, 0);
275 			ERROR("Failed to allocate %s cache entry\n", name);
280 	return cache;
283 	squashfs_cache_delete(cache);
289  * Copy up to length bytes from cache entry to buffer starting at offset bytes
290  * into the cache entry.  If there's not length bytes then copy the number of
376  * Look-up in the fragmment cache the fragment located at <start_block> in the
391  * filesystem.  The cache is used here to avoid duplicating locking and