2  * Squashfs - a compressed read only filesystem for Linux
19  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
21  * cache.c
28  * This file implements a generic cache implementation used for both caches,
29  * plus functions layered ontop of the generic cache implementation to
32  * To avoid out of memory and fragmentation isssues with vmalloc the cache
35  * It should be noted that the cache is not used for file datablocks, these
36  * are decompressed and cached in the page-cache in the normal way.  The
37  * cache is only used to temporarily cache fragment and metadata blocks
42  * have been packed with it, these because of locality-of-reference may be read
63  * Look-up block in cache, and increment usage count.  If not in cache, read
67 	struct squashfs_cache *cache, u64 block, int length)  in squashfs_cache_get()  argument
70 	struct squashfs_cache_entry *entry;  in squashfs_cache_get()  local
72 	spin_lock(&cache->lock);  in squashfs_cache_get()
75 		for (i = 0; i < cache->entries; i++)  in squashfs_cache_get()
76 			if (cache->entry[i].block == block)  in squashfs_cache_get()
79 		if (i == cache->entries) {  in squashfs_cache_get()
81 			 * Block not in cache, if all cache entries are used  in squashfs_cache_get()
84 			if (cache->unused == 0) {  in squashfs_cache_get()
85 				cache->num_waiters++;  in squashfs_cache_get()
86 				spin_unlock(&cache->lock);  in squashfs_cache_get()
87 				wait_event(cache->wait_queue, cache->unused);  in squashfs_cache_get()
88 				spin_lock(&cache->lock);  in squashfs_cache_get()
89 				cache->num_waiters--;  in squashfs_cache_get()
94 			 * At least one unused cache entry.  A simple  in squashfs_cache_get()
95 			 * round-robin strategy is used to choose the entry to  in squashfs_cache_get()
96 			 * be evicted from the cache.  in squashfs_cache_get()
98 			i = cache->next_blk;  in squashfs_cache_get()
99 			for (n = 0; n < cache->entries; n++) {  in squashfs_cache_get()
100 				if (cache->entry[i].refcount == 0)  in squashfs_cache_get()
102 				i = (i + 1) % cache->entries;  in squashfs_cache_get()
105 			cache->next_blk = (i + 1) % cache->entries;  in squashfs_cache_get()
106 			entry = &cache->entry[i];  in squashfs_cache_get()
109 			 * Initialise choosen cache entry, and fill it in from  in squashfs_cache_get()
112 			cache->unused--;  in squashfs_cache_get()
113 			entry->block = block;  in squashfs_cache_get()
114 			entry->refcount = 1;  in squashfs_cache_get()
115 			entry->pending = 1;  in squashfs_cache_get()
116 			entry->num_waiters = 0;  in squashfs_cache_get()
117 			entry->error = 0;  in squashfs_cache_get()
118 			spin_unlock(&cache->lock);  in squashfs_cache_get()
120 			entry->length = squashfs_read_data(sb, entry->data,  in squashfs_cache_get()
121 				block, length, &entry->next_index,  in squashfs_cache_get()
122 				cache->block_size);  in squashfs_cache_get()
124 			spin_lock(&cache->lock);  in squashfs_cache_get()
126 			if (entry->length < 0)  in squashfs_cache_get()
127 				entry->error = entry->length;  in squashfs_cache_get()
129 			entry->pending = 0;  in squashfs_cache_get()
132 			 * While filling this entry one or more other processes  in squashfs_cache_get()
133 			 * have looked it up in the cache, and have slept  in squashfs_cache_get()
136 			if (entry->num_waiters) {  in squashfs_cache_get()
137 				spin_unlock(&cache->lock);  in squashfs_cache_get()
138 				wake_up_all(&entry->wait_queue);  in squashfs_cache_get()
140 				spin_unlock(&cache->lock);  in squashfs_cache_get()
146 		 * Block already in cache.  Increment refcount so it doesn't  in squashfs_cache_get()
148 		 * previously unused there's one less cache entry available  in squashfs_cache_get()
151 		entry = &cache->entry[i];  in squashfs_cache_get()
152 		if (entry->refcount == 0)  in squashfs_cache_get()
153 			cache->unused--;  in squashfs_cache_get()
154 		entry->refcount++;  in squashfs_cache_get()
157 		 * If the entry is currently being filled in by another process  in squashfs_cache_get()
160 		if (entry->pending) {  in squashfs_cache_get()
161 			entry->num_waiters++;  in squashfs_cache_get()
162 			spin_unlock(&cache->lock);  in squashfs_cache_get()
163 			wait_event(entry->wait_queue, !entry->pending);  in squashfs_cache_get()
165 			spin_unlock(&cache->lock);  in squashfs_cache_get()
172 		cache->name, i, entry->block, entry->refcount, entry->error);  in squashfs_cache_get()
174 	if (entry->error)  in squashfs_cache_get()
175 		ERROR("Unable to read %s cache entry [%llx]\n", cache->name,  in squashfs_cache_get()
177 	return entry;  in squashfs_cache_get()
182  * Release cache entry, once usage count is zero it can be reused.
184 void squashfs_cache_put(struct squashfs_cache_entry *entry)  in squashfs_cache_put()  argument
186 	struct squashfs_cache *cache = entry->cache;  in squashfs_cache_put()  local
188 	spin_lock(&cache->lock);  in squashfs_cache_put()
189 	entry->refcount--;  in squashfs_cache_put()
190 	if (entry->refcount == 0) {  in squashfs_cache_put()
191 		cache->unused++;  in squashfs_cache_put()
196 		if (cache->num_waiters) {  in squashfs_cache_put()
197 			spin_unlock(&cache->lock);  in squashfs_cache_put()
198 			wake_up(&cache->wait_queue);  in squashfs_cache_put()
202 	spin_unlock(&cache->lock);  in squashfs_cache_put()
206  * Delete cache reclaiming all kmalloced buffers.
208 void squashfs_cache_delete(struct squashfs_cache *cache)  in squashfs_cache_delete()  argument
212 	if (cache == NULL)  in squashfs_cache_delete()
215 	for (i = 0; i < cache->entries; i++) {  in squashfs_cache_delete()
216 		if (cache->entry[i].data) {  in squashfs_cache_delete()
217 			for (j = 0; j < cache->pages; j++)  in squashfs_cache_delete()
218 				kfree(cache->entry[i].data[j]);  in squashfs_cache_delete()
219 			kfree(cache->entry[i].data);  in squashfs_cache_delete()
223 	kfree(cache->entry);  in squashfs_cache_delete()
224 	kfree(cache);  in squashfs_cache_delete()
229  * Initialise cache allocating the specified number of entries, each of
230  * size block_size.  To avoid vmalloc fragmentation issues each entry
237 	struct squashfs_cache *cache = kzalloc(sizeof(*cache), GFP_KERNEL);  in squashfs_cache_init()  local
239 	if (cache == NULL) {  in squashfs_cache_init()
240 		ERROR("Failed to allocate %s cache\n", name);  in squashfs_cache_init()
244 	cache->entry = kcalloc(entries, sizeof(*(cache->entry)), GFP_KERNEL);  in squashfs_cache_init()
245 	if (cache->entry == NULL) {  in squashfs_cache_init()
246 		ERROR("Failed to allocate %s cache\n", name);  in squashfs_cache_init()
250 	cache->next_blk = 0;  in squashfs_cache_init()
251 	cache->unused = entries;  in squashfs_cache_init()
252 	cache->entries = entries;  in squashfs_cache_init()
253 	cache->block_size = block_size;  in squashfs_cache_init()
254 	cache->pages = block_size >> PAGE_CACHE_SHIFT;  in squashfs_cache_init()
255 	cache->name = name;  in squashfs_cache_init()
256 	cache->num_waiters = 0;  in squashfs_cache_init()
257 	spin_lock_init(&cache->lock);  in squashfs_cache_init()
258 	init_waitqueue_head(&cache->wait_queue);  in squashfs_cache_init()
261 		struct squashfs_cache_entry *entry = &cache->entry[i];  in squashfs_cache_init()  local
263 		init_waitqueue_head(&cache->entry[i].wait_queue);  in squashfs_cache_init()
264 		entry->cache = cache;  in squashfs_cache_init()
265 		entry->block = SQUASHFS_INVALID_BLK;  in squashfs_cache_init()
266 		entry->data = kcalloc(cache->pages, sizeof(void *), GFP_KERNEL);  in squashfs_cache_init()
267 		if (entry->data == NULL) {  in squashfs_cache_init()
268 			ERROR("Failed to allocate %s cache entry\n", name);  in squashfs_cache_init()
272 		for (j = 0; j < cache->pages; j++) {  in squashfs_cache_init()
273 			entry->data[j] = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);  in squashfs_cache_init()
274 			if (entry->data[j] == NULL) {  in squashfs_cache_init()
281 	return cache;  in squashfs_cache_init()
284 	squashfs_cache_delete(cache);  in squashfs_cache_init()
290  * Copy upto length bytes from cache entry to buffer starting at offset bytes
291  * into the cache entry.  If there's not length bytes then copy the number of
294 int squashfs_copy_data(void *buffer, struct squashfs_cache_entry *entry,  in squashfs_copy_data()  argument
302 		return min(length, entry->length - offset);  in squashfs_copy_data()
304 	while (offset < entry->length) {  in squashfs_copy_data()
305 		void *buff = entry->data[offset / PAGE_CACHE_SIZE]  in squashfs_copy_data()
307 		int bytes = min_t(int, entry->length - offset,  in squashfs_copy_data()
308 				PAGE_CACHE_SIZE - (offset % PAGE_CACHE_SIZE));  in squashfs_copy_data()
318 		remaining -= bytes;  in squashfs_copy_data()
322 	return length - remaining;  in squashfs_copy_data()
335 	struct squashfs_sb_info *msblk = sb->s_fs_info;  in squashfs_read_metadata()
337 	struct squashfs_cache_entry *entry;  in squashfs_read_metadata()  local
342 		entry = squashfs_cache_get(sb, msblk->block_cache, *block, 0);  in squashfs_read_metadata()
343 		if (entry->error)  in squashfs_read_metadata()
344 			return entry->error;  in squashfs_read_metadata()
345 		else if (*offset >= entry->length)  in squashfs_read_metadata()
346 			return -EIO;  in squashfs_read_metadata()
348 		bytes = squashfs_copy_data(buffer, entry, *offset, length);  in squashfs_read_metadata()
351 		length -= bytes;  in squashfs_read_metadata()
354 		if (*offset == entry->length) {  in squashfs_read_metadata()
355 			*block = entry->next_index;  in squashfs_read_metadata()
359 		squashfs_cache_put(entry);  in squashfs_read_metadata()
367  * Look-up in the fragmment cache the fragment located at <start_block> in the
373 	struct squashfs_sb_info *msblk = sb->s_fs_info;  in squashfs_get_fragment()
375 	return squashfs_cache_get(sb, msblk->fragment_cache, start_block,  in squashfs_get_fragment()
382  * filesystem.  The cache is used here to avoid duplicating locking and
388 	struct squashfs_sb_info *msblk = sb->s_fs_info;  in squashfs_get_datablock()
390 	return squashfs_cache_get(sb, msblk->read_page, start_block, length);  in squashfs_get_datablock()
400 	int pages = (length + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;  in squashfs_read_table()
404 		return -ENOMEM;  in squashfs_read_table()