1 // SPDX-License-Identifier: GPL-2.0-or-later
3  * Squashfs - a compressed read only filesystem for Linux
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
25  * which have been read as as a result of a metadata (i.e. inode or
29  * have been packed with it, these because of locality-of-reference may be read
49  * Look-up block in cache, and increment usage count.  If not in cache, read
53 	struct squashfs_cache *cache, u64 block, int length)  in squashfs_cache_get()  argument
55 	int i, n;  in squashfs_cache_get()  local
58 	spin_lock(&cache->lock);  in squashfs_cache_get()
61 		for (i = cache->curr_blk, n = 0; n < cache->entries; n++) {  in squashfs_cache_get()
62 			if (cache->entry[i].block == block) {  in squashfs_cache_get()
63 				cache->curr_blk = i;  in squashfs_cache_get()
66 			i = (i + 1) % cache->entries;  in squashfs_cache_get()
69 		if (n == cache->entries) {  in squashfs_cache_get()
71 			 * Block not in cache, if all cache entries are used  in squashfs_cache_get()
74 			if (cache->unused == 0) {  in squashfs_cache_get()
75 				cache->num_waiters++;  in squashfs_cache_get()
76 				spin_unlock(&cache->lock);  in squashfs_cache_get()
77 				wait_event(cache->wait_queue, cache->unused);  in squashfs_cache_get()
78 				spin_lock(&cache->lock);  in squashfs_cache_get()
79 				cache->num_waiters--;  in squashfs_cache_get()
84 			 * At least one unused cache entry.  A simple  in squashfs_cache_get()
85 			 * round-robin strategy is used to choose the entry to  in squashfs_cache_get()
86 			 * be evicted from the cache.  in squashfs_cache_get()
88 			i = cache->next_blk;  in squashfs_cache_get()
89 			for (n = 0; n < cache->entries; n++) {  in squashfs_cache_get()
90 				if (cache->entry[i].refcount == 0)  in squashfs_cache_get()
92 				i = (i + 1) % cache->entries;  in squashfs_cache_get()
95 			cache->next_blk = (i + 1) % cache->entries;  in squashfs_cache_get()
96 			entry = &cache->entry[i];  in squashfs_cache_get()
99 			 * Initialise chosen cache entry, and fill it in from  in squashfs_cache_get()
102 			cache->unused--;  in squashfs_cache_get()
103 			entry->block = block;  in squashfs_cache_get()
104 			entry->refcount = 1;  in squashfs_cache_get()
105 			entry->pending = 1;  in squashfs_cache_get()
106 			entry->num_waiters = 0;  in squashfs_cache_get()
107 			entry->error = 0;  in squashfs_cache_get()
108 			spin_unlock(&cache->lock);  in squashfs_cache_get()
110 			entry->length = squashfs_read_data(sb, block, length,  in squashfs_cache_get()
111 				&entry->next_index, entry->actor);  in squashfs_cache_get()
113 			spin_lock(&cache->lock);  in squashfs_cache_get()
115 			if (entry->length < 0)  in squashfs_cache_get()
116 				entry->error = entry->length;  in squashfs_cache_get()
118 			entry->pending = 0;  in squashfs_cache_get()
122 			 * have looked it up in the cache, and have slept  in squashfs_cache_get()
125 			if (entry->num_waiters) {  in squashfs_cache_get()
126 				spin_unlock(&cache->lock);  in squashfs_cache_get()
127 				wake_up_all(&entry->wait_queue);  in squashfs_cache_get()
129 				spin_unlock(&cache->lock);  in squashfs_cache_get()
135 		 * Block already in cache.  Increment refcount so it doesn't  in squashfs_cache_get()
137 		 * previously unused there's one less cache entry available  in squashfs_cache_get()
140 		entry = &cache->entry[i];  in squashfs_cache_get()
141 		if (entry->refcount == 0)  in squashfs_cache_get()
142 			cache->unused--;  in squashfs_cache_get()
143 		entry->refcount++;  in squashfs_cache_get()
149 		if (entry->pending) {  in squashfs_cache_get()
150 			entry->num_waiters++;  in squashfs_cache_get()
151 			spin_unlock(&cache->lock);  in squashfs_cache_get()
152 			wait_event(entry->wait_queue, !entry->pending);  in squashfs_cache_get()
154 			spin_unlock(&cache->lock);  in squashfs_cache_get()
160 	TRACE("Got %s %d, start block %lld, refcount %d, error %d\n",  in squashfs_cache_get()
161 		cache->name, i, entry->block, entry->refcount, entry->error);  in squashfs_cache_get()
163 	if (entry->error)  in squashfs_cache_get()
164 		ERROR("Unable to read %s cache entry [%llx]\n", cache->name,  in squashfs_cache_get()
165 							block);  in squashfs_cache_get()
171  * Release cache entry, once usage count is zero it can be reused.
175 	struct squashfs_cache *cache = entry->cache;  in squashfs_cache_put()  local
177 	spin_lock(&cache->lock);  in squashfs_cache_put()
178 	entry->refcount--;  in squashfs_cache_put()
179 	if (entry->refcount == 0) {  in squashfs_cache_put()
180 		cache->unused++;  in squashfs_cache_put()
182 		 * If there's any processes waiting for a block to become  in squashfs_cache_put()
185 		if (cache->num_waiters) {  in squashfs_cache_put()
186 			spin_unlock(&cache->lock);  in squashfs_cache_put()
187 			wake_up(&cache->wait_queue);  in squashfs_cache_put()
191 	spin_unlock(&cache->lock);  in squashfs_cache_put()
195  * Delete cache reclaiming all kmalloced buffers.
197 void squashfs_cache_delete(struct squashfs_cache *cache)  in squashfs_cache_delete()  argument
199 	int i, j;  in squashfs_cache_delete()  local
201 	if (cache == NULL)  in squashfs_cache_delete()
204 	for (i = 0; i < cache->entries; i++) {  in squashfs_cache_delete()
205 		if (cache->entry[i].data) {  in squashfs_cache_delete()
206 			for (j = 0; j < cache->pages; j++)  in squashfs_cache_delete()
207 				kfree(cache->entry[i].data[j]);  in squashfs_cache_delete()
208 			kfree(cache->entry[i].data);  in squashfs_cache_delete()
210 		kfree(cache->entry[i].actor);  in squashfs_cache_delete()
213 	kfree(cache->entry);  in squashfs_cache_delete()
214 	kfree(cache);  in squashfs_cache_delete()
219  * Initialise cache allocating the specified number of entries, each of
220  * size block_size.  To avoid vmalloc fragmentation issues each entry
226 	int i, j;  in squashfs_cache_init()  local
227 	struct squashfs_cache *cache = kzalloc(sizeof(*cache), GFP_KERNEL);  in squashfs_cache_init()  local
229 	if (cache == NULL) {  in squashfs_cache_init()
230 		ERROR("Failed to allocate %s cache\n", name);  in squashfs_cache_init()
234 	cache->entry = kcalloc(entries, sizeof(*(cache->entry)), GFP_KERNEL);  in squashfs_cache_init()
235 	if (cache->entry == NULL) {  in squashfs_cache_init()
236 		ERROR("Failed to allocate %s cache\n", name);  in squashfs_cache_init()
240 	cache->curr_blk = 0;  in squashfs_cache_init()
241 	cache->next_blk = 0;  in squashfs_cache_init()
242 	cache->unused = entries;  in squashfs_cache_init()
243 	cache->entries = entries;  in squashfs_cache_init()
244 	cache->block_size = block_size;  in squashfs_cache_init()
245 	cache->pages = block_size >> PAGE_SHIFT;  in squashfs_cache_init()
246 	cache->pages = cache->pages ? cache->pages : 1;  in squashfs_cache_init()
247 	cache->name = name;  in squashfs_cache_init()
248 	cache->num_waiters = 0;  in squashfs_cache_init()
249 	spin_lock_init(&cache->lock);  in squashfs_cache_init()
250 	init_waitqueue_head(&cache->wait_queue);  in squashfs_cache_init()
252 	for (i = 0; i < entries; i++) {  in squashfs_cache_init()
253 		struct squashfs_cache_entry *entry = &cache->entry[i];  in squashfs_cache_init()
255 		init_waitqueue_head(&cache->entry[i].wait_queue);  in squashfs_cache_init()
256 		entry->cache = cache;  in squashfs_cache_init()
257 		entry->block = SQUASHFS_INVALID_BLK;  in squashfs_cache_init()
258 		entry->data = kcalloc(cache->pages, sizeof(void *), GFP_KERNEL);  in squashfs_cache_init()
259 		if (entry->data == NULL) {  in squashfs_cache_init()
260 			ERROR("Failed to allocate %s cache entry\n", name);  in squashfs_cache_init()
264 		for (j = 0; j < cache->pages; j++) {  in squashfs_cache_init()
265 			entry->data[j] = kmalloc(PAGE_SIZE, GFP_KERNEL);  in squashfs_cache_init()
266 			if (entry->data[j] == NULL) {  in squashfs_cache_init()
272 		entry->actor = squashfs_page_actor_init(entry->data,  in squashfs_cache_init()
273 						cache->pages, 0);  in squashfs_cache_init()
274 		if (entry->actor == NULL) {  in squashfs_cache_init()
275 			ERROR("Failed to allocate %s cache entry\n", name);  in squashfs_cache_init()
280 	return cache;  in squashfs_cache_init()
283 	squashfs_cache_delete(cache);  in squashfs_cache_init()
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
301 		return min(length, entry->length - offset);  in squashfs_copy_data()
303 	while (offset < entry->length) {  in squashfs_copy_data()
304 		void *buff = entry->data[offset / PAGE_SIZE]  in squashfs_copy_data()
306 		int bytes = min_t(int, entry->length - offset,  in squashfs_copy_data()
307 				PAGE_SIZE - (offset % PAGE_SIZE));  in squashfs_copy_data()
317 		remaining -= bytes;  in squashfs_copy_data()
321 	return length - remaining;  in squashfs_copy_data()
326  * Read length bytes from metadata position <block, offset> (block is the
327  * start of the compressed block on disk, and offset is the offset into
328  * the block once decompressed).  Data is packed into consecutive blocks,
329  * and length bytes may require reading more than one block.
332 		u64 *block, int *offset, int length)  in squashfs_read_metadata()  argument
334 	struct squashfs_sb_info *msblk = sb->s_fs_info;  in squashfs_read_metadata()
338 	TRACE("Entered squashfs_read_metadata [%llx:%x]\n", *block, *offset);  in squashfs_read_metadata()
341 		return -EIO;  in squashfs_read_metadata()
344 		entry = squashfs_cache_get(sb, msblk->block_cache, *block, 0);  in squashfs_read_metadata()
345 		if (entry->error) {  in squashfs_read_metadata()
346 			res = entry->error;  in squashfs_read_metadata()
348 		} else if (*offset >= entry->length) {  in squashfs_read_metadata()
349 			res = -EIO;  in squashfs_read_metadata()
356 		length -= bytes;  in squashfs_read_metadata()
359 		if (*offset == entry->length) {  in squashfs_read_metadata()
360 			*block = entry->next_index;  in squashfs_read_metadata()
376  * Look-up in the fragmment cache the fragment located at <start_block> in the
382 	struct squashfs_sb_info *msblk = sb->s_fs_info;  in squashfs_get_fragment()
384 	return squashfs_cache_get(sb, msblk->fragment_cache, start_block,  in squashfs_get_fragment()
391  * filesystem.  The cache is used here to avoid duplicating locking and
397 	struct squashfs_sb_info *msblk = sb->s_fs_info;  in squashfs_get_datablock()
399 	return squashfs_cache_get(sb, msblk->read_page, start_block, length);  in squashfs_get_datablock()
406 void *squashfs_read_table(struct super_block *sb, u64 block, int length)  in squashfs_read_table()  argument
408 	int pages = (length + PAGE_SIZE - 1) >> PAGE_SHIFT;  in squashfs_read_table()
409 	int i, res;  in squashfs_read_table()  local
415 		return ERR_PTR(-ENOMEM);  in squashfs_read_table()
419 		res = -ENOMEM;  in squashfs_read_table()
425 		res = -ENOMEM;  in squashfs_read_table()
429 	for (i = 0; i < pages; i++, buffer += PAGE_SIZE)  in squashfs_read_table()
430 		data[i] = buffer;  in squashfs_read_table()
432 	res = squashfs_read_data(sb, block, length |  in squashfs_read_table()