1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * zpool memory storage api
4  *
5  * Copyright (C) 2014 Dan Streetman
6  *
7  * This is a common frontend for memory storage pool implementations.
8  * Typically, this is used to store compressed memory.
9  */
10 
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 
13 #include <linux/list.h>
14 #include <linux/types.h>
15 #include <linux/mm.h>
16 #include <linux/slab.h>
17 #include <linux/spinlock.h>
18 #include <linux/module.h>
19 #include <linux/zpool.h>
20 
21 struct zpool {
22 	struct zpool_driver *driver;
23 	void *pool;
24 	const struct zpool_ops *ops;
25 	bool evictable;
26 	bool can_sleep_mapped;
27 
28 	struct list_head list;
29 };
30 
31 static LIST_HEAD(drivers_head);
32 static DEFINE_SPINLOCK(drivers_lock);
33 
34 static LIST_HEAD(pools_head);
35 static DEFINE_SPINLOCK(pools_lock);
36 
37 /**
38  * zpool_register_driver() - register a zpool implementation.
39  * @driver:	driver to register
40  */
zpool_register_driver(struct zpool_driver * driver)41 void zpool_register_driver(struct zpool_driver *driver)
42 {
43 	spin_lock(&drivers_lock);
44 	atomic_set(&driver->refcount, 0);
45 	list_add(&driver->list, &drivers_head);
46 	spin_unlock(&drivers_lock);
47 }
48 EXPORT_SYMBOL(zpool_register_driver);
49 
50 /**
51  * zpool_unregister_driver() - unregister a zpool implementation.
52  * @driver:	driver to unregister.
53  *
54  * Module usage counting is used to prevent using a driver
55  * while/after unloading, so if this is called from module
56  * exit function, this should never fail; if called from
57  * other than the module exit function, and this returns
58  * failure, the driver is in use and must remain available.
59  */
zpool_unregister_driver(struct zpool_driver * driver)60 int zpool_unregister_driver(struct zpool_driver *driver)
61 {
62 	int ret = 0, refcount;
63 
64 	spin_lock(&drivers_lock);
65 	refcount = atomic_read(&driver->refcount);
66 	WARN_ON(refcount < 0);
67 	if (refcount > 0)
68 		ret = -EBUSY;
69 	else
70 		list_del(&driver->list);
71 	spin_unlock(&drivers_lock);
72 
73 	return ret;
74 }
75 EXPORT_SYMBOL(zpool_unregister_driver);
76 
77 /* this assumes @type is null-terminated. */
zpool_get_driver(const char * type)78 static struct zpool_driver *zpool_get_driver(const char *type)
79 {
80 	struct zpool_driver *driver;
81 
82 	spin_lock(&drivers_lock);
83 	list_for_each_entry(driver, &drivers_head, list) {
84 		if (!strcmp(driver->type, type)) {
85 			bool got = try_module_get(driver->owner);
86 
87 			if (got)
88 				atomic_inc(&driver->refcount);
89 			spin_unlock(&drivers_lock);
90 			return got ? driver : NULL;
91 		}
92 	}
93 
94 	spin_unlock(&drivers_lock);
95 	return NULL;
96 }
97 
zpool_put_driver(struct zpool_driver * driver)98 static void zpool_put_driver(struct zpool_driver *driver)
99 {
100 	atomic_dec(&driver->refcount);
101 	module_put(driver->owner);
102 }
103 
104 /**
105  * zpool_has_pool() - Check if the pool driver is available
106  * @type:	The type of the zpool to check (e.g. zbud, zsmalloc)
107  *
108  * This checks if the @type pool driver is available.  This will try to load
109  * the requested module, if needed, but there is no guarantee the module will
110  * still be loaded and available immediately after calling.  If this returns
111  * true, the caller should assume the pool is available, but must be prepared
112  * to handle the @zpool_create_pool() returning failure.  However if this
113  * returns false, the caller should assume the requested pool type is not
114  * available; either the requested pool type module does not exist, or could
115  * not be loaded, and calling @zpool_create_pool() with the pool type will
116  * fail.
117  *
118  * The @type string must be null-terminated.
119  *
120  * Returns: true if @type pool is available, false if not
121  */
zpool_has_pool(char * type)122 bool zpool_has_pool(char *type)
123 {
124 	struct zpool_driver *driver = zpool_get_driver(type);
125 
126 	if (!driver) {
127 		request_module("zpool-%s", type);
128 		driver = zpool_get_driver(type);
129 	}
130 
131 	if (!driver)
132 		return false;
133 
134 	zpool_put_driver(driver);
135 	return true;
136 }
137 EXPORT_SYMBOL(zpool_has_pool);
138 
139 /**
140  * zpool_create_pool() - Create a new zpool
141  * @type:	The type of the zpool to create (e.g. zbud, zsmalloc)
142  * @name:	The name of the zpool (e.g. zram0, zswap)
143  * @gfp:	The GFP flags to use when allocating the pool.
144  * @ops:	The optional ops callback.
145  *
146  * This creates a new zpool of the specified type.  The gfp flags will be
147  * used when allocating memory, if the implementation supports it.  If the
148  * ops param is NULL, then the created zpool will not be evictable.
149  *
150  * Implementations must guarantee this to be thread-safe.
151  *
152  * The @type and @name strings must be null-terminated.
153  *
154  * Returns: New zpool on success, NULL on failure.
155  */
zpool_create_pool(const char * type,const char * name,gfp_t gfp,const struct zpool_ops * ops)156 struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
157 		const struct zpool_ops *ops)
158 {
159 	struct zpool_driver *driver;
160 	struct zpool *zpool;
161 
162 	pr_debug("creating pool type %s\n", type);
163 
164 	driver = zpool_get_driver(type);
165 
166 	if (!driver) {
167 		request_module("zpool-%s", type);
168 		driver = zpool_get_driver(type);
169 	}
170 
171 	if (!driver) {
172 		pr_err("no driver for type %s\n", type);
173 		return NULL;
174 	}
175 
176 	zpool = kmalloc(sizeof(*zpool), gfp);
177 	if (!zpool) {
178 		pr_err("couldn't create zpool - out of memory\n");
179 		zpool_put_driver(driver);
180 		return NULL;
181 	}
182 
183 	zpool->driver = driver;
184 	zpool->pool = driver->create(name, gfp, ops, zpool);
185 	zpool->ops = ops;
186 	zpool->evictable = driver->shrink && ops && ops->evict;
187 	zpool->can_sleep_mapped = driver->sleep_mapped;
188 
189 	if (!zpool->pool) {
190 		pr_err("couldn't create %s pool\n", type);
191 		zpool_put_driver(driver);
192 		kfree(zpool);
193 		return NULL;
194 	}
195 
196 	pr_debug("created pool type %s\n", type);
197 
198 	spin_lock(&pools_lock);
199 	list_add(&zpool->list, &pools_head);
200 	spin_unlock(&pools_lock);
201 
202 	return zpool;
203 }
204 
205 /**
206  * zpool_destroy_pool() - Destroy a zpool
207  * @zpool:	The zpool to destroy.
208  *
209  * Implementations must guarantee this to be thread-safe,
210  * however only when destroying different pools.  The same
211  * pool should only be destroyed once, and should not be used
212  * after it is destroyed.
213  *
214  * This destroys an existing zpool.  The zpool should not be in use.
215  */
zpool_destroy_pool(struct zpool * zpool)216 void zpool_destroy_pool(struct zpool *zpool)
217 {
218 	pr_debug("destroying pool type %s\n", zpool->driver->type);
219 
220 	spin_lock(&pools_lock);
221 	list_del(&zpool->list);
222 	spin_unlock(&pools_lock);
223 	zpool->driver->destroy(zpool->pool);
224 	zpool_put_driver(zpool->driver);
225 	kfree(zpool);
226 }
227 
228 /**
229  * zpool_get_type() - Get the type of the zpool
230  * @zpool:	The zpool to check
231  *
232  * This returns the type of the pool.
233  *
234  * Implementations must guarantee this to be thread-safe.
235  *
236  * Returns: The type of zpool.
237  */
zpool_get_type(struct zpool * zpool)238 const char *zpool_get_type(struct zpool *zpool)
239 {
240 	return zpool->driver->type;
241 }
242 
243 /**
244  * zpool_malloc_support_movable() - Check if the zpool supports
245  *	allocating movable memory
246  * @zpool:	The zpool to check
247  *
248  * This returns if the zpool supports allocating movable memory.
249  *
250  * Implementations must guarantee this to be thread-safe.
251  *
252  * Returns: true if the zpool supports allocating movable memory, false if not
253  */
zpool_malloc_support_movable(struct zpool * zpool)254 bool zpool_malloc_support_movable(struct zpool *zpool)
255 {
256 	return zpool->driver->malloc_support_movable;
257 }
258 
259 /**
260  * zpool_malloc() - Allocate memory
261  * @zpool:	The zpool to allocate from.
262  * @size:	The amount of memory to allocate.
263  * @gfp:	The GFP flags to use when allocating memory.
264  * @handle:	Pointer to the handle to set
265  *
266  * This allocates the requested amount of memory from the pool.
267  * The gfp flags will be used when allocating memory, if the
268  * implementation supports it.  The provided @handle will be
269  * set to the allocated object handle.
270  *
271  * Implementations must guarantee this to be thread-safe.
272  *
273  * Returns: 0 on success, negative value on error.
274  */
zpool_malloc(struct zpool * zpool,size_t size,gfp_t gfp,unsigned long * handle)275 int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
276 			unsigned long *handle)
277 {
278 	return zpool->driver->malloc(zpool->pool, size, gfp, handle);
279 }
280 
281 /**
282  * zpool_free() - Free previously allocated memory
283  * @zpool:	The zpool that allocated the memory.
284  * @handle:	The handle to the memory to free.
285  *
286  * This frees previously allocated memory.  This does not guarantee
287  * that the pool will actually free memory, only that the memory
288  * in the pool will become available for use by the pool.
289  *
290  * Implementations must guarantee this to be thread-safe,
291  * however only when freeing different handles.  The same
292  * handle should only be freed once, and should not be used
293  * after freeing.
294  */
zpool_free(struct zpool * zpool,unsigned long handle)295 void zpool_free(struct zpool *zpool, unsigned long handle)
296 {
297 	zpool->driver->free(zpool->pool, handle);
298 }
299 
300 /**
301  * zpool_shrink() - Shrink the pool size
302  * @zpool:	The zpool to shrink.
303  * @pages:	The number of pages to shrink the pool.
304  * @reclaimed:	The number of pages successfully evicted.
305  *
306  * This attempts to shrink the actual memory size of the pool
307  * by evicting currently used handle(s).  If the pool was
308  * created with no zpool_ops, or the evict call fails for any
309  * of the handles, this will fail.  If non-NULL, the @reclaimed
310  * parameter will be set to the number of pages reclaimed,
311  * which may be more than the number of pages requested.
312  *
313  * Implementations must guarantee this to be thread-safe.
314  *
315  * Returns: 0 on success, negative value on error/failure.
316  */
zpool_shrink(struct zpool * zpool,unsigned int pages,unsigned int * reclaimed)317 int zpool_shrink(struct zpool *zpool, unsigned int pages,
318 			unsigned int *reclaimed)
319 {
320 	return zpool->driver->shrink ?
321 	       zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL;
322 }
323 
324 /**
325  * zpool_map_handle() - Map a previously allocated handle into memory
326  * @zpool:	The zpool that the handle was allocated from
327  * @handle:	The handle to map
328  * @mapmode:	How the memory should be mapped
329  *
330  * This maps a previously allocated handle into memory.  The @mapmode
331  * param indicates to the implementation how the memory will be
332  * used, i.e. read-only, write-only, read-write.  If the
333  * implementation does not support it, the memory will be treated
334  * as read-write.
335  *
336  * This may hold locks, disable interrupts, and/or preemption,
337  * and the zpool_unmap_handle() must be called to undo those
338  * actions.  The code that uses the mapped handle should complete
339  * its operations on the mapped handle memory quickly and unmap
340  * as soon as possible.  As the implementation may use per-cpu
341  * data, multiple handles should not be mapped concurrently on
342  * any cpu.
343  *
344  * Returns: A pointer to the handle's mapped memory area.
345  */
zpool_map_handle(struct zpool * zpool,unsigned long handle,enum zpool_mapmode mapmode)346 void *zpool_map_handle(struct zpool *zpool, unsigned long handle,
347 			enum zpool_mapmode mapmode)
348 {
349 	return zpool->driver->map(zpool->pool, handle, mapmode);
350 }
351 
352 /**
353  * zpool_unmap_handle() - Unmap a previously mapped handle
354  * @zpool:	The zpool that the handle was allocated from
355  * @handle:	The handle to unmap
356  *
357  * This unmaps a previously mapped handle.  Any locks or other
358  * actions that the implementation took in zpool_map_handle()
359  * will be undone here.  The memory area returned from
360  * zpool_map_handle() should no longer be used after this.
361  */
zpool_unmap_handle(struct zpool * zpool,unsigned long handle)362 void zpool_unmap_handle(struct zpool *zpool, unsigned long handle)
363 {
364 	zpool->driver->unmap(zpool->pool, handle);
365 }
366 
367 /**
368  * zpool_get_total_size() - The total size of the pool
369  * @zpool:	The zpool to check
370  *
371  * This returns the total size in bytes of the pool.
372  *
373  * Returns: Total size of the zpool in bytes.
374  */
zpool_get_total_size(struct zpool * zpool)375 u64 zpool_get_total_size(struct zpool *zpool)
376 {
377 	return zpool->driver->total_size(zpool->pool);
378 }
379 
380 /**
381  * zpool_evictable() - Test if zpool is potentially evictable
382  * @zpool:	The zpool to test
383  *
384  * Zpool is only potentially evictable when it's created with struct
385  * zpool_ops.evict and its driver implements struct zpool_driver.shrink.
386  *
387  * However, it doesn't necessarily mean driver will use zpool_ops.evict
388  * in its implementation of zpool_driver.shrink. It could do internal
389  * defragmentation instead.
390  *
391  * Returns: true if potentially evictable; false otherwise.
392  */
zpool_evictable(struct zpool * zpool)393 bool zpool_evictable(struct zpool *zpool)
394 {
395 	return zpool->evictable;
396 }
397 
398 /**
399  * zpool_can_sleep_mapped - Test if zpool can sleep when do mapped.
400  * @zpool:	The zpool to test
401  *
402  * Returns: true if zpool can sleep; false otherwise.
403  */
zpool_can_sleep_mapped(struct zpool * zpool)404 bool zpool_can_sleep_mapped(struct zpool *zpool)
405 {
406 	return zpool->can_sleep_mapped;
407 }
408 
409 MODULE_LICENSE("GPL");
410 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
411 MODULE_DESCRIPTION("Common API for compressed memory storage");
412