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