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