xref: /openbmc/linux/mm/zpool.c (revision fce96cf0443083e37455eff8f78fd240c621dae3)
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   */
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   */
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. */
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  
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   */
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   */
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   */
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   */
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   */
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   */
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   */
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   */
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   */
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   */
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   */
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   */
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   */
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