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TOMOYO Linux Cross Reference
Linux/lib/genalloc.c

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  1 /*
  2  * Basic general purpose allocator for managing special purpose
  3  * memory, for example, memory that is not managed by the regular
  4  * kmalloc/kfree interface.  Uses for this includes on-device special
  5  * memory, uncached memory etc.
  6  *
  7  * It is safe to use the allocator in NMI handlers and other special
  8  * unblockable contexts that could otherwise deadlock on locks.  This
  9  * is implemented by using atomic operations and retries on any
 10  * conflicts.  The disadvantage is that there may be livelocks in
 11  * extreme cases.  For better scalability, one allocator can be used
 12  * for each CPU.
 13  *
 14  * The lockless operation only works if there is enough memory
 15  * available.  If new memory is added to the pool a lock has to be
 16  * still taken.  So any user relying on locklessness has to ensure
 17  * that sufficient memory is preallocated.
 18  *
 19  * The basic atomic operation of this allocator is cmpxchg on long.
 20  * On architectures that don't have NMI-safe cmpxchg implementation,
 21  * the allocator can NOT be used in NMI handler.  So code uses the
 22  * allocator in NMI handler should depend on
 23  * CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
 24  *
 25  * Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
 26  *
 27  * This source code is licensed under the GNU General Public License,
 28  * Version 2.  See the file COPYING for more details.
 29  */
 30 
 31 #include <linux/slab.h>
 32 #include <linux/export.h>
 33 #include <linux/bitmap.h>
 34 #include <linux/rculist.h>
 35 #include <linux/interrupt.h>
 36 #include <linux/genalloc.h>
 37 
 38 static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
 39 {
 40         unsigned long val, nval;
 41 
 42         nval = *addr;
 43         do {
 44                 val = nval;
 45                 if (val & mask_to_set)
 46                         return -EBUSY;
 47                 cpu_relax();
 48         } while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);
 49 
 50         return 0;
 51 }
 52 
 53 static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
 54 {
 55         unsigned long val, nval;
 56 
 57         nval = *addr;
 58         do {
 59                 val = nval;
 60                 if ((val & mask_to_clear) != mask_to_clear)
 61                         return -EBUSY;
 62                 cpu_relax();
 63         } while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);
 64 
 65         return 0;
 66 }
 67 
 68 /*
 69  * bitmap_set_ll - set the specified number of bits at the specified position
 70  * @map: pointer to a bitmap
 71  * @start: a bit position in @map
 72  * @nr: number of bits to set
 73  *
 74  * Set @nr bits start from @start in @map lock-lessly. Several users
 75  * can set/clear the same bitmap simultaneously without lock. If two
 76  * users set the same bit, one user will return remain bits, otherwise
 77  * return 0.
 78  */
 79 static int bitmap_set_ll(unsigned long *map, int start, int nr)
 80 {
 81         unsigned long *p = map + BIT_WORD(start);
 82         const int size = start + nr;
 83         int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
 84         unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
 85 
 86         while (nr - bits_to_set >= 0) {
 87                 if (set_bits_ll(p, mask_to_set))
 88                         return nr;
 89                 nr -= bits_to_set;
 90                 bits_to_set = BITS_PER_LONG;
 91                 mask_to_set = ~0UL;
 92                 p++;
 93         }
 94         if (nr) {
 95                 mask_to_set &= BITMAP_LAST_WORD_MASK(size);
 96                 if (set_bits_ll(p, mask_to_set))
 97                         return nr;
 98         }
 99 
100         return 0;
101 }
102 
103 /*
104  * bitmap_clear_ll - clear the specified number of bits at the specified position
105  * @map: pointer to a bitmap
106  * @start: a bit position in @map
107  * @nr: number of bits to set
108  *
109  * Clear @nr bits start from @start in @map lock-lessly. Several users
110  * can set/clear the same bitmap simultaneously without lock. If two
111  * users clear the same bit, one user will return remain bits,
112  * otherwise return 0.
113  */
114 static int bitmap_clear_ll(unsigned long *map, int start, int nr)
115 {
116         unsigned long *p = map + BIT_WORD(start);
117         const int size = start + nr;
118         int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
119         unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
120 
121         while (nr - bits_to_clear >= 0) {
122                 if (clear_bits_ll(p, mask_to_clear))
123                         return nr;
124                 nr -= bits_to_clear;
125                 bits_to_clear = BITS_PER_LONG;
126                 mask_to_clear = ~0UL;
127                 p++;
128         }
129         if (nr) {
130                 mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
131                 if (clear_bits_ll(p, mask_to_clear))
132                         return nr;
133         }
134 
135         return 0;
136 }
137 
138 /**
139  * gen_pool_create - create a new special memory pool
140  * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
141  * @nid: node id of the node the pool structure should be allocated on, or -1
142  *
143  * Create a new special memory pool that can be used to manage special purpose
144  * memory not managed by the regular kmalloc/kfree interface.
145  */
146 struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
147 {
148         struct gen_pool *pool;
149 
150         pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
151         if (pool != NULL) {
152                 spin_lock_init(&pool->lock);
153                 INIT_LIST_HEAD(&pool->chunks);
154                 pool->min_alloc_order = min_alloc_order;
155         }
156         return pool;
157 }
158 EXPORT_SYMBOL(gen_pool_create);
159 
160 /**
161  * gen_pool_add_virt - add a new chunk of special memory to the pool
162  * @pool: pool to add new memory chunk to
163  * @virt: virtual starting address of memory chunk to add to pool
164  * @phys: physical starting address of memory chunk to add to pool
165  * @size: size in bytes of the memory chunk to add to pool
166  * @nid: node id of the node the chunk structure and bitmap should be
167  *       allocated on, or -1
168  *
169  * Add a new chunk of special memory to the specified pool.
170  *
171  * Returns 0 on success or a -ve errno on failure.
172  */
173 int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
174                  size_t size, int nid)
175 {
176         struct gen_pool_chunk *chunk;
177         int nbits = size >> pool->min_alloc_order;
178         int nbytes = sizeof(struct gen_pool_chunk) +
179                                 (nbits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;
180 
181         chunk = kmalloc_node(nbytes, GFP_KERNEL | __GFP_ZERO, nid);
182         if (unlikely(chunk == NULL))
183                 return -ENOMEM;
184 
185         chunk->phys_addr = phys;
186         chunk->start_addr = virt;
187         chunk->end_addr = virt + size;
188         atomic_set(&chunk->avail, size);
189 
190         spin_lock(&pool->lock);
191         list_add_rcu(&chunk->next_chunk, &pool->chunks);
192         spin_unlock(&pool->lock);
193 
194         return 0;
195 }
196 EXPORT_SYMBOL(gen_pool_add_virt);
197 
198 /**
199  * gen_pool_virt_to_phys - return the physical address of memory
200  * @pool: pool to allocate from
201  * @addr: starting address of memory
202  *
203  * Returns the physical address on success, or -1 on error.
204  */
205 phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
206 {
207         struct gen_pool_chunk *chunk;
208         phys_addr_t paddr = -1;
209 
210         rcu_read_lock();
211         list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
212                 if (addr >= chunk->start_addr && addr < chunk->end_addr) {
213                         paddr = chunk->phys_addr + (addr - chunk->start_addr);
214                         break;
215                 }
216         }
217         rcu_read_unlock();
218 
219         return paddr;
220 }
221 EXPORT_SYMBOL(gen_pool_virt_to_phys);
222 
223 /**
224  * gen_pool_destroy - destroy a special memory pool
225  * @pool: pool to destroy
226  *
227  * Destroy the specified special memory pool. Verifies that there are no
228  * outstanding allocations.
229  */
230 void gen_pool_destroy(struct gen_pool *pool)
231 {
232         struct list_head *_chunk, *_next_chunk;
233         struct gen_pool_chunk *chunk;
234         int order = pool->min_alloc_order;
235         int bit, end_bit;
236 
237         list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
238                 chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
239                 list_del(&chunk->next_chunk);
240 
241                 end_bit = (chunk->end_addr - chunk->start_addr) >> order;
242                 bit = find_next_bit(chunk->bits, end_bit, 0);
243                 BUG_ON(bit < end_bit);
244 
245                 kfree(chunk);
246         }
247         kfree(pool);
248         return;
249 }
250 EXPORT_SYMBOL(gen_pool_destroy);
251 
252 /**
253  * gen_pool_alloc - allocate special memory from the pool
254  * @pool: pool to allocate from
255  * @size: number of bytes to allocate from the pool
256  *
257  * Allocate the requested number of bytes from the specified pool.
258  * Uses a first-fit algorithm. Can not be used in NMI handler on
259  * architectures without NMI-safe cmpxchg implementation.
260  */
261 unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
262 {
263         struct gen_pool_chunk *chunk;
264         unsigned long addr = 0;
265         int order = pool->min_alloc_order;
266         int nbits, start_bit = 0, end_bit, remain;
267 
268 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
269         BUG_ON(in_nmi());
270 #endif
271 
272         if (size == 0)
273                 return 0;
274 
275         nbits = (size + (1UL << order) - 1) >> order;
276         rcu_read_lock();
277         list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
278                 if (size > atomic_read(&chunk->avail))
279                         continue;
280 
281                 end_bit = (chunk->end_addr - chunk->start_addr) >> order;
282 retry:
283                 start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit,
284                                                        start_bit, nbits, 0);
285                 if (start_bit >= end_bit)
286                         continue;
287                 remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
288                 if (remain) {
289                         remain = bitmap_clear_ll(chunk->bits, start_bit,
290                                                  nbits - remain);
291                         BUG_ON(remain);
292                         goto retry;
293                 }
294 
295                 addr = chunk->start_addr + ((unsigned long)start_bit << order);
296                 size = nbits << order;
297                 atomic_sub(size, &chunk->avail);
298                 break;
299         }
300         rcu_read_unlock();
301         return addr;
302 }
303 EXPORT_SYMBOL(gen_pool_alloc);
304 
305 /**
306  * gen_pool_free - free allocated special memory back to the pool
307  * @pool: pool to free to
308  * @addr: starting address of memory to free back to pool
309  * @size: size in bytes of memory to free
310  *
311  * Free previously allocated special memory back to the specified
312  * pool.  Can not be used in NMI handler on architectures without
313  * NMI-safe cmpxchg implementation.
314  */
315 void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
316 {
317         struct gen_pool_chunk *chunk;
318         int order = pool->min_alloc_order;
319         int start_bit, nbits, remain;
320 
321 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
322         BUG_ON(in_nmi());
323 #endif
324 
325         nbits = (size + (1UL << order) - 1) >> order;
326         rcu_read_lock();
327         list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
328                 if (addr >= chunk->start_addr && addr < chunk->end_addr) {
329                         BUG_ON(addr + size > chunk->end_addr);
330                         start_bit = (addr - chunk->start_addr) >> order;
331                         remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
332                         BUG_ON(remain);
333                         size = nbits << order;
334                         atomic_add(size, &chunk->avail);
335                         rcu_read_unlock();
336                         return;
337                 }
338         }
339         rcu_read_unlock();
340         BUG();
341 }
342 EXPORT_SYMBOL(gen_pool_free);
343 
344 /**
345  * gen_pool_for_each_chunk - call func for every chunk of generic memory pool
346  * @pool:       the generic memory pool
347  * @func:       func to call
348  * @data:       additional data used by @func
349  *
350  * Call @func for every chunk of generic memory pool.  The @func is
351  * called with rcu_read_lock held.
352  */
353 void gen_pool_for_each_chunk(struct gen_pool *pool,
354         void (*func)(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data),
355         void *data)
356 {
357         struct gen_pool_chunk *chunk;
358 
359         rcu_read_lock();
360         list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)
361                 func(pool, chunk, data);
362         rcu_read_unlock();
363 }
364 EXPORT_SYMBOL(gen_pool_for_each_chunk);
365 
366 /**
367  * gen_pool_avail - get available free space of the pool
368  * @pool: pool to get available free space
369  *
370  * Return available free space of the specified pool.
371  */
372 size_t gen_pool_avail(struct gen_pool *pool)
373 {
374         struct gen_pool_chunk *chunk;
375         size_t avail = 0;
376 
377         rcu_read_lock();
378         list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
379                 avail += atomic_read(&chunk->avail);
380         rcu_read_unlock();
381         return avail;
382 }
383 EXPORT_SYMBOL_GPL(gen_pool_avail);
384 
385 /**
386  * gen_pool_size - get size in bytes of memory managed by the pool
387  * @pool: pool to get size
388  *
389  * Return size in bytes of memory managed by the pool.
390  */
391 size_t gen_pool_size(struct gen_pool *pool)
392 {
393         struct gen_pool_chunk *chunk;
394         size_t size = 0;
395 
396         rcu_read_lock();
397         list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
398                 size += chunk->end_addr - chunk->start_addr;
399         rcu_read_unlock();
400         return size;
401 }
402 EXPORT_SYMBOL_GPL(gen_pool_size);
403 

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