FreeBSD/Linux Kernel Cross Reference
sys/lib/genalloc.c

     /*
      * Basic general purpose allocator for managing special purpose
      * memory, for example, memory that is not managed by the regular
      * kmalloc/kfree interface.  Uses for this includes on-device special
      * memory, uncached memory etc.
      *
      * It is safe to use the allocator in NMI handlers and other special
      * unblockable contexts that could otherwise deadlock on locks.  This
      * is implemented by using atomic operations and retries on any
     * conflicts.  The disadvantage is that there may be livelocks in
     * extreme cases.  For better scalability, one allocator can be used
     * for each CPU.
     *
     * The lockless operation only works if there is enough memory
     * available.  If new memory is added to the pool a lock has to be
     * still taken.  So any user relying on locklessness has to ensure
     * that sufficient memory is preallocated.
     *
     * The basic atomic operation of this allocator is cmpxchg on long.
     * On architectures that don't have NMI-safe cmpxchg implementation,
     * the allocator can NOT be used in NMI handler.  So code uses the
     * allocator in NMI handler should depend on
     * CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
     *
     * Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
     *
     * This source code is licensed under the GNU General Public License,
     * Version 2.  See the file COPYING for more details.
     */
    
    #include <linux/slab.h>
    #include <linux/export.h>
    #include <linux/bitmap.h>
    #include <linux/rculist.h>
    #include <linux/interrupt.h>
    #include <linux/genalloc.h>
    
    static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
    {
            unsigned long val, nval;
    
            nval = *addr;
            do {
                    val = nval;
                    if (val & mask_to_set)
                            return -EBUSY;
                    cpu_relax();
            } while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);
    
            return 0;
    }
    
    static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
    {
            unsigned long val, nval;
    
            nval = *addr;
            do {
                    val = nval;
                    if ((val & mask_to_clear) != mask_to_clear)
                            return -EBUSY;
                    cpu_relax();
            } while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);
    
            return 0;
    }
    
    /*
     * bitmap_set_ll - set the specified number of bits at the specified position
     * @map: pointer to a bitmap
     * @start: a bit position in @map
     * @nr: number of bits to set
     *
     * Set @nr bits start from @start in @map lock-lessly. Several users
     * can set/clear the same bitmap simultaneously without lock. If two
     * users set the same bit, one user will return remain bits, otherwise
     * return 0.
     */
    static int bitmap_set_ll(unsigned long *map, int start, int nr)
    {
            unsigned long *p = map + BIT_WORD(start);
            const int size = start + nr;
            int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
            unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
    
            while (nr - bits_to_set >= 0) {
                    if (set_bits_ll(p, mask_to_set))
                            return nr;
                    nr -= bits_to_set;
                    bits_to_set = BITS_PER_LONG;
                    mask_to_set = ~0UL;
                    p++;
            }
            if (nr) {
                    mask_to_set &= BITMAP_LAST_WORD_MASK(size);
                    if (set_bits_ll(p, mask_to_set))
                            return nr;
            }
    
           return 0;
   }
   
   /*
    * bitmap_clear_ll - clear the specified number of bits at the specified position
    * @map: pointer to a bitmap
    * @start: a bit position in @map
    * @nr: number of bits to set
    *
    * Clear @nr bits start from @start in @map lock-lessly. Several users
    * can set/clear the same bitmap simultaneously without lock. If two
    * users clear the same bit, one user will return remain bits,
    * otherwise return 0.
    */
   static int bitmap_clear_ll(unsigned long *map, int start, int nr)
   {
           unsigned long *p = map + BIT_WORD(start);
           const int size = start + nr;
           int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
           unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
   
           while (nr - bits_to_clear >= 0) {
                   if (clear_bits_ll(p, mask_to_clear))
                           return nr;
                   nr -= bits_to_clear;
                   bits_to_clear = BITS_PER_LONG;
                   mask_to_clear = ~0UL;
                   p++;
           }
           if (nr) {
                   mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
                   if (clear_bits_ll(p, mask_to_clear))
                           return nr;
           }
   
           return 0;
   }
   
   /**
    * gen_pool_create - create a new special memory pool
    * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
    * @nid: node id of the node the pool structure should be allocated on, or -1
    *
    * Create a new special memory pool that can be used to manage special purpose
    * memory not managed by the regular kmalloc/kfree interface.
    */
   struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
   {
           struct gen_pool *pool;
   
           pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
           if (pool != NULL) {
                   spin_lock_init(&pool->lock);
                   INIT_LIST_HEAD(&pool->chunks);
                   pool->min_alloc_order = min_alloc_order;
                   pool->algo = gen_pool_first_fit;
                   pool->data = NULL;
           }
           return pool;
   }
   EXPORT_SYMBOL(gen_pool_create);
   
   /**
    * gen_pool_add_virt - add a new chunk of special memory to the pool
    * @pool: pool to add new memory chunk to
    * @virt: virtual starting address of memory chunk to add to pool
    * @phys: physical starting address of memory chunk to add to pool
    * @size: size in bytes of the memory chunk to add to pool
    * @nid: node id of the node the chunk structure and bitmap should be
    *       allocated on, or -1
    *
    * Add a new chunk of special memory to the specified pool.
    *
    * Returns 0 on success or a -ve errno on failure.
    */
   int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
                    size_t size, int nid)
   {
           struct gen_pool_chunk *chunk;
           int nbits = size >> pool->min_alloc_order;
           int nbytes = sizeof(struct gen_pool_chunk) +
                                   BITS_TO_LONGS(nbits) * sizeof(long);
   
           chunk = kmalloc_node(nbytes, GFP_KERNEL | __GFP_ZERO, nid);
           if (unlikely(chunk == NULL))
                   return -ENOMEM;
   
           chunk->phys_addr = phys;
           chunk->start_addr = virt;
           chunk->end_addr = virt + size;
           atomic_set(&chunk->avail, size);
   
           spin_lock(&pool->lock);
           list_add_rcu(&chunk->next_chunk, &pool->chunks);
           spin_unlock(&pool->lock);
   
           return 0;
   }
   EXPORT_SYMBOL(gen_pool_add_virt);
   
   /**
    * gen_pool_virt_to_phys - return the physical address of memory
    * @pool: pool to allocate from
    * @addr: starting address of memory
    *
    * Returns the physical address on success, or -1 on error.
    */
   phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
   {
           struct gen_pool_chunk *chunk;
           phys_addr_t paddr = -1;
   
           rcu_read_lock();
           list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
                   if (addr >= chunk->start_addr && addr < chunk->end_addr) {
                           paddr = chunk->phys_addr + (addr - chunk->start_addr);
                           break;
                   }
           }
           rcu_read_unlock();
   
           return paddr;
   }
   EXPORT_SYMBOL(gen_pool_virt_to_phys);
   
   /**
    * gen_pool_destroy - destroy a special memory pool
    * @pool: pool to destroy
    *
    * Destroy the specified special memory pool. Verifies that there are no
    * outstanding allocations.
    */
   void gen_pool_destroy(struct gen_pool *pool)
   {
           struct list_head *_chunk, *_next_chunk;
           struct gen_pool_chunk *chunk;
           int order = pool->min_alloc_order;
           int bit, end_bit;
   
           list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
                   chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
                   list_del(&chunk->next_chunk);
   
                   end_bit = (chunk->end_addr - chunk->start_addr) >> order;
                   bit = find_next_bit(chunk->bits, end_bit, 0);
                   BUG_ON(bit < end_bit);
   
                   kfree(chunk);
           }
           kfree(pool);
           return;
   }
   EXPORT_SYMBOL(gen_pool_destroy);
   
   /**
    * gen_pool_alloc - allocate special memory from the pool
    * @pool: pool to allocate from
    * @size: number of bytes to allocate from the pool
    *
    * Allocate the requested number of bytes from the specified pool.
    * Uses the pool allocation function (with first-fit algorithm by default).
    * Can not be used in NMI handler on architectures without
    * NMI-safe cmpxchg implementation.
    */
   unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
   {
           struct gen_pool_chunk *chunk;
           unsigned long addr = 0;
           int order = pool->min_alloc_order;
           int nbits, start_bit = 0, end_bit, remain;
   
   #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
           BUG_ON(in_nmi());
   #endif
   
           if (size == 0)
                   return 0;
   
           nbits = (size + (1UL << order) - 1) >> order;
           rcu_read_lock();
           list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
                   if (size > atomic_read(&chunk->avail))
                           continue;
   
                   end_bit = (chunk->end_addr - chunk->start_addr) >> order;
   retry:
                   start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
                                   pool->data);
                   if (start_bit >= end_bit)
                           continue;
                   remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
                   if (remain) {
                           remain = bitmap_clear_ll(chunk->bits, start_bit,
                                                    nbits - remain);
                           BUG_ON(remain);
                           goto retry;
                   }
   
                   addr = chunk->start_addr + ((unsigned long)start_bit << order);
                   size = nbits << order;
                   atomic_sub(size, &chunk->avail);
                   break;
           }
           rcu_read_unlock();
           return addr;
   }
   EXPORT_SYMBOL(gen_pool_alloc);
   
   /**
    * gen_pool_free - free allocated special memory back to the pool
    * @pool: pool to free to
    * @addr: starting address of memory to free back to pool
    * @size: size in bytes of memory to free
    *
    * Free previously allocated special memory back to the specified
    * pool.  Can not be used in NMI handler on architectures without
    * NMI-safe cmpxchg implementation.
    */
   void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
   {
           struct gen_pool_chunk *chunk;
           int order = pool->min_alloc_order;
           int start_bit, nbits, remain;
   
   #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
           BUG_ON(in_nmi());
   #endif
   
           nbits = (size + (1UL << order) - 1) >> order;
           rcu_read_lock();
           list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
                   if (addr >= chunk->start_addr && addr < chunk->end_addr) {
                           BUG_ON(addr + size > chunk->end_addr);
                           start_bit = (addr - chunk->start_addr) >> order;
                           remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
                           BUG_ON(remain);
                           size = nbits << order;
                           atomic_add(size, &chunk->avail);
                           rcu_read_unlock();
                           return;
                   }
           }
           rcu_read_unlock();
           BUG();
   }
   EXPORT_SYMBOL(gen_pool_free);
   
   /**
    * gen_pool_for_each_chunk - call func for every chunk of generic memory pool
    * @pool:       the generic memory pool
    * @func:       func to call
    * @data:       additional data used by @func
    *
    * Call @func for every chunk of generic memory pool.  The @func is
    * called with rcu_read_lock held.
    */
   void gen_pool_for_each_chunk(struct gen_pool *pool,
           void (*func)(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data),
           void *data)
   {
           struct gen_pool_chunk *chunk;
   
           rcu_read_lock();
           list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)
                   func(pool, chunk, data);
           rcu_read_unlock();
   }
   EXPORT_SYMBOL(gen_pool_for_each_chunk);
   
   /**
    * gen_pool_avail - get available free space of the pool
    * @pool: pool to get available free space
    *
    * Return available free space of the specified pool.
    */
   size_t gen_pool_avail(struct gen_pool *pool)
   {
           struct gen_pool_chunk *chunk;
           size_t avail = 0;
   
           rcu_read_lock();
           list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
                   avail += atomic_read(&chunk->avail);
           rcu_read_unlock();
           return avail;
   }
   EXPORT_SYMBOL_GPL(gen_pool_avail);
   
   /**
    * gen_pool_size - get size in bytes of memory managed by the pool
    * @pool: pool to get size
    *
    * Return size in bytes of memory managed by the pool.
    */
   size_t gen_pool_size(struct gen_pool *pool)
   {
           struct gen_pool_chunk *chunk;
           size_t size = 0;
   
           rcu_read_lock();
           list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
                   size += chunk->end_addr - chunk->start_addr;
           rcu_read_unlock();
           return size;
   }
   EXPORT_SYMBOL_GPL(gen_pool_size);
   
   /**
    * gen_pool_set_algo - set the allocation algorithm
    * @pool: pool to change allocation algorithm
    * @algo: custom algorithm function
    * @data: additional data used by @algo
    *
    * Call @algo for each memory allocation in the pool.
    * If @algo is NULL use gen_pool_first_fit as default
    * memory allocation function.
    */
   void gen_pool_set_algo(struct gen_pool *pool, genpool_algo_t algo, void *data)
   {
           rcu_read_lock();
   
           pool->algo = algo;
           if (!pool->algo)
                   pool->algo = gen_pool_first_fit;
   
           pool->data = data;
   
           rcu_read_unlock();
   }
   EXPORT_SYMBOL(gen_pool_set_algo);
   
   /**
    * gen_pool_first_fit - find the first available region
    * of memory matching the size requirement (no alignment constraint)
    * @map: The address to base the search on
    * @size: The bitmap size in bits
    * @start: The bitnumber to start searching at
    * @nr: The number of zeroed bits we're looking for
    * @data: additional data - unused
    */
   unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
                   unsigned long start, unsigned int nr, void *data)
   {
           return bitmap_find_next_zero_area(map, size, start, nr, 0);
   }
   EXPORT_SYMBOL(gen_pool_first_fit);
   
   /**
    * gen_pool_best_fit - find the best fitting region of memory
    * macthing the size requirement (no alignment constraint)
    * @map: The address to base the search on
    * @size: The bitmap size in bits
    * @start: The bitnumber to start searching at
    * @nr: The number of zeroed bits we're looking for
    * @data: additional data - unused
    *
    * Iterate over the bitmap to find the smallest free region
    * which we can allocate the memory.
    */
   unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
                   unsigned long start, unsigned int nr, void *data)
   {
           unsigned long start_bit = size;
           unsigned long len = size + 1;
           unsigned long index;
   
           index = bitmap_find_next_zero_area(map, size, start, nr, 0);
   
           while (index < size) {
                   int next_bit = find_next_bit(map, size, index + nr);
                   if ((next_bit - index) < len) {
                           len = next_bit - index;
                           start_bit = index;
                           if (len == nr)
                                   return start_bit;
                   }
                   index = bitmap_find_next_zero_area(map, size,
                                                      next_bit + 1, nr, 0);
           }
   
           return start_bit;
   }
   EXPORT_SYMBOL(gen_pool_best_fit);

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