smalloc.c - fp2-dev/platform/external/fio - Gitiles

 /*
  * simple memory allocator, backed by mmap() so that it hands out memory
  * that can be shared across processes and threads
  */
 #include <sys/mman.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <limits.h>

 #include "mutex.h"

 #define MP_SAFE			/* define to make thread safe */
 #define SMALLOC_REDZONE		/* define to detect memory corruption */

 #define SMALLOC_BPB	32	/* block size, bytes-per-bit in bitmap */
 #define SMALLOC_BPI	(sizeof(unsigned int) * 8)
 #define SMALLOC_BPL	(SMALLOC_BPB * SMALLOC_BPI)

 #define INITIAL_SIZE	1024*1024	/* new pool size */
 #define MAX_POOLS	4		/* maximum number of pools to setup */

 #define SMALLOC_PRE_RED		0xdeadbeefU
 #define SMALLOC_POST_RED	0x5aa55aa5U

 unsigned int smalloc_pool_size = INITIAL_SIZE;

 struct pool {
 	struct fio_mutex *lock;			/* protects this pool */
 	void *map;				/* map of blocks */
 	unsigned int *bitmap;			/* blocks free/busy map */
 	unsigned int free_blocks;		/* free blocks */
 	unsigned int nr_blocks;			/* total blocks */
 	unsigned int next_non_full;
 	int fd;					/* memory backing fd */
 	char file[PATH_MAX];			/* filename for fd */
 	unsigned int mmap_size;
 };

 struct block_hdr {
 	unsigned int size;
 #ifdef SMALLOC_REDZONE
 	unsigned int prered;
 #endif
 };

 static struct pool mp[MAX_POOLS];
 static unsigned int nr_pools;
 static unsigned int last_pool;
 static struct fio_mutex *lock;

 static inline void pool_lock(struct pool *pool)
 {
 	if (pool->lock)
 		fio_mutex_down(pool->lock);
 }

 static inline void pool_unlock(struct pool *pool)
 {
 	if (pool->lock)
 		fio_mutex_up(pool->lock);
 }

 static inline void global_read_lock(void)
 {
 	if (lock)
 		fio_mutex_down_read(lock);
 }

 static inline void global_read_unlock(void)
 {
 	if (lock)
 		fio_mutex_up_read(lock);
 }

 static inline void global_write_lock(void)
 {
 	if (lock)
 		fio_mutex_down_write(lock);
 }

 static inline void global_write_unlock(void)
 {
 	if (lock)
 		fio_mutex_up_write(lock);
 }

 static inline int ptr_valid(struct pool *pool, void *ptr)
 {
 	unsigned int pool_size = pool->nr_blocks * SMALLOC_BPL;

 	return (ptr >= pool->map) && (ptr < pool->map + pool_size);
 }

 static inline unsigned int size_to_blocks(unsigned int size)
 {
 	return (size + SMALLOC_BPB - 1) / SMALLOC_BPB;
 }

 static int blocks_iter(unsigned int *map, unsigned int idx,
 		       unsigned int nr_blocks,
 		       int (*func)(unsigned int *map, unsigned int mask))
 {
 	while (nr_blocks) {
 		unsigned int this_blocks, mask;

 		this_blocks = nr_blocks;
 		if (this_blocks + idx > SMALLOC_BPI) {
 			this_blocks = SMALLOC_BPI - idx;
 			idx = SMALLOC_BPI - this_blocks;
 		}

 		if (this_blocks == SMALLOC_BPI)
 			mask = -1U;
 		else
 			mask = ((1U << this_blocks) - 1) << idx;

 		if (!func(map, mask))
 			return 0;

 		nr_blocks -= this_blocks;
 		idx = 0;
 		map++;
 	}

 	return 1;
 }

 static int mask_cmp(unsigned int *map, unsigned int mask)
 {
 	return !(*map & mask);
 }

 static int mask_clear(unsigned int *map, unsigned int mask)
 {
 	*map &= ~mask;
 	return 1;
 }

 static int mask_set(unsigned int *map, unsigned int mask)
 {
 	*map |= mask;
 	return 1;
 }

 static int blocks_free(unsigned int *map, unsigned int idx,
 		       unsigned int nr_blocks)
 {
 	return blocks_iter(map, idx, nr_blocks, mask_cmp);
 }

 static void set_blocks(unsigned int *map, unsigned int idx,
 		       unsigned int nr_blocks)
 {
 	blocks_iter(map, idx, nr_blocks, mask_set);
 }

 static void clear_blocks(unsigned int *map, unsigned int idx,
 			 unsigned int nr_blocks)
 {
 	blocks_iter(map, idx, nr_blocks, mask_clear);
 }

 static inline int __ffs(int word)
 {
 	int r = 0;

 	if (!(word & 0xffff)) {
 		word >>= 16;
 		r += 16;
 	}
 	if (!(word & 0xff)) {
 		word >>= 8;
 		r += 8;
 	}
 	if (!(word & 0xf)) {
 		word >>= 4;
 		r += 4;
 	}
 	if (!(word & 3)) {
 		word >>= 2;
 		r += 2;
 	}
 	if (!(word & 1)) {
 		word >>= 1;
 		r += 1;
 	}

 	return r;
 }

 static int find_next_zero(int word, int start)
 {
 	assert(word != -1U);
 	word >>= (start + 1);
 	return __ffs(~word) + start + 1;
 }

 static int add_pool(struct pool *pool, unsigned int alloc_size)
 {
 	void *ptr;
 	int fd, bitmap_blocks;

 	strcpy(pool->file, "/tmp/.fio_smalloc.XXXXXX");
 	fd = mkstemp(pool->file);
 	if (fd < 0)
 		goto out_close;

 #ifdef SMALLOC_REDZONE
 	alloc_size += sizeof(unsigned int);
 #endif
 	alloc_size += sizeof(struct block_hdr);
 	if (alloc_size < INITIAL_SIZE)
 		alloc_size = INITIAL_SIZE;

 	/* round up to nearest full number of blocks */
 	alloc_size = (alloc_size + SMALLOC_BPL - 1) & ~(SMALLOC_BPL - 1);
 	bitmap_blocks = alloc_size / SMALLOC_BPL;
 	alloc_size += bitmap_blocks * sizeof(unsigned int);
 	pool->mmap_size = alloc_size;

 	pool->nr_blocks = bitmap_blocks;
 	pool->free_blocks = bitmap_blocks * SMALLOC_BPB;

 	if (ftruncate(fd, alloc_size) < 0)
 		goto out_unlink;

 	ptr = mmap(NULL, alloc_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
 	if (ptr == MAP_FAILED)
 		goto out_unlink;

 	memset(ptr, 0, alloc_size);
 	pool->map = ptr;
 	pool->bitmap = (void *) ptr + (pool->nr_blocks * SMALLOC_BPL);

 #ifdef MP_SAFE
 	pool->lock = fio_mutex_init(1);
 	if (!pool->lock)
 		goto out_unlink;
 #endif

 	pool->fd = fd;

 	global_write_lock();
 	nr_pools++;
 	global_write_unlock();
 	return 0;
 out_unlink:
 	fprintf(stderr, "smalloc: failed adding pool\n");
 	if (pool->map)
 		munmap(pool->map, pool->mmap_size);
 	unlink(pool->file);
 out_close:
 	if (fd >= 0)
 		close(fd);
 	return 1;
 }

 void sinit(void)
 {
 	int ret;

 #ifdef MP_SAFE
 	lock = fio_mutex_rw_init();
 #endif
 	ret = add_pool(&mp[0], INITIAL_SIZE);
 	assert(!ret);
 }

 static void cleanup_pool(struct pool *pool)
 {
 	unlink(pool->file);
 	close(pool->fd);
 	munmap(pool->map, pool->mmap_size);

 	if (pool->lock)
 		fio_mutex_remove(pool->lock);
 }

 void scleanup(void)
 {
 	unsigned int i;

 	for (i = 0; i < nr_pools; i++)
 		cleanup_pool(&mp[i]);

 	if (lock)
 		fio_mutex_remove(lock);
 }

 static void fill_redzone(struct block_hdr *hdr)
 {
 #ifdef SMALLOC_REDZONE
 	unsigned int *postred = (void *) hdr + hdr->size - sizeof(unsigned int);

 	hdr->prered = SMALLOC_PRE_RED;
 	*postred = SMALLOC_POST_RED;
 #endif
 }

 static void sfree_check_redzone(struct block_hdr *hdr)
 {
 #ifdef SMALLOC_REDZONE
 	unsigned int *postred = (void *) hdr + hdr->size - sizeof(unsigned int);

 	if (hdr->prered != SMALLOC_PRE_RED) {
 		fprintf(stderr, "smalloc pre redzone destroyed!\n");
 		fprintf(stderr, "  ptr=%p, prered=%x, expected %x\n",
 				hdr, hdr->prered, SMALLOC_PRE_RED);
 		assert(0);
 	}
 	if (*postred != SMALLOC_POST_RED) {
 		fprintf(stderr, "smalloc post redzone destroyed!\n");
 		fprintf(stderr, "  ptr=%p, postred=%x, expected %x\n",
 				hdr, *postred, SMALLOC_POST_RED);
 		assert(0);
 	}
 #endif
 }

 static void sfree_pool(struct pool *pool, void *ptr)
 {
 	struct block_hdr *hdr;
 	unsigned int i, idx;
 	unsigned long offset;

 	if (!ptr)
 		return;

 	ptr -= sizeof(*hdr);
 	hdr = ptr;

 	assert(ptr_valid(pool, ptr));

 	sfree_check_redzone(hdr);

 	offset = ptr - pool->map;
 	i = offset / SMALLOC_BPL;
 	idx = (offset % SMALLOC_BPL) / SMALLOC_BPB;

 	pool_lock(pool);
 	clear_blocks(&pool->bitmap[i], idx, size_to_blocks(hdr->size));
 	if (i < pool->next_non_full)
 		pool->next_non_full = i;
 	pool->free_blocks += size_to_blocks(hdr->size);
 	pool_unlock(pool);
 }

 void sfree(void *ptr)
 {
 	struct pool *pool = NULL;
 	unsigned int i;

 	if (!ptr)
 		return;

 	global_read_lock();

 	for (i = 0; i < nr_pools; i++) {
 		if (ptr_valid(&mp[i], ptr)) {
 			pool = &mp[i];
 			break;
 		}
 	}

 	global_read_unlock();

 	assert(pool);
 	sfree_pool(pool, ptr);
 }

 static void *__smalloc_pool(struct pool *pool, unsigned int size)
 {
 	unsigned int nr_blocks;
 	unsigned int i;
 	unsigned int offset;
 	unsigned int last_idx;
 	void *ret = NULL;

 	pool_lock(pool);

 	nr_blocks = size_to_blocks(size);
 	if (nr_blocks > pool->free_blocks)
 		goto fail;

 	i = pool->next_non_full;
 	last_idx = 0;
 	offset = -1U;
 	while (i < pool->nr_blocks) {
 		unsigned int idx;

 		if (pool->bitmap[i] == -1U) {
 			i++;
 			pool->next_non_full = i;
 			last_idx = 0;
 			continue;
 		}

 		idx = find_next_zero(pool->bitmap[i], last_idx);
 		if (!blocks_free(&pool->bitmap[i], idx, nr_blocks)) {
 			idx += nr_blocks;
 			if (idx < SMALLOC_BPI)
 				last_idx = idx;
 			else {
 				last_idx = 0;
 				while (idx >= SMALLOC_BPI) {
 					i++;
 					idx -= SMALLOC_BPI;
 				}
 			}
 			continue;
 		}
 		set_blocks(&pool->bitmap[i], idx, nr_blocks);
 		offset = i * SMALLOC_BPL + idx * SMALLOC_BPB;
 		break;
 	}

 	if (i < pool->nr_blocks) {
 		pool->free_blocks -= nr_blocks;
 		ret = pool->map + offset;
 	}
 fail:
 	pool_unlock(pool);
 	return ret;
 }

 static void *smalloc_pool(struct pool *pool, unsigned int size)
 {
 	struct block_hdr *hdr;
 	unsigned int alloc_size;
 	void *ptr;

 	alloc_size = size + sizeof(*hdr);
 #ifdef SMALLOC_REDZONE
 	alloc_size += sizeof(unsigned int);
 #endif

 	ptr = __smalloc_pool(pool, alloc_size);
 	if (!ptr) {
 		printf("failed allocating %u\n", alloc_size);
 		return NULL;
 	}

 	hdr = ptr;
 	hdr->size = alloc_size;
 	ptr += sizeof(*hdr);

 	fill_redzone(hdr);

 	memset(ptr, 0, size);
 	return ptr;
 }

 void *smalloc(unsigned int size)
 {
 	unsigned int i;

 	global_read_lock();
 	i = last_pool;

 	do {
 		for (; i < nr_pools; i++) {
 			void *ptr = smalloc_pool(&mp[i], size);

 			if (ptr) {
 				last_pool = i;
 				global_read_unlock();
 				return ptr;
 			}
 		}
 		if (last_pool) {
 			last_pool = 0;
 			continue;
 		}

 		if (nr_pools + 1 > MAX_POOLS)
 			break;
 		else {
 			i = nr_pools;
 			global_read_unlock();
 			if (add_pool(&mp[nr_pools], size))
 				goto out;
 			global_read_lock();
 		}
 	} while (1);

 	global_read_unlock();
 out:
 	return NULL;
 }

 char *smalloc_strdup(const char *str)
 {
 	char *ptr;

 	ptr = smalloc(strlen(str) + 1);
 	strcpy(ptr, str);
 	return ptr;
 }
	/*
	* simple memory allocator, backed by mmap() so that it hands out memory
	* that can be shared across processes and threads
	*/
	#include <sys/mman.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <assert.h>
	#include <string.h>
	#include <unistd.h>
	#include <sys/types.h>
	#include <limits.h>

	#include "mutex.h"

	#define MP_SAFE /* define to make thread safe */
	#define SMALLOC_REDZONE /* define to detect memory corruption */

	#define SMALLOC_BPB 32 /* block size, bytes-per-bit in bitmap */
	#define SMALLOC_BPI (sizeof(unsigned int) * 8)
	#define SMALLOC_BPL (SMALLOC_BPB * SMALLOC_BPI)

	#define INITIAL_SIZE 10241024 / new pool size */
	#define MAX_POOLS 4 /* maximum number of pools to setup */

	#define SMALLOC_PRE_RED 0xdeadbeefU
	#define SMALLOC_POST_RED 0x5aa55aa5U

	unsigned int smalloc_pool_size = INITIAL_SIZE;

	struct pool {
	struct fio_mutex lock; / protects this pool */
	void map; / map of blocks */
	unsigned int bitmap; / blocks free/busy map */
	unsigned int free_blocks; /* free blocks */
	unsigned int nr_blocks; /* total blocks */
	unsigned int next_non_full;
	int fd; /* memory backing fd */
	char file[PATH_MAX]; /* filename for fd */
	unsigned int mmap_size;
	};

	struct block_hdr {
	unsigned int size;
	#ifdef SMALLOC_REDZONE
	unsigned int prered;
	#endif
	};

	static struct pool mp[MAX_POOLS];
	static unsigned int nr_pools;
	static unsigned int last_pool;
	static struct fio_mutex *lock;

	static inline void pool_lock(struct pool *pool)
	{
	if (pool->lock)
	fio_mutex_down(pool->lock);
	}

	static inline void pool_unlock(struct pool *pool)
	{
	if (pool->lock)
	fio_mutex_up(pool->lock);
	}

	static inline void global_read_lock(void)
	{
	if (lock)
	fio_mutex_down_read(lock);
	}

	static inline void global_read_unlock(void)
	{
	if (lock)
	fio_mutex_up_read(lock);
	}

	static inline void global_write_lock(void)
	{
	if (lock)
	fio_mutex_down_write(lock);
	}

	static inline void global_write_unlock(void)
	{
	if (lock)
	fio_mutex_up_write(lock);
	}

	static inline int ptr_valid(struct pool pool, void ptr)
	{
	unsigned int pool_size = pool->nr_blocks * SMALLOC_BPL;

	return (ptr >= pool->map) && (ptr < pool->map + pool_size);
	}

	static inline unsigned int size_to_blocks(unsigned int size)
	{
	return (size + SMALLOC_BPB - 1) / SMALLOC_BPB;
	}

	static int blocks_iter(unsigned int *map, unsigned int idx,
	unsigned int nr_blocks,
	int (func)(unsigned int map, unsigned int mask))
	{
	while (nr_blocks) {
	unsigned int this_blocks, mask;

	this_blocks = nr_blocks;
	if (this_blocks + idx > SMALLOC_BPI) {
	this_blocks = SMALLOC_BPI - idx;
	idx = SMALLOC_BPI - this_blocks;
	}

	if (this_blocks == SMALLOC_BPI)
	mask = -1U;
	else
	mask = ((1U << this_blocks) - 1) << idx;

	if (!func(map, mask))
	return 0;

	nr_blocks -= this_blocks;
	idx = 0;
	map++;
	}

	return 1;
	}

	static int mask_cmp(unsigned int *map, unsigned int mask)
	{
	return !(*map & mask);
	}

	static int mask_clear(unsigned int *map, unsigned int mask)
	{
	*map &= ~mask;
	return 1;
	}

	static int mask_set(unsigned int *map, unsigned int mask)
	{
	*map \|= mask;
	return 1;
	}

	static int blocks_free(unsigned int *map, unsigned int idx,
	unsigned int nr_blocks)
	{
	return blocks_iter(map, idx, nr_blocks, mask_cmp);
	}

	static void set_blocks(unsigned int *map, unsigned int idx,
	unsigned int nr_blocks)
	{
	blocks_iter(map, idx, nr_blocks, mask_set);
	}

	static void clear_blocks(unsigned int *map, unsigned int idx,
	unsigned int nr_blocks)
	{
	blocks_iter(map, idx, nr_blocks, mask_clear);
	}

	static inline int __ffs(int word)
	{
	int r = 0;

	if (!(word & 0xffff)) {
	word >>= 16;
	r += 16;
	}
	if (!(word & 0xff)) {
	word >>= 8;
	r += 8;
	}
	if (!(word & 0xf)) {
	word >>= 4;
	r += 4;
	}
	if (!(word & 3)) {
	word >>= 2;
	r += 2;
	}
	if (!(word & 1)) {
	word >>= 1;
	r += 1;
	}

	return r;
	}

	static int find_next_zero(int word, int start)
	{
	assert(word != -1U);
	word >>= (start + 1);
	return __ffs(~word) + start + 1;
	}

	static int add_pool(struct pool *pool, unsigned int alloc_size)
	{
	void *ptr;
	int fd, bitmap_blocks;

	strcpy(pool->file, "/tmp/.fio_smalloc.XXXXXX");
	fd = mkstemp(pool->file);
	if (fd < 0)
	goto out_close;

	#ifdef SMALLOC_REDZONE
	alloc_size += sizeof(unsigned int);
	#endif
	alloc_size += sizeof(struct block_hdr);
	if (alloc_size < INITIAL_SIZE)
	alloc_size = INITIAL_SIZE;

	/* round up to nearest full number of blocks */
	alloc_size = (alloc_size + SMALLOC_BPL - 1) & ~(SMALLOC_BPL - 1);
	bitmap_blocks = alloc_size / SMALLOC_BPL;
	alloc_size += bitmap_blocks * sizeof(unsigned int);
	pool->mmap_size = alloc_size;

	pool->nr_blocks = bitmap_blocks;
	pool->free_blocks = bitmap_blocks * SMALLOC_BPB;

	if (ftruncate(fd, alloc_size) < 0)
	goto out_unlink;

	ptr = mmap(NULL, alloc_size, PROT_READ\|PROT_WRITE, MAP_SHARED, fd, 0);
	if (ptr == MAP_FAILED)
	goto out_unlink;

	memset(ptr, 0, alloc_size);
	pool->map = ptr;
	pool->bitmap = (void ) ptr + (pool->nr_blocks SMALLOC_BPL);

	#ifdef MP_SAFE
	pool->lock = fio_mutex_init(1);
	if (!pool->lock)
	goto out_unlink;
	#endif

	pool->fd = fd;

	global_write_lock();
	nr_pools++;
	global_write_unlock();
	return 0;
	out_unlink:
	fprintf(stderr, "smalloc: failed adding pool\n");
	if (pool->map)
	munmap(pool->map, pool->mmap_size);
	unlink(pool->file);
	out_close:
	if (fd >= 0)
	close(fd);
	return 1;
	}

	void sinit(void)
	{
	int ret;

	#ifdef MP_SAFE
	lock = fio_mutex_rw_init();
	#endif
	ret = add_pool(&mp[0], INITIAL_SIZE);
	assert(!ret);
	}

	static void cleanup_pool(struct pool *pool)
	{
	unlink(pool->file);
	close(pool->fd);
	munmap(pool->map, pool->mmap_size);

	if (pool->lock)
	fio_mutex_remove(pool->lock);
	}

	void scleanup(void)
	{
	unsigned int i;

	for (i = 0; i < nr_pools; i++)
	cleanup_pool(&mp[i]);

	if (lock)
	fio_mutex_remove(lock);
	}

	static void fill_redzone(struct block_hdr *hdr)
	{
	#ifdef SMALLOC_REDZONE
	unsigned int postred = (void ) hdr + hdr->size - sizeof(unsigned int);

	hdr->prered = SMALLOC_PRE_RED;
	*postred = SMALLOC_POST_RED;
	#endif
	}

	static void sfree_check_redzone(struct block_hdr *hdr)
	{
	#ifdef SMALLOC_REDZONE
	unsigned int postred = (void ) hdr + hdr->size - sizeof(unsigned int);

	if (hdr->prered != SMALLOC_PRE_RED) {
	fprintf(stderr, "smalloc pre redzone destroyed!\n");
	fprintf(stderr, " ptr=%p, prered=%x, expected %x\n",
	hdr, hdr->prered, SMALLOC_PRE_RED);
	assert(0);
	}
	if (*postred != SMALLOC_POST_RED) {
	fprintf(stderr, "smalloc post redzone destroyed!\n");
	fprintf(stderr, " ptr=%p, postred=%x, expected %x\n",
	hdr, *postred, SMALLOC_POST_RED);
	assert(0);
	}
	#endif
	}

	static void sfree_pool(struct pool pool, void ptr)
	{
	struct block_hdr *hdr;
	unsigned int i, idx;
	unsigned long offset;

	if (!ptr)
	return;

	ptr -= sizeof(*hdr);
	hdr = ptr;

	assert(ptr_valid(pool, ptr));

	sfree_check_redzone(hdr);

	offset = ptr - pool->map;
	i = offset / SMALLOC_BPL;
	idx = (offset % SMALLOC_BPL) / SMALLOC_BPB;

	pool_lock(pool);
	clear_blocks(&pool->bitmap[i], idx, size_to_blocks(hdr->size));
	if (i < pool->next_non_full)
	pool->next_non_full = i;
	pool->free_blocks += size_to_blocks(hdr->size);
	pool_unlock(pool);
	}

	void sfree(void *ptr)
	{
	struct pool *pool = NULL;
	unsigned int i;

	if (!ptr)
	return;

	global_read_lock();

	for (i = 0; i < nr_pools; i++) {
	if (ptr_valid(&mp[i], ptr)) {
	pool = &mp[i];
	break;
	}
	}

	global_read_unlock();

	assert(pool);
	sfree_pool(pool, ptr);
	}

	static void __smalloc_pool(struct pool pool, unsigned int size)
	{
	unsigned int nr_blocks;
	unsigned int i;
	unsigned int offset;
	unsigned int last_idx;
	void *ret = NULL;

	pool_lock(pool);

	nr_blocks = size_to_blocks(size);
	if (nr_blocks > pool->free_blocks)
	goto fail;

	i = pool->next_non_full;
	last_idx = 0;
	offset = -1U;
	while (i < pool->nr_blocks) {
	unsigned int idx;

	if (pool->bitmap[i] == -1U) {
	i++;
	pool->next_non_full = i;
	last_idx = 0;
	continue;
	}

	idx = find_next_zero(pool->bitmap[i], last_idx);
	if (!blocks_free(&pool->bitmap[i], idx, nr_blocks)) {
	idx += nr_blocks;
	if (idx < SMALLOC_BPI)
	last_idx = idx;
	else {
	last_idx = 0;
	while (idx >= SMALLOC_BPI) {
	i++;
	idx -= SMALLOC_BPI;
	}
	}
	continue;
	}
	set_blocks(&pool->bitmap[i], idx, nr_blocks);
	offset = i * SMALLOC_BPL + idx * SMALLOC_BPB;
	break;
	}

	if (i < pool->nr_blocks) {
	pool->free_blocks -= nr_blocks;
	ret = pool->map + offset;
	}
	fail:
	pool_unlock(pool);
	return ret;
	}

	static void smalloc_pool(struct pool pool, unsigned int size)
	{
	struct block_hdr *hdr;
	unsigned int alloc_size;
	void *ptr;

	alloc_size = size + sizeof(*hdr);
	#ifdef SMALLOC_REDZONE
	alloc_size += sizeof(unsigned int);
	#endif

	ptr = __smalloc_pool(pool, alloc_size);
	if (!ptr) {
	printf("failed allocating %u\n", alloc_size);
	return NULL;
	}

	hdr = ptr;
	hdr->size = alloc_size;
	ptr += sizeof(*hdr);

	fill_redzone(hdr);

	memset(ptr, 0, size);
	return ptr;
	}

	void *smalloc(unsigned int size)
	{
	unsigned int i;

	global_read_lock();
	i = last_pool;

	do {
	for (; i < nr_pools; i++) {
	void *ptr = smalloc_pool(&mp[i], size);

	if (ptr) {
	last_pool = i;
	global_read_unlock();
	return ptr;
	}
	}
	if (last_pool) {
	last_pool = 0;
	continue;
	}

	if (nr_pools + 1 > MAX_POOLS)
	break;
	else {
	i = nr_pools;
	global_read_unlock();
	if (add_pool(&mp[nr_pools], size))
	goto out;
	global_read_lock();
	}
	} while (1);

	global_read_unlock();
	out:
	return NULL;
	}

	char smalloc_strdup(const char str)
	{
	char *ptr;

	ptr = smalloc(strlen(str) + 1);
	strcpy(ptr, str);
	return ptr;
	}