[PATCH 4/9] lock-less general memory allocator

[Huang Ying]

Lock-less memory allocator, can be used to allocate/free memory in
IRQ/NMI handler. This is useful for hardware error handling, which
needs to collect hardware error information in IRQ/NMI handler.

The memory pages for lock-less memory allocator are pre-allocated
during initialization. Bitmap is used to record allocated/free memory
blocks. To support lock-less allocate/free operation, lock-less bitmap
set/clear operations are used.

The difference between this allocator and the gen_pool implementation
in lib/genalloc.c is that memory can be allocated/freed by multiple
users simultaneously without lock.

Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
---
 include/linux/llalloc.h |   27 +++++
 lib/Kconfig             |    3 
 lib/Makefile            |    1 
 lib/llalloc.c           |  259 ++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 290 insertions(+)
 create mode 100644 include/linux/llalloc.h
 create mode 100644 lib/llalloc.c

--- /dev/null
+++ b/include/linux/llalloc.h
@@ -0,0 +1,27 @@
+#ifndef LLALLOC_H
+#define LLALLOC_H
+
+struct ll_pool;
+
+struct ll_pool_chunk {
+	atomic_t avail;
+	void *data;
+	struct ll_pool *pool;
+	unsigned long bitmap[0];
+};
+
+struct ll_pool {
+	int min_alloc_order;
+	int chunk_order;
+	int chunk_num;
+	struct ll_pool_chunk *chunks[0];
+};
+
+struct ll_pool *ll_pool_create(int min_alloc_order, int chunk_order,
+			       int chunk_num, int nid);
+void ll_pool_destroy(struct ll_pool *pool);
+void *ll_pool_alloc(struct ll_pool *pool, size_t len);
+void ll_pool_free(const void *p, size_t len);
+size_t ll_pool_avail(struct ll_pool *pool);
+size_t ll_pool_size(struct ll_pool *pool);
+#endif /* LLALLOC_H */
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -213,4 +213,7 @@ config LRU_CACHE
 config LLIST
 	bool
 
+config LLALLOC
+	bool
+
 endmenu
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -107,6 +107,7 @@ obj-$(CONFIG_GENERIC_ATOMIC64) += atomic
 obj-$(CONFIG_ATOMIC64_SELFTEST) += atomic64_test.o
 
 obj-$(CONFIG_LLIST) += llist.o
+obj-$(CONFIG_LLALLOC) += llalloc.o
 
 hostprogs-y	:= gen_crc32table
 clean-files	:= crc32table.h
--- /dev/null
+++ b/lib/llalloc.c
@@ -0,0 +1,259 @@
+/*
+ * Lock-less memory allocator, This can be used to allocate/free
+ * memory in IRQ/NMI handler. This is useful for hardware error
+ * handling, which needs to collect hardware error information in
+ * IRQ/NMI handler.
+ *
+ * The memory pages for lock-less memory allocator are pre-allocated
+ * during initialization. Bitmap is used to record allocated/free
+ * memory blocks. To support lock-less allocate/free operation,
+ * lock-less bitmap set/clear operations are used.
+ *
+ * The difference between this allocator and the gen_pool
+ * implementation in lib/genalloc.c is that memory can be
+ * allocated/freed by multiple users simultaneously without lock.
+ *
+ * Copyright 2010 Intel Corp.
+ *   Author: Huang Ying <ying.huang@xxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/bitmap.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/llalloc.h>
+
+static inline void ll_page_set_chunk(struct page *page,
+				     struct ll_pool_chunk *chunk)
+{
+	page->lru.prev = (struct list_head *)chunk;
+}
+
+static inline struct ll_pool_chunk *ll_virt_to_pool_chunk(const void *p)
+{
+	struct page *page = virt_to_head_page(p);
+	return (struct ll_pool_chunk *)page->lru.prev;
+}
+
+static void ll_pool_chunk_destroy(struct ll_pool_chunk *chunk)
+{
+	int chunk_size = PAGE_SIZE << chunk->pool->chunk_order;
+
+	BUG_ON(atomic_read(&chunk->avail) != chunk_size);
+	__free_pages(virt_to_page(chunk->data), chunk->pool->chunk_order);
+	kfree(chunk);
+}
+
+/**
+ * ll_pool_destroy - destroy a lock-less memory pool
+ * @ pool: pool to destroy
+ *
+ * Destroy the lock-less memory pool. Verify that there are no
+ * outstanding allocations. Memory pages backed the lock-less
+ * allocator are freed.
+ */
+void ll_pool_destroy(struct ll_pool *pool)
+{
+	int i;
+
+	for (i = 0; i < pool->chunk_num; i++) {
+		if (pool->chunks[i])
+			ll_pool_chunk_destroy(pool->chunks[i]);
+	}
+}
+EXPORT_SYMBOL_GPL(ll_pool_destroy);
+
+static struct ll_pool_chunk *ll_pool_chunk_create(struct ll_pool *pool, int nid)
+{
+	struct ll_pool_chunk *chunk;
+	int chunk_size = PAGE_SIZE << pool->chunk_order;
+	int nbits = chunk_size >> pool->min_alloc_order;
+	int nbytes = sizeof(struct ll_pool_chunk) + \
+		DIV_ROUND_UP(nbits, BITS_PER_LONG) * sizeof(unsigned long);
+	struct page *page;
+
+	chunk = kmalloc_node(nbytes, GFP_KERNEL | __GFP_ZERO, nid);
+	if (!chunk)
+		return NULL;
+	page = alloc_pages_node(nid, GFP_KERNEL, pool->chunk_order);
+	if (!page)
+		goto err_free_chunk;
+	chunk->data = page_address(page);
+	atomic_set(&chunk->avail, chunk_size);
+	ll_page_set_chunk(page, chunk);
+	chunk->pool = pool;
+
+	return chunk;
+err_free_chunk:
+	kfree(chunk);
+	return NULL;
+}
+
+/**
+ * ll_pool_create - create a new lock-less memory pool
+ * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
+ * @chunk_order: log base 2 of number of pages each chunk manages
+ * @chunk_num: number of chunks
+ * @nid: node id of the node the pool structure should be allocated on, or -1
+ *
+ * Create a new lock-less memory pool that can be used in IRQ/NMI
+ * context. (PAGE_SIZE << @chunk_order) * @chunk_num memory pages
+ * backed the lock-less allocator are allocated with alloc_pages_node.
+ */
+struct ll_pool *ll_pool_create(int min_alloc_order, int chunk_order,
+			       int chunk_num, int nid)
+{
+	struct ll_pool *pool;
+	int i;
+
+	pool = kmalloc_node(sizeof(*pool) + chunk_num * sizeof(void *),
+			    GFP_KERNEL | __GFP_ZERO, nid);
+	if (!pool)
+		return NULL;
+	pool->min_alloc_order = min_alloc_order;
+	pool->chunk_order = chunk_order;
+	pool->chunk_num = chunk_num;
+	for (i = 0; i < chunk_num; i++) {
+		pool->chunks[i] = ll_pool_chunk_create(pool, nid);
+		if (!pool->chunks[i])
+			goto err_pool_destroy;
+	}
+
+	return pool;
+err_pool_destroy:
+	ll_pool_destroy(pool);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(ll_pool_create);
+
+static void *ll_pool_chunk_alloc(struct ll_pool_chunk *chunk, size_t len)
+{
+	struct ll_pool *pool = chunk->pool;
+	int order = pool->min_alloc_order;
+	int chunk_bits = (PAGE_SIZE << pool->chunk_order) >> order;
+	int pos = 0, bits, remain;
+
+	if (len > atomic_read(&chunk->avail))
+		return NULL;
+
+	bits = (len + (1UL << order) - 1) >> order;
+	for (;;) {
+		pos = bitmap_find_next_zero_area(chunk->bitmap, chunk_bits,
+						 pos, bits, 0);
+		if (pos >= chunk_bits)
+			return NULL;
+		remain = bitmap_set_ll(chunk->bitmap, pos, bits);
+		if (!remain)
+			break;
+		remain = bitmap_clear_ll(chunk->bitmap, pos, bits - remain);
+		BUG_ON(remain);
+	}
+	len = bits << order;
+	atomic_sub(len, &chunk->avail);
+
+	return chunk->data + (pos << order);
+}
+
+/**
+ * ll_pool_alloc - allocate memory from the pool
+ * @pool: pool to allocate from
+ * @len: number of bytes to allocate from the pool
+ *
+ * Allocate the required number of bytes from the pool. Uses a
+ * first-fit algorithm.
+ */
+void *ll_pool_alloc(struct ll_pool *pool, size_t len)
+{
+	int i;
+	void *p;
+	struct ll_pool_chunk *chunk;
+
+	for (i = 0; i < pool->chunk_num; i++) {
+		chunk = pool->chunks[i];
+		p = ll_pool_chunk_alloc(chunk, len);
+		if (p)
+			return p;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(ll_pool_alloc);
+
+static void ll_pool_chunk_free(struct ll_pool_chunk *chunk,
+			       const void *p, size_t len)
+{
+	struct ll_pool *pool = chunk->pool;
+	int order = pool->min_alloc_order;
+	int mask = (1UL << order) - 1;
+	int chunk_size = PAGE_SIZE << pool->chunk_order;
+	int remain, pos, bits;
+
+	BUG_ON(p < chunk->data || p + len > chunk->data + chunk_size);
+	BUG_ON((p - chunk->data) & mask);
+	bits = (len + mask) >> order;
+	len = bits << order;
+	pos = (p - chunk->data) >> order;
+	remain = bitmap_clear_ll(chunk->bitmap, pos, bits);
+	BUG_ON(remain);
+	atomic_add(len, &chunk->avail);
+}
+
+/**
+ * ll_pool_free - free allocated memory back to the pool
+ * @p: starting address of memory to free back to pool
+ * @len: size in bytes of memory to free
+ *
+ * Free previously allocated memory back the the pool.
+ */
+void ll_pool_free(const void *p, size_t len)
+{
+	struct ll_pool_chunk *chunk;
+
+	chunk = ll_virt_to_pool_chunk(p);
+	ll_pool_chunk_free(chunk, p, len);
+}
+EXPORT_SYMBOL_GPL(ll_pool_free);
+
+/**
+ * ll_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 ll_pool_avail(struct ll_pool *pool)
+{
+	int i;
+	size_t avail = 0;
+
+	for (i = 0; i < pool->chunk_num; i++)
+		avail += atomic_read(&pool->chunks[i]->avail);
+
+	return avail;
+}
+EXPORT_SYMBOL_GPL(ll_pool_avail);
+
+/**
+ * ll_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 ll_pool_size(struct ll_pool *pool)
+{
+	return (PAGE_SIZE << pool->chunk_order) * pool->chunk_num;
+}
+EXPORT_SYMBOL_GPL(ll_pool_size);
--
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