--- /dev/null
+/*
+ * xvmalloc memory allocator
+ *
+ * Copyright (C) 2008, 2009, 2010 Nitin Gupta
+ *
+ * This code is released using a dual license strategy: BSD/GPL
+ * You can choose the licence that better fits your requirements.
+ *
+ * Released under the terms of 3-clause BSD License
+ * Released under the terms of GNU General Public License Version 2.0
+ */
+
+#ifdef CONFIG_ZRAM_DEBUG
+#define DEBUG
+#endif
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/bitops.h>
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+
+#include "xvmalloc.h"
+#include "xvmalloc_int.h"
+
+static void stat_inc(u64 *value)
+{
+ *value = *value + 1;
+}
+
+static void stat_dec(u64 *value)
+{
+ *value = *value - 1;
+}
+
+static int test_flag(struct block_header *block, enum blockflags flag)
+{
+ return block->prev & BIT(flag);
+}
+
+static void set_flag(struct block_header *block, enum blockflags flag)
+{
+ block->prev |= BIT(flag);
+}
+
+static void clear_flag(struct block_header *block, enum blockflags flag)
+{
+ block->prev &= ~BIT(flag);
+}
+
+/*
+ * Given <page, offset> pair, provide a dereferencable pointer.
+ * This is called from xv_malloc/xv_free path, so it
+ * needs to be fast.
+ */
+static void *get_ptr_atomic(struct page *page, u16 offset, enum km_type type)
+{
+ unsigned char *base;
+
+ base = kmap_atomic(page, type);
+ return base + offset;
+}
+
+static void put_ptr_atomic(void *ptr, enum km_type type)
+{
+ kunmap_atomic(ptr, type);
+}
+
+static u32 get_blockprev(struct block_header *block)
+{
+ return block->prev & PREV_MASK;
+}
+
+static void set_blockprev(struct block_header *block, u16 new_offset)
+{
+ block->prev = new_offset | (block->prev & FLAGS_MASK);
+}
+
+static struct block_header *BLOCK_NEXT(struct block_header *block)
+{
+ return (struct block_header *)
+ ((char *)block + block->size + XV_ALIGN);
+}
+
+/*
+ * Get index of free list containing blocks of maximum size
+ * which is less than or equal to given size.
+ */
+static u32 get_index_for_insert(u32 size)
+{
+ if (unlikely(size > XV_MAX_ALLOC_SIZE))
+ size = XV_MAX_ALLOC_SIZE;
+ size &= ~FL_DELTA_MASK;
+ return (size - XV_MIN_ALLOC_SIZE) >> FL_DELTA_SHIFT;
+}
+
+/*
+ * Get index of free list having blocks of size greater than
+ * or equal to requested size.
+ */
+static u32 get_index(u32 size)
+{
+ if (unlikely(size < XV_MIN_ALLOC_SIZE))
+ size = XV_MIN_ALLOC_SIZE;
+ size = ALIGN(size, FL_DELTA);
+ return (size - XV_MIN_ALLOC_SIZE) >> FL_DELTA_SHIFT;
+}
+
+/**
+ * find_block - find block of at least given size
+ * @pool: memory pool to search from
+ * @size: size of block required
+ * @page: page containing required block
+ * @offset: offset within the page where block is located.
+ *
+ * Searches two level bitmap to locate block of at least
+ * the given size. If such a block is found, it provides
+ * <page, offset> to identify this block and returns index
+ * in freelist where we found this block.
+ * Otherwise, returns 0 and <page, offset> params are not touched.
+ */
+static u32 find_block(struct xv_pool *pool, u32 size,
+ struct page **page, u32 *offset)
+{
+ ulong flbitmap, slbitmap;
+ u32 flindex, slindex, slbitstart;
+
+ /* There are no free blocks in this pool */
+ if (!pool->flbitmap)
+ return 0;
+
+ /* Get freelist index correspoding to this size */
+ slindex = get_index(size);
+ slbitmap = pool->slbitmap[slindex / BITS_PER_LONG];
+ slbitstart = slindex % BITS_PER_LONG;
+
+ /*
+ * If freelist is not empty at this index, we found the
+ * block - head of this list. This is approximate best-fit match.
+ */
+ if (test_bit(slbitstart, &slbitmap)) {
+ *page = pool->freelist[slindex].page;
+ *offset = pool->freelist[slindex].offset;
+ return slindex;
+ }
+
+ /*
+ * No best-fit found. Search a bit further in bitmap for a free block.
+ * Second level bitmap consists of series of 32-bit chunks. Search
+ * further in the chunk where we expected a best-fit, starting from
+ * index location found above.
+ */
+ slbitstart++;
+ slbitmap >>= slbitstart;
+
+ /* Skip this search if we were already at end of this bitmap chunk */
+ if ((slbitstart != BITS_PER_LONG) && slbitmap) {
+ slindex += __ffs(slbitmap) + 1;
+ *page = pool->freelist[slindex].page;
+ *offset = pool->freelist[slindex].offset;
+ return slindex;
+ }
+
+ /* Now do a full two-level bitmap search to find next nearest fit */
+ flindex = slindex / BITS_PER_LONG;
+
+ flbitmap = (pool->flbitmap) >> (flindex + 1);
+ if (!flbitmap)
+ return 0;
+
+ flindex += __ffs(flbitmap) + 1;
+ slbitmap = pool->slbitmap[flindex];
+ slindex = (flindex * BITS_PER_LONG) + __ffs(slbitmap);
+ *page = pool->freelist[slindex].page;
+ *offset = pool->freelist[slindex].offset;
+
+ return slindex;
+}
+
+/*
+ * Insert block at <page, offset> in freelist of given pool.
+ * freelist used depends on block size.
+ */
+static void insert_block(struct xv_pool *pool, struct page *page, u32 offset,
+ struct block_header *block)
+{
+ u32 flindex, slindex;
+ struct block_header *nextblock;
+
+ slindex = get_index_for_insert(block->size);
+ flindex = slindex / BITS_PER_LONG;
+
+ block->link.prev_page = NULL;
+ block->link.prev_offset = 0;
+ block->link.next_page = pool->freelist[slindex].page;
+ block->link.next_offset = pool->freelist[slindex].offset;
+ pool->freelist[slindex].page = page;
+ pool->freelist[slindex].offset = offset;
+
+ if (block->link.next_page) {
+ nextblock = get_ptr_atomic(block->link.next_page,
+ block->link.next_offset, KM_USER1);
+ nextblock->link.prev_page = page;
+ nextblock->link.prev_offset = offset;
+ put_ptr_atomic(nextblock, KM_USER1);
+ /* If there was a next page then the free bits are set. */
+ return;
+ }
+
+ __set_bit(slindex % BITS_PER_LONG, &pool->slbitmap[flindex]);
+ __set_bit(flindex, &pool->flbitmap);
+}
+
+/*
+ * Remove block from freelist. Index 'slindex' identifies the freelist.
+ */
+static void remove_block(struct xv_pool *pool, struct page *page, u32 offset,
+ struct block_header *block, u32 slindex)
+{
+ u32 flindex = slindex / BITS_PER_LONG;
+ struct block_header *tmpblock;
+
+ if (block->link.prev_page) {
+ tmpblock = get_ptr_atomic(block->link.prev_page,
+ block->link.prev_offset, KM_USER1);
+ tmpblock->link.next_page = block->link.next_page;
+ tmpblock->link.next_offset = block->link.next_offset;
+ put_ptr_atomic(tmpblock, KM_USER1);
+ }
+
+ if (block->link.next_page) {
+ tmpblock = get_ptr_atomic(block->link.next_page,
+ block->link.next_offset, KM_USER1);
+ tmpblock->link.prev_page = block->link.prev_page;
+ tmpblock->link.prev_offset = block->link.prev_offset;
+ put_ptr_atomic(tmpblock, KM_USER1);
+ }
+
+ /* Is this block is at the head of the freelist? */
+ if (pool->freelist[slindex].page == page
+ && pool->freelist[slindex].offset == offset) {
+
+ pool->freelist[slindex].page = block->link.next_page;
+ pool->freelist[slindex].offset = block->link.next_offset;
+
+ if (pool->freelist[slindex].page) {
+ struct block_header *tmpblock;
+ tmpblock = get_ptr_atomic(pool->freelist[slindex].page,
+ pool->freelist[slindex].offset,
+ KM_USER1);
+ tmpblock->link.prev_page = NULL;
+ tmpblock->link.prev_offset = 0;
+ put_ptr_atomic(tmpblock, KM_USER1);
+ } else {
+ /* This freelist bucket is empty */
+ __clear_bit(slindex % BITS_PER_LONG,
+ &pool->slbitmap[flindex]);
+ if (!pool->slbitmap[flindex])
+ __clear_bit(flindex, &pool->flbitmap);
+ }
+ }
+
+ block->link.prev_page = NULL;
+ block->link.prev_offset = 0;
+ block->link.next_page = NULL;
+ block->link.next_offset = 0;
+}
+
+/*
+ * Allocate a page and add it to freelist of given pool.
+ */
+static int grow_pool(struct xv_pool *pool, gfp_t flags)
+{
+ struct page *page;
+ struct block_header *block;
+
+ page = alloc_page(flags);
+ if (unlikely(!page))
+ return -ENOMEM;
+
+ stat_inc(&pool->total_pages);
+
+ spin_lock(&pool->lock);
+ block = get_ptr_atomic(page, 0, KM_USER0);
+
+ block->size = PAGE_SIZE - XV_ALIGN;
+ set_flag(block, BLOCK_FREE);
+ clear_flag(block, PREV_FREE);
+ set_blockprev(block, 0);
+
+ insert_block(pool, page, 0, block);
+
+ put_ptr_atomic(block, KM_USER0);
+ spin_unlock(&pool->lock);
+
+ return 0;
+}
+
+/*
+ * Create a memory pool. Allocates freelist, bitmaps and other
+ * per-pool metadata.
+ */
+struct xv_pool *xv_create_pool(void)
+{
+ u32 ovhd_size;
+ struct xv_pool *pool;
+
+ ovhd_size = roundup(sizeof(*pool), PAGE_SIZE);
+ pool = kzalloc(ovhd_size, GFP_KERNEL);
+ if (!pool)
+ return NULL;
+
+ spin_lock_init(&pool->lock);
+
+ return pool;
+}
+EXPORT_SYMBOL_GPL(xv_create_pool);
+
+void xv_destroy_pool(struct xv_pool *pool)
+{
+ kfree(pool);
+}
+EXPORT_SYMBOL_GPL(xv_destroy_pool);
+
+/**
+ * xv_malloc - Allocate block of given size from pool.
+ * @pool: pool to allocate from
+ * @size: size of block to allocate
+ * @page: page no. that holds the object
+ * @offset: location of object within page
+ *
+ * On success, <page, offset> identifies block allocated
+ * and 0 is returned. On failure, <page, offset> is set to
+ * 0 and -ENOMEM is returned.
+ *
+ * Allocation requests with size > XV_MAX_ALLOC_SIZE will fail.
+ */
+int xv_malloc(struct xv_pool *pool, u32 size, struct page **page,
+ u32 *offset, gfp_t flags)
+{
+ int error;
+ u32 index, tmpsize, origsize, tmpoffset;
+ struct block_header *block, *tmpblock;
+
+ *page = NULL;
+ *offset = 0;
+ origsize = size;
+
+ if (unlikely(!size || size > XV_MAX_ALLOC_SIZE))
+ return -ENOMEM;
+
+ size = ALIGN(size, XV_ALIGN);
+
+ spin_lock(&pool->lock);
+
+ index = find_block(pool, size, page, offset);
+
+ if (!*page) {
+ spin_unlock(&pool->lock);
+ if (flags & GFP_NOWAIT)
+ return -ENOMEM;
+ error = grow_pool(pool, flags);
+ if (unlikely(error))
+ return error;
+
+ spin_lock(&pool->lock);
+ index = find_block(pool, size, page, offset);
+ }
+
+ if (!*page) {
+ spin_unlock(&pool->lock);
+ return -ENOMEM;
+ }
+
+ block = get_ptr_atomic(*page, *offset, KM_USER0);
+
+ remove_block(pool, *page, *offset, block, index);
+
+ /* Split the block if required */
+ tmpoffset = *offset + size + XV_ALIGN;
+ tmpsize = block->size - size;
+ tmpblock = (struct block_header *)((char *)block + size + XV_ALIGN);
+ if (tmpsize) {
+ tmpblock->size = tmpsize - XV_ALIGN;
+ set_flag(tmpblock, BLOCK_FREE);
+ clear_flag(tmpblock, PREV_FREE);
+
+ set_blockprev(tmpblock, *offset);
+ if (tmpblock->size >= XV_MIN_ALLOC_SIZE)
+ insert_block(pool, *page, tmpoffset, tmpblock);
+
+ if (tmpoffset + XV_ALIGN + tmpblock->size != PAGE_SIZE) {
+ tmpblock = BLOCK_NEXT(tmpblock);
+ set_blockprev(tmpblock, tmpoffset);
+ }
+ } else {
+ /* This block is exact fit */
+ if (tmpoffset != PAGE_SIZE)
+ clear_flag(tmpblock, PREV_FREE);
+ }
+
+ block->size = origsize;
+ clear_flag(block, BLOCK_FREE);
+
+ put_ptr_atomic(block, KM_USER0);
+ spin_unlock(&pool->lock);
+
+ *offset += XV_ALIGN;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(xv_malloc);
+
+/*
+ * Free block identified with <page, offset>
+ */
+void xv_free(struct xv_pool *pool, struct page *page, u32 offset)
+{
+ void *page_start;
+ struct block_header *block, *tmpblock;
+
+ offset -= XV_ALIGN;
+
+ spin_lock(&pool->lock);
+
+ page_start = get_ptr_atomic(page, 0, KM_USER0);
+ block = (struct block_header *)((char *)page_start + offset);
+
+ /* Catch double free bugs */
+ BUG_ON(test_flag(block, BLOCK_FREE));
+
+ block->size = ALIGN(block->size, XV_ALIGN);
+
+ tmpblock = BLOCK_NEXT(block);
+ if (offset + block->size + XV_ALIGN == PAGE_SIZE)
+ tmpblock = NULL;
+
+ /* Merge next block if its free */
+ if (tmpblock && test_flag(tmpblock, BLOCK_FREE)) {
+ /*
+ * Blocks smaller than XV_MIN_ALLOC_SIZE
+ * are not inserted in any free list.
+ */
+ if (tmpblock->size >= XV_MIN_ALLOC_SIZE) {
+ remove_block(pool, page,
+ offset + block->size + XV_ALIGN, tmpblock,
+ get_index_for_insert(tmpblock->size));
+ }
+ block->size += tmpblock->size + XV_ALIGN;
+ }
+
+ /* Merge previous block if its free */
+ if (test_flag(block, PREV_FREE)) {
+ tmpblock = (struct block_header *)((char *)(page_start) +
+ get_blockprev(block));
+ offset = offset - tmpblock->size - XV_ALIGN;
+
+ if (tmpblock->size >= XV_MIN_ALLOC_SIZE)
+ remove_block(pool, page, offset, tmpblock,
+ get_index_for_insert(tmpblock->size));
+
+ tmpblock->size += block->size + XV_ALIGN;
+ block = tmpblock;
+ }
+
+ /* No used objects in this page. Free it. */
+ if (block->size == PAGE_SIZE - XV_ALIGN) {
+ put_ptr_atomic(page_start, KM_USER0);
+ spin_unlock(&pool->lock);
+
+ __free_page(page);
+ stat_dec(&pool->total_pages);
+ return;
+ }
+
+ set_flag(block, BLOCK_FREE);
+ if (block->size >= XV_MIN_ALLOC_SIZE)
+ insert_block(pool, page, offset, block);
+
+ if (offset + block->size + XV_ALIGN != PAGE_SIZE) {
+ tmpblock = BLOCK_NEXT(block);
+ set_flag(tmpblock, PREV_FREE);
+ set_blockprev(tmpblock, offset);
+ }
+
+ put_ptr_atomic(page_start, KM_USER0);
+ spin_unlock(&pool->lock);
+}
+EXPORT_SYMBOL_GPL(xv_free);
+
+u32 xv_get_object_size(void *obj)
+{
+ struct block_header *blk;
+
+ blk = (struct block_header *)((char *)(obj) - XV_ALIGN);
+ return blk->size;
+}
+EXPORT_SYMBOL_GPL(xv_get_object_size);
+
+/*
+ * Returns total memory used by allocator (userdata + metadata)
+ */
+u64 xv_get_total_size_bytes(struct xv_pool *pool)
+{
+ return pool->total_pages << PAGE_SHIFT;
+}
+EXPORT_SYMBOL_GPL(xv_get_total_size_bytes);
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