Linux-libre 4.7.1-gnupck-4.7.1-gnu

1 files changed, 796 insertions, 0 deletions

diff --git a/mm/z3fold.c b/mm/z3fold.c
new file mode 100644
index 000000000..8f9e89ca1
--- /dev/null
+++ b/mm/z3fold.c
@@ -0,0 +1,796 @@
+/*
+ * z3fold.c
+ *
+ * Author: Vitaly Wool <vitaly.wool@konsulko.com>
+ * Copyright (C) 2016, Sony Mobile Communications Inc.
+ *
+ * This implementation is based on zbud written by Seth Jennings.
+ *
+ * z3fold is an special purpose allocator for storing compressed pages. It
+ * can store up to three compressed pages per page which improves the
+ * compression ratio of zbud while retaining its main concepts (e. g. always
+ * storing an integral number of objects per page) and simplicity.
+ * It still has simple and deterministic reclaim properties that make it
+ * preferable to a higher density approach (with no requirement on integral
+ * number of object per page) when reclaim is used.
+ *
+ * As in zbud, pages are divided into "chunks".  The size of the chunks is
+ * fixed at compile time and is determined by NCHUNKS_ORDER below.
+ *
+ * z3fold doesn't export any API and is meant to be used via zpool API.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/atomic.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/preempt.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/zpool.h>
+
+/*****************
+ * Structures
+*****************/
+/*
+ * NCHUNKS_ORDER determines the internal allocation granularity, effectively
+ * adjusting internal fragmentation.  It also determines the number of
+ * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
+ * allocation granularity will be in chunks of size PAGE_SIZE/64. As one chunk
+ * in allocated page is occupied by z3fold header, NCHUNKS will be calculated
+ * to 63 which shows the max number of free chunks in z3fold page, also there
+ * will be 63 freelists per pool.
+ */
+#define NCHUNKS_ORDER	6
+
+#define CHUNK_SHIFT	(PAGE_SHIFT - NCHUNKS_ORDER)
+#define CHUNK_SIZE	(1 << CHUNK_SHIFT)
+#define ZHDR_SIZE_ALIGNED CHUNK_SIZE
+#define NCHUNKS		((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
+
+#define BUDDY_MASK	((1 << NCHUNKS_ORDER) - 1)
+
+struct z3fold_pool;
+struct z3fold_ops {
+	int (*evict)(struct z3fold_pool *pool, unsigned long handle);
+};
+
+/**
+ * struct z3fold_pool - stores metadata for each z3fold pool
+ * @lock:	protects all pool fields and first|last_chunk fields of any
+ *		z3fold page in the pool
+ * @unbuddied:	array of lists tracking z3fold pages that contain 2- buddies;
+ *		the lists each z3fold page is added to depends on the size of
+ *		its free region.
+ * @buddied:	list tracking the z3fold pages that contain 3 buddies;
+ *		these z3fold pages are full
+ * @lru:	list tracking the z3fold pages in LRU order by most recently
+ *		added buddy.
+ * @pages_nr:	number of z3fold pages in the pool.
+ * @ops:	pointer to a structure of user defined operations specified at
+ *		pool creation time.
+ *
+ * This structure is allocated at pool creation time and maintains metadata
+ * pertaining to a particular z3fold pool.
+ */
+struct z3fold_pool {
+	spinlock_t lock;
+	struct list_head unbuddied[NCHUNKS];
+	struct list_head buddied;
+	struct list_head lru;
+	u64 pages_nr;
+	const struct z3fold_ops *ops;
+	struct zpool *zpool;
+	const struct zpool_ops *zpool_ops;
+};
+
+enum buddy {
+	HEADLESS = 0,
+	FIRST,
+	MIDDLE,
+	LAST,
+	BUDDIES_MAX
+};
+
+/*
+ * struct z3fold_header - z3fold page metadata occupying the first chunk of each
+ *			z3fold page, except for HEADLESS pages
+ * @buddy:	links the z3fold page into the relevant list in the pool
+ * @first_chunks:	the size of the first buddy in chunks, 0 if free
+ * @middle_chunks:	the size of the middle buddy in chunks, 0 if free
+ * @last_chunks:	the size of the last buddy in chunks, 0 if free
+ * @first_num:		the starting number (for the first handle)
+ */
+struct z3fold_header {
+	struct list_head buddy;
+	unsigned short first_chunks;
+	unsigned short middle_chunks;
+	unsigned short last_chunks;
+	unsigned short start_middle;
+	unsigned short first_num:NCHUNKS_ORDER;
+};
+
+/*
+ * Internal z3fold page flags
+ */
+enum z3fold_page_flags {
+	UNDER_RECLAIM = 0,
+	PAGE_HEADLESS,
+	MIDDLE_CHUNK_MAPPED,
+};
+
+/*****************
+ * Helpers
+*****************/
+
+/* Converts an allocation size in bytes to size in z3fold chunks */
+static int size_to_chunks(size_t size)
+{
+	return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
+}
+
+#define for_each_unbuddied_list(_iter, _begin) \
+	for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
+
+/* Initializes the z3fold header of a newly allocated z3fold page */
+static struct z3fold_header *init_z3fold_page(struct page *page)
+{
+	struct z3fold_header *zhdr = page_address(page);
+
+	INIT_LIST_HEAD(&page->lru);
+	clear_bit(UNDER_RECLAIM, &page->private);
+	clear_bit(PAGE_HEADLESS, &page->private);
+	clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
+
+	zhdr->first_chunks = 0;
+	zhdr->middle_chunks = 0;
+	zhdr->last_chunks = 0;
+	zhdr->first_num = 0;
+	zhdr->start_middle = 0;
+	INIT_LIST_HEAD(&zhdr->buddy);
+	return zhdr;
+}
+
+/* Resets the struct page fields and frees the page */
+static void free_z3fold_page(struct z3fold_header *zhdr)
+{
+	__free_page(virt_to_page(zhdr));
+}
+
+/*
+ * Encodes the handle of a particular buddy within a z3fold page
+ * Pool lock should be held as this function accesses first_num
+ */
+static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
+{
+	unsigned long handle;
+
+	handle = (unsigned long)zhdr;
+	if (bud != HEADLESS)
+		handle += (bud + zhdr->first_num) & BUDDY_MASK;
+	return handle;
+}
+
+/* Returns the z3fold page where a given handle is stored */
+static struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
+{
+	return (struct z3fold_header *)(handle & PAGE_MASK);
+}
+
+/* Returns buddy number */
+static enum buddy handle_to_buddy(unsigned long handle)
+{
+	struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
+	return (handle - zhdr->first_num) & BUDDY_MASK;
+}
+
+/*
+ * Returns the number of free chunks in a z3fold page.
+ * NB: can't be used with HEADLESS pages.
+ */
+static int num_free_chunks(struct z3fold_header *zhdr)
+{
+	int nfree;
+	/*
+	 * If there is a middle object, pick up the bigger free space
+	 * either before or after it. Otherwise just subtract the number
+	 * of chunks occupied by the first and the last objects.
+	 */
+	if (zhdr->middle_chunks != 0) {
+		int nfree_before = zhdr->first_chunks ?
+			0 : zhdr->start_middle - 1;
+		int nfree_after = zhdr->last_chunks ?
+			0 : NCHUNKS - zhdr->start_middle - zhdr->middle_chunks;
+		nfree = max(nfree_before, nfree_after);
+	} else
+		nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
+	return nfree;
+}
+
+/*****************
+ * API Functions
+*****************/
+/**
+ * z3fold_create_pool() - create a new z3fold pool
+ * @gfp:	gfp flags when allocating the z3fold pool structure
+ * @ops:	user-defined operations for the z3fold pool
+ *
+ * Return: pointer to the new z3fold pool or NULL if the metadata allocation
+ * failed.
+ */
+static struct z3fold_pool *z3fold_create_pool(gfp_t gfp,
+		const struct z3fold_ops *ops)
+{
+	struct z3fold_pool *pool;
+	int i;
+
+	pool = kzalloc(sizeof(struct z3fold_pool), gfp);
+	if (!pool)
+		return NULL;
+	spin_lock_init(&pool->lock);
+	for_each_unbuddied_list(i, 0)
+		INIT_LIST_HEAD(&pool->unbuddied[i]);
+	INIT_LIST_HEAD(&pool->buddied);
+	INIT_LIST_HEAD(&pool->lru);
+	pool->pages_nr = 0;
+	pool->ops = ops;
+	return pool;
+}
+
+/**
+ * z3fold_destroy_pool() - destroys an existing z3fold pool
+ * @pool:	the z3fold pool to be destroyed
+ *
+ * The pool should be emptied before this function is called.
+ */
+static void z3fold_destroy_pool(struct z3fold_pool *pool)
+{
+	kfree(pool);
+}
+
+/* Has to be called with lock held */
+static int z3fold_compact_page(struct z3fold_header *zhdr)
+{
+	struct page *page = virt_to_page(zhdr);
+	void *beg = zhdr;
+
+
+	if (!test_bit(MIDDLE_CHUNK_MAPPED, &page->private) &&
+	    zhdr->middle_chunks != 0 &&
+	    zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
+		memmove(beg + ZHDR_SIZE_ALIGNED,
+			beg + (zhdr->start_middle << CHUNK_SHIFT),
+			zhdr->middle_chunks << CHUNK_SHIFT);
+		zhdr->first_chunks = zhdr->middle_chunks;
+		zhdr->middle_chunks = 0;
+		zhdr->start_middle = 0;
+		zhdr->first_num++;
+		return 1;
+	}
+	return 0;
+}
+
+/**
+ * z3fold_alloc() - allocates a region of a given size
+ * @pool:	z3fold pool from which to allocate
+ * @size:	size in bytes of the desired allocation
+ * @gfp:	gfp flags used if the pool needs to grow
+ * @handle:	handle of the new allocation
+ *
+ * This function will attempt to find a free region in the pool large enough to
+ * satisfy the allocation request.  A search of the unbuddied lists is
+ * performed first. If no suitable free region is found, then a new page is
+ * allocated and added to the pool to satisfy the request.
+ *
+ * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
+ * as z3fold pool pages.
+ *
+ * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
+ * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
+ * a new page.
+ */
+static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
+			unsigned long *handle)
+{
+	int chunks = 0, i, freechunks;
+	struct z3fold_header *zhdr = NULL;
+	enum buddy bud;
+	struct page *page;
+
+	if (!size || (gfp & __GFP_HIGHMEM))
+		return -EINVAL;
+
+	if (size > PAGE_SIZE)
+		return -ENOSPC;
+
+	if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
+		bud = HEADLESS;
+	else {
+		chunks = size_to_chunks(size);
+		spin_lock(&pool->lock);
+
+		/* First, try to find an unbuddied z3fold page. */
+		zhdr = NULL;
+		for_each_unbuddied_list(i, chunks) {
+			if (!list_empty(&pool->unbuddied[i])) {
+				zhdr = list_first_entry(&pool->unbuddied[i],
+						struct z3fold_header, buddy);
+				page = virt_to_page(zhdr);
+				if (zhdr->first_chunks == 0) {
+					if (zhdr->middle_chunks != 0 &&
+					    chunks >= zhdr->start_middle)
+						bud = LAST;
+					else
+						bud = FIRST;
+				} else if (zhdr->last_chunks == 0)
+					bud = LAST;
+				else if (zhdr->middle_chunks == 0)
+					bud = MIDDLE;
+				else {
+					pr_err("No free chunks in unbuddied\n");
+					WARN_ON(1);
+					continue;
+				}
+				list_del(&zhdr->buddy);
+				goto found;
+			}
+		}
+		bud = FIRST;
+		spin_unlock(&pool->lock);
+	}
+
+	/* Couldn't find unbuddied z3fold page, create new one */
+	page = alloc_page(gfp);
+	if (!page)
+		return -ENOMEM;
+	spin_lock(&pool->lock);
+	pool->pages_nr++;
+	zhdr = init_z3fold_page(page);
+
+	if (bud == HEADLESS) {
+		set_bit(PAGE_HEADLESS, &page->private);
+		goto headless;
+	}
+
+found:
+	if (bud == FIRST)
+		zhdr->first_chunks = chunks;
+	else if (bud == LAST)
+		zhdr->last_chunks = chunks;
+	else {
+		zhdr->middle_chunks = chunks;
+		zhdr->start_middle = zhdr->first_chunks + 1;
+	}
+
+	if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
+			zhdr->middle_chunks == 0) {
+		/* Add to unbuddied list */
+		freechunks = num_free_chunks(zhdr);
+		list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
+	} else {
+		/* Add to buddied list */
+		list_add(&zhdr->buddy, &pool->buddied);
+	}
+
+headless:
+	/* Add/move z3fold page to beginning of LRU */
+	if (!list_empty(&page->lru))
+		list_del(&page->lru);
+
+	list_add(&page->lru, &pool->lru);
+
+	*handle = encode_handle(zhdr, bud);
+	spin_unlock(&pool->lock);
+
+	return 0;
+}
+
+/**
+ * z3fold_free() - frees the allocation associated with the given handle
+ * @pool:	pool in which the allocation resided
+ * @handle:	handle associated with the allocation returned by z3fold_alloc()
+ *
+ * In the case that the z3fold page in which the allocation resides is under
+ * reclaim, as indicated by the PG_reclaim flag being set, this function
+ * only sets the first|last_chunks to 0.  The page is actually freed
+ * once both buddies are evicted (see z3fold_reclaim_page() below).
+ */
+static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
+{
+	struct z3fold_header *zhdr;
+	int freechunks;
+	struct page *page;
+	enum buddy bud;
+
+	spin_lock(&pool->lock);
+	zhdr = handle_to_z3fold_header(handle);
+	page = virt_to_page(zhdr);
+
+	if (test_bit(PAGE_HEADLESS, &page->private)) {
+		/* HEADLESS page stored */
+		bud = HEADLESS;
+	} else {
+		bud = handle_to_buddy(handle);
+
+		switch (bud) {
+		case FIRST:
+			zhdr->first_chunks = 0;
+			break;
+		case MIDDLE:
+			zhdr->middle_chunks = 0;
+			zhdr->start_middle = 0;
+			break;
+		case LAST:
+			zhdr->last_chunks = 0;
+			break;
+		default:
+			pr_err("%s: unknown bud %d\n", __func__, bud);
+			WARN_ON(1);
+			spin_unlock(&pool->lock);
+			return;
+		}
+	}
+
+	if (test_bit(UNDER_RECLAIM, &page->private)) {
+		/* z3fold page is under reclaim, reclaim will free */
+		spin_unlock(&pool->lock);
+		return;
+	}
+
+	if (bud != HEADLESS) {
+		/* Remove from existing buddy list */
+		list_del(&zhdr->buddy);
+	}
+
+	if (bud == HEADLESS ||
+	    (zhdr->first_chunks == 0 && zhdr->middle_chunks == 0 &&
+			zhdr->last_chunks == 0)) {
+		/* z3fold page is empty, free */
+		list_del(&page->lru);
+		clear_bit(PAGE_HEADLESS, &page->private);
+		free_z3fold_page(zhdr);
+		pool->pages_nr--;
+	} else {
+		z3fold_compact_page(zhdr);
+		/* Add to the unbuddied list */
+		freechunks = num_free_chunks(zhdr);
+		list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
+	}
+
+	spin_unlock(&pool->lock);
+}
+
+/**
+ * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
+ * @pool:	pool from which a page will attempt to be evicted
+ * @retires:	number of pages on the LRU list for which eviction will
+ *		be attempted before failing
+ *
+ * z3fold reclaim is different from normal system reclaim in that it is done
+ * from the bottom, up. This is because only the bottom layer, z3fold, has
+ * information on how the allocations are organized within each z3fold page.
+ * This has the potential to create interesting locking situations between
+ * z3fold and the user, however.
+ *
+ * To avoid these, this is how z3fold_reclaim_page() should be called:
+
+ * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
+ * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
+ * call the user-defined eviction handler with the pool and handle as
+ * arguments.
+ *
+ * If the handle can not be evicted, the eviction handler should return
+ * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
+ * appropriate list and try the next z3fold page on the LRU up to
+ * a user defined number of retries.
+ *
+ * If the handle is successfully evicted, the eviction handler should
+ * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
+ * contains logic to delay freeing the page if the page is under reclaim,
+ * as indicated by the setting of the PG_reclaim flag on the underlying page.
+ *
+ * If all buddies in the z3fold page are successfully evicted, then the
+ * z3fold page can be freed.
+ *
+ * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
+ * no pages to evict or an eviction handler is not registered, -EAGAIN if
+ * the retry limit was hit.
+ */
+static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
+{
+	int i, ret = 0, freechunks;
+	struct z3fold_header *zhdr;
+	struct page *page;
+	unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
+
+	spin_lock(&pool->lock);
+	if (!pool->ops || !pool->ops->evict || list_empty(&pool->lru) ||
+			retries == 0) {
+		spin_unlock(&pool->lock);
+		return -EINVAL;
+	}
+	for (i = 0; i < retries; i++) {
+		page = list_last_entry(&pool->lru, struct page, lru);
+		list_del(&page->lru);
+
+		/* Protect z3fold page against free */
+		set_bit(UNDER_RECLAIM, &page->private);
+		zhdr = page_address(page);
+		if (!test_bit(PAGE_HEADLESS, &page->private)) {
+			list_del(&zhdr->buddy);
+			/*
+			 * We need encode the handles before unlocking, since
+			 * we can race with free that will set
+			 * (first|last)_chunks to 0
+			 */
+			first_handle = 0;
+			last_handle = 0;
+			middle_handle = 0;
+			if (zhdr->first_chunks)
+				first_handle = encode_handle(zhdr, FIRST);
+			if (zhdr->middle_chunks)
+				middle_handle = encode_handle(zhdr, MIDDLE);
+			if (zhdr->last_chunks)
+				last_handle = encode_handle(zhdr, LAST);
+		} else {
+			first_handle = encode_handle(zhdr, HEADLESS);
+			last_handle = middle_handle = 0;
+		}
+
+		spin_unlock(&pool->lock);
+
+		/* Issue the eviction callback(s) */
+		if (middle_handle) {
+			ret = pool->ops->evict(pool, middle_handle);
+			if (ret)
+				goto next;
+		}
+		if (first_handle) {
+			ret = pool->ops->evict(pool, first_handle);
+			if (ret)
+				goto next;
+		}
+		if (last_handle) {
+			ret = pool->ops->evict(pool, last_handle);
+			if (ret)
+				goto next;
+		}
+next:
+		spin_lock(&pool->lock);
+		clear_bit(UNDER_RECLAIM, &page->private);
+		if ((test_bit(PAGE_HEADLESS, &page->private) && ret == 0) ||
+		    (zhdr->first_chunks == 0 && zhdr->last_chunks == 0 &&
+		     zhdr->middle_chunks == 0)) {
+			/*
+			 * All buddies are now free, free the z3fold page and
+			 * return success.
+			 */
+			clear_bit(PAGE_HEADLESS, &page->private);
+			free_z3fold_page(zhdr);
+			pool->pages_nr--;
+			spin_unlock(&pool->lock);
+			return 0;
+		}  else if (!test_bit(PAGE_HEADLESS, &page->private)) {
+			if (zhdr->first_chunks != 0 &&
+			    zhdr->last_chunks != 0 &&
+			    zhdr->middle_chunks != 0) {
+				/* Full, add to buddied list */
+				list_add(&zhdr->buddy, &pool->buddied);
+			} else {
+				z3fold_compact_page(zhdr);
+				/* add to unbuddied list */
+				freechunks = num_free_chunks(zhdr);
+				list_add(&zhdr->buddy,
+					 &pool->unbuddied[freechunks]);
+			}
+		}
+
+		/* add to beginning of LRU */
+		list_add(&page->lru, &pool->lru);
+	}
+	spin_unlock(&pool->lock);
+	return -EAGAIN;
+}
+
+/**
+ * z3fold_map() - maps the allocation associated with the given handle
+ * @pool:	pool in which the allocation resides
+ * @handle:	handle associated with the allocation to be mapped
+ *
+ * Extracts the buddy number from handle and constructs the pointer to the
+ * correct starting chunk within the page.
+ *
+ * Returns: a pointer to the mapped allocation
+ */
+static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
+{
+	struct z3fold_header *zhdr;
+	struct page *page;
+	void *addr;
+	enum buddy buddy;
+
+	spin_lock(&pool->lock);
+	zhdr = handle_to_z3fold_header(handle);
+	addr = zhdr;
+	page = virt_to_page(zhdr);
+
+	if (test_bit(PAGE_HEADLESS, &page->private))
+		goto out;
+
+	buddy = handle_to_buddy(handle);
+	switch (buddy) {
+	case FIRST:
+		addr += ZHDR_SIZE_ALIGNED;
+		break;
+	case MIDDLE:
+		addr += zhdr->start_middle << CHUNK_SHIFT;
+		set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
+		break;
+	case LAST:
+		addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
+		break;
+	default:
+		pr_err("unknown buddy id %d\n", buddy);
+		WARN_ON(1);
+		addr = NULL;
+		break;
+	}
+out:
+	spin_unlock(&pool->lock);
+	return addr;
+}
+
+/**
+ * z3fold_unmap() - unmaps the allocation associated with the given handle
+ * @pool:	pool in which the allocation resides
+ * @handle:	handle associated with the allocation to be unmapped
+ */
+static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
+{
+	struct z3fold_header *zhdr;
+	struct page *page;
+	enum buddy buddy;
+
+	spin_lock(&pool->lock);
+	zhdr = handle_to_z3fold_header(handle);
+	page = virt_to_page(zhdr);
+
+	if (test_bit(PAGE_HEADLESS, &page->private)) {
+		spin_unlock(&pool->lock);
+		return;
+	}
+
+	buddy = handle_to_buddy(handle);
+	if (buddy == MIDDLE)
+		clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
+	spin_unlock(&pool->lock);
+}
+
+/**
+ * z3fold_get_pool_size() - gets the z3fold pool size in pages
+ * @pool:	pool whose size is being queried
+ *
+ * Returns: size in pages of the given pool.  The pool lock need not be
+ * taken to access pages_nr.
+ */
+static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
+{
+	return pool->pages_nr;
+}
+
+/*****************
+ * zpool
+ ****************/
+
+static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
+{
+	if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
+		return pool->zpool_ops->evict(pool->zpool, handle);
+	else
+		return -ENOENT;
+}
+
+static const struct z3fold_ops z3fold_zpool_ops = {
+	.evict =	z3fold_zpool_evict
+};
+
+static void *z3fold_zpool_create(const char *name, gfp_t gfp,
+			       const struct zpool_ops *zpool_ops,
+			       struct zpool *zpool)
+{
+	struct z3fold_pool *pool;
+
+	pool = z3fold_create_pool(gfp, zpool_ops ? &z3fold_zpool_ops : NULL);
+	if (pool) {
+		pool->zpool = zpool;
+		pool->zpool_ops = zpool_ops;
+	}
+	return pool;
+}
+
+static void z3fold_zpool_destroy(void *pool)
+{
+	z3fold_destroy_pool(pool);
+}
+
+static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
+			unsigned long *handle)
+{
+	return z3fold_alloc(pool, size, gfp, handle);
+}
+static void z3fold_zpool_free(void *pool, unsigned long handle)
+{
+	z3fold_free(pool, handle);
+}
+
+static int z3fold_zpool_shrink(void *pool, unsigned int pages,
+			unsigned int *reclaimed)
+{
+	unsigned int total = 0;
+	int ret = -EINVAL;
+
+	while (total < pages) {
+		ret = z3fold_reclaim_page(pool, 8);
+		if (ret < 0)
+			break;
+		total++;
+	}
+
+	if (reclaimed)
+		*reclaimed = total;
+
+	return ret;
+}
+
+static void *z3fold_zpool_map(void *pool, unsigned long handle,
+			enum zpool_mapmode mm)
+{
+	return z3fold_map(pool, handle);
+}
+static void z3fold_zpool_unmap(void *pool, unsigned long handle)
+{
+	z3fold_unmap(pool, handle);
+}
+
+static u64 z3fold_zpool_total_size(void *pool)
+{
+	return z3fold_get_pool_size(pool) * PAGE_SIZE;
+}
+
+static struct zpool_driver z3fold_zpool_driver = {
+	.type =		"z3fold",
+	.owner =	THIS_MODULE,
+	.create =	z3fold_zpool_create,
+	.destroy =	z3fold_zpool_destroy,
+	.malloc =	z3fold_zpool_malloc,
+	.free =		z3fold_zpool_free,
+	.shrink =	z3fold_zpool_shrink,
+	.map =		z3fold_zpool_map,
+	.unmap =	z3fold_zpool_unmap,
+	.total_size =	z3fold_zpool_total_size,
+};
+
+MODULE_ALIAS("zpool-z3fold");
+
+static int __init init_z3fold(void)
+{
+	/* Make sure the z3fold header will fit in one chunk */
+	BUILD_BUG_ON(sizeof(struct z3fold_header) > ZHDR_SIZE_ALIGNED);
+	zpool_register_driver(&z3fold_zpool_driver);
+
+	return 0;
+}
+
+static void __exit exit_z3fold(void)
+{
+	zpool_unregister_driver(&z3fold_zpool_driver);
+}
+
+module_init(init_z3fold);
+module_exit(exit_z3fold);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
+MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");