1 files changed, 0 insertions, 527 deletions
diff --git a/mm/zbud.c b/mm/zbud.c
deleted file mode 100644
index 9bb4710e3589..000000000000
--- a/mm/zbud.c
+++ /dev/null
@@ -1,527 +0,0 @@
-/*
- * zbud.c
- *
- * Copyright (C) 2013, Seth Jennings, IBM
- *
- * Concepts based on zcache internal zbud allocator by Dan Magenheimer.
- *
- * zbud is an special purpose allocator for storing compressed pages.  Contrary
- * to what its name may suggest, zbud is not a buddy allocator, but rather an
- * allocator that "buddies" two compressed pages together in a single memory
- * page.
- *
- * While this design limits storage density, it has simple and deterministic
- * reclaim properties that make it preferable to a higher density approach when
- * reclaim will be used.
- *
- * zbud works by storing compressed pages, or "zpages", together in pairs in a
- * single memory page called a "zbud page".  The first buddy is "left
- * justifed" at the beginning of the zbud page, and the last buddy is "right
- * justified" at the end of the zbud page.  The benefit is that if either
- * buddy is freed, the freed buddy space, coalesced with whatever slack space
- * that existed between the buddies, results in the largest possible free region
- * within the zbud page.
- *
- * zbud also provides an attractive lower bound on density. The ratio of zpages
- * to zbud pages can not be less than 1.  This ensures that zbud can never "do
- * harm" by using more pages to store zpages than the uncompressed zpages would
- * have used on their own.
- *
- * zbud pages are divided into "chunks".  The size of the chunks is fixed at
- * compile time and determined by NCHUNKS_ORDER below.  Dividing zbud pages
- * into chunks allows organizing unbuddied zbud pages into a manageable number
- * of unbuddied lists according to the number of free chunks available in the
- * zbud page.
- *
- * The zbud API differs from that of conventional allocators in that the
- * allocation function, zbud_alloc(), returns an opaque handle to the user,
- * not a dereferenceable pointer.  The user must map the handle using
- * zbud_map() in order to get a usable pointer by which to access the
- * allocation data and unmap the handle with zbud_unmap() when operations
- * on the allocation data are complete.
- */
-
-#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/zbud.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, and there
- * will be 64 freelists per pool.
- */
-#define NCHUNKS_ORDER	6
-
-#define CHUNK_SHIFT	(PAGE_SHIFT - NCHUNKS_ORDER)
-#define CHUNK_SIZE	(1 << CHUNK_SHIFT)
-#define NCHUNKS		(PAGE_SIZE >> CHUNK_SHIFT)
-#define ZHDR_SIZE_ALIGNED CHUNK_SIZE
-
-/**
- * struct zbud_pool - stores metadata for each zbud pool
- * @lock:	protects all pool fields and first|last_chunk fields of any
- *		zbud page in the pool
- * @unbuddied:	array of lists tracking zbud pages that only contain one buddy;
- *		the lists each zbud page is added to depends on the size of
- *		its free region.
- * @buddied:	list tracking the zbud pages that contain two buddies;
- *		these zbud pages are full
- * @lru:	list tracking the zbud pages in LRU order by most recently
- *		added buddy.
- * @pages_nr:	number of zbud 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 zbud pool.
- */
-struct zbud_pool {
-	spinlock_t lock;
-	struct list_head unbuddied[NCHUNKS];
-	struct list_head buddied;
-	struct list_head lru;
-	u64 pages_nr;
-	struct zbud_ops *ops;
-};
-
-/*
- * struct zbud_header - zbud page metadata occupying the first chunk of each
- *			zbud page.
- * @buddy:	links the zbud page into the unbuddied/buddied lists in the pool
- * @lru:	links the zbud page into the lru list in the pool
- * @first_chunks:	the size of the first buddy in chunks, 0 if free
- * @last_chunks:	the size of the last buddy in chunks, 0 if free
- */
-struct zbud_header {
-	struct list_head buddy;
-	struct list_head lru;
-	unsigned int first_chunks;
-	unsigned int last_chunks;
-	bool under_reclaim;
-};
-
-/*****************
- * Helpers
-*****************/
-/* Just to make the code easier to read */
-enum buddy {
-	FIRST,
-	LAST
-};
-
-/* Converts an allocation size in bytes to size in zbud chunks */
-static int size_to_chunks(int size)
-{
-	return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
-}
-
-#define for_each_unbuddied_list(_iter, _begin) \
-	for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
-
-/* Initializes the zbud header of a newly allocated zbud page */
-static struct zbud_header *init_zbud_page(struct page *page)
-{
-	struct zbud_header *zhdr = page_address(page);
-	zhdr->first_chunks = 0;
-	zhdr->last_chunks = 0;
-	INIT_LIST_HEAD(&zhdr->buddy);
-	INIT_LIST_HEAD(&zhdr->lru);
-	zhdr->under_reclaim = 0;
-	return zhdr;
-}
-
-/* Resets the struct page fields and frees the page */
-static void free_zbud_page(struct zbud_header *zhdr)
-{
-	__free_page(virt_to_page(zhdr));
-}
-
-/*
- * Encodes the handle of a particular buddy within a zbud page
- * Pool lock should be held as this function accesses first|last_chunks
- */
-static unsigned long encode_handle(struct zbud_header *zhdr, enum buddy bud)
-{
-	unsigned long handle;
-
-	/*
-	 * For now, the encoded handle is actually just the pointer to the data
-	 * but this might not always be the case.  A little information hiding.
-	 * Add CHUNK_SIZE to the handle if it is the first allocation to jump
-	 * over the zbud header in the first chunk.
-	 */
-	handle = (unsigned long)zhdr;
-	if (bud == FIRST)
-		/* skip over zbud header */
-		handle += ZHDR_SIZE_ALIGNED;
-	else /* bud == LAST */
-		handle += PAGE_SIZE - (zhdr->last_chunks  << CHUNK_SHIFT);
-	return handle;
-}
-
-/* Returns the zbud page where a given handle is stored */
-static struct zbud_header *handle_to_zbud_header(unsigned long handle)
-{
-	return (struct zbud_header *)(handle & PAGE_MASK);
-}
-
-/* Returns the number of free chunks in a zbud page */
-static int num_free_chunks(struct zbud_header *zhdr)
-{
-	/*
-	 * Rather than branch for different situations, just use the fact that
-	 * free buddies have a length of zero to simplify everything. -1 at the
-	 * end for the zbud header.
-	 */
-	return NCHUNKS - zhdr->first_chunks - zhdr->last_chunks - 1;
-}
-
-/*****************
- * API Functions
-*****************/
-/**
- * zbud_create_pool() - create a new zbud pool
- * @gfp:	gfp flags when allocating the zbud pool structure
- * @ops:	user-defined operations for the zbud pool
- *
- * Return: pointer to the new zbud pool or NULL if the metadata allocation
- * failed.
- */
-struct zbud_pool *zbud_create_pool(gfp_t gfp, struct zbud_ops *ops)
-{
-	struct zbud_pool *pool;
-	int i;
-
-	pool = kmalloc(sizeof(struct zbud_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;
-}
-
-/**
- * zbud_destroy_pool() - destroys an existing zbud pool
- * @pool:	the zbud pool to be destroyed
- *
- * The pool should be emptied before this function is called.
- */
-void zbud_destroy_pool(struct zbud_pool *pool)
-{
-	kfree(pool);
-}
-
-/**
- * zbud_alloc() - allocates a region of a given size
- * @pool:	zbud 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 zbud pool pages.
- *
- * Return: 0 if success and handle is set, otherwise -EINVAL is the size or
- * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
- * a new page.
- */
-int zbud_alloc(struct zbud_pool *pool, int size, gfp_t gfp,
-			unsigned long *handle)
-{
-	int chunks, i, freechunks;
-	struct zbud_header *zhdr = NULL;
-	enum buddy bud;
-	struct page *page;
-
-	if (size <= 0 || gfp & __GFP_HIGHMEM)
-		return -EINVAL;
-	if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED)
-		return -ENOSPC;
-	chunks = size_to_chunks(size);
-	spin_lock(&pool->lock);
-
-	/* First, try to find an unbuddied zbud page. */
-	zhdr = NULL;
-	for_each_unbuddied_list(i, chunks) {
-		if (!list_empty(&pool->unbuddied[i])) {
-			zhdr = list_first_entry(&pool->unbuddied[i],
-					struct zbud_header, buddy);
-			list_del(&zhdr->buddy);
-			if (zhdr->first_chunks == 0)
-				bud = FIRST;
-			else
-				bud = LAST;
-			goto found;
-		}
-	}
-
-	/* Couldn't find unbuddied zbud page, create new one */
-	spin_unlock(&pool->lock);
-	page = alloc_page(gfp);
-	if (!page)
-		return -ENOMEM;
-	spin_lock(&pool->lock);
-	pool->pages_nr++;
-	zhdr = init_zbud_page(page);
-	bud = FIRST;
-
-found:
-	if (bud == FIRST)
-		zhdr->first_chunks = chunks;
-	else
-		zhdr->last_chunks = chunks;
-
-	if (zhdr->first_chunks == 0 || zhdr->last_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);
-	}
-
-	/* Add/move zbud page to beginning of LRU */
-	if (!list_empty(&zhdr->lru))
-		list_del(&zhdr->lru);
-	list_add(&zhdr->lru, &pool->lru);
-
-	*handle = encode_handle(zhdr, bud);
-	spin_unlock(&pool->lock);
-
-	return 0;
-}
-
-/**
- * zbud_free() - frees the allocation associated with the given handle
- * @pool:	pool in which the allocation resided
- * @handle:	handle associated with the allocation returned by zbud_alloc()
- *
- * In the case that the zbud 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 zbud_reclaim_page() below).
- */
-void zbud_free(struct zbud_pool *pool, unsigned long handle)
-{
-	struct zbud_header *zhdr;
-	int freechunks;
-
-	spin_lock(&pool->lock);
-	zhdr = handle_to_zbud_header(handle);
-
-	/* If first buddy, handle will be page aligned */
-	if ((handle - ZHDR_SIZE_ALIGNED) & ~PAGE_MASK)
-		zhdr->last_chunks = 0;
-	else
-		zhdr->first_chunks = 0;
-
-	if (zhdr->under_reclaim) {
-		/* zbud page is under reclaim, reclaim will free */
-		spin_unlock(&pool->lock);
-		return;
-	}
-
-	/* Remove from existing buddy list */
-	list_del(&zhdr->buddy);
-
-	if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
-		/* zbud page is empty, free */
-		list_del(&zhdr->lru);
-		free_zbud_page(zhdr);
-		pool->pages_nr--;
-	} else {
-		/* Add to unbuddied list */
-		freechunks = num_free_chunks(zhdr);
-		list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
-	}
-
-	spin_unlock(&pool->lock);
-}
-
-#define list_tail_entry(ptr, type, member) \
-	list_entry((ptr)->prev, type, member)
-
-/**
- * zbud_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
- *
- * zbud reclaim is different from normal system reclaim in that the reclaim is
- * done from the bottom, up.  This is because only the bottom layer, zbud, has
- * information on how the allocations are organized within each zbud page. This
- * has the potential to create interesting locking situations between zbud and
- * the user, however.
- *
- * To avoid these, this is how zbud_reclaim_page() should be called:
-
- * The user detects a page should be reclaimed and calls zbud_reclaim_page().
- * zbud_reclaim_page() will remove a zbud 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. zbud_reclaim_page() will add the zbud page back to the
- * appropriate list and try the next zbud 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 zbud_free() on the handle. zbud_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 zbud page are successfully evicted, then the
- * zbud 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.
- */
-int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)
-{
-	int i, ret, freechunks;
-	struct zbud_header *zhdr;
-	unsigned long first_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++) {
-		zhdr = list_tail_entry(&pool->lru, struct zbud_header, lru);
-		list_del(&zhdr->lru);
-		list_del(&zhdr->buddy);
-		/* Protect zbud page against free */
-		zhdr->under_reclaim = true;
-		/*
-		 * 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;
-		if (zhdr->first_chunks)
-			first_handle = encode_handle(zhdr, FIRST);
-		if (zhdr->last_chunks)
-			last_handle = encode_handle(zhdr, LAST);
-		spin_unlock(&pool->lock);
-
-		/* Issue the eviction callback(s) */
-		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);
-		zhdr->under_reclaim = false;
-		if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
-			/*
-			 * Both buddies are now free, free the zbud page and
-			 * return success.
-			 */
-			free_zbud_page(zhdr);
-			pool->pages_nr--;
-			spin_unlock(&pool->lock);
-			return 0;
-		} else if (zhdr->first_chunks == 0 ||
-				zhdr->last_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);
-		}
-
-		/* add to beginning of LRU */
-		list_add(&zhdr->lru, &pool->lru);
-	}
-	spin_unlock(&pool->lock);
-	return -EAGAIN;
-}
-
-/**
- * zbud_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
- *
- * While trivial for zbud, the mapping functions for others allocators
- * implementing this allocation API could have more complex information encoded
- * in the handle and could create temporary mappings to make the data
- * accessible to the user.
- *
- * Returns: a pointer to the mapped allocation
- */
-void *zbud_map(struct zbud_pool *pool, unsigned long handle)
-{
-	return (void *)(handle);
-}
-
-/**
- * zbud_unmap() - maps the allocation associated with the given handle
- * @pool:	pool in which the allocation resides
- * @handle:	handle associated with the allocation to be unmapped
- */
-void zbud_unmap(struct zbud_pool *pool, unsigned long handle)
-{
-}
-
-/**
- * zbud_get_pool_size() - gets the zbud 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.
- */
-u64 zbud_get_pool_size(struct zbud_pool *pool)
-{
-	return pool->pages_nr;
-}
-
-static int __init init_zbud(void)
-{
-	/* Make sure the zbud header will fit in one chunk */
-	BUILD_BUG_ON(sizeof(struct zbud_header) > ZHDR_SIZE_ALIGNED);
-	pr_info("loaded\n");
-	return 0;
-}
-
-static void __exit exit_zbud(void)
-{
-	pr_info("unloaded\n");
-}
-
-module_init(init_zbud);
-module_exit(exit_zbud);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Seth Jennings <sjenning@linux.vnet.ibm.com>");
-MODULE_DESCRIPTION("Buddy Allocator for Compressed Pages");