v4.19.13 snapshot.
diff --git a/mm/z3fold.c b/mm/z3fold.c
new file mode 100644
index 0000000..aee9b0b
--- /dev/null
+++ b/mm/z3fold.c
@@ -0,0 +1,1153 @@
+/*
+ * 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/sched.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
+#include <linux/workqueue.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/zpool.h>
+
+/*****************
+ * Structures
+*****************/
+struct z3fold_pool;
+struct z3fold_ops {
+ int (*evict)(struct z3fold_pool *pool, unsigned long handle);
+};
+
+enum buddy {
+ HEADLESS = 0,
+ FIRST,
+ MIDDLE,
+ LAST,
+ BUDDIES_MAX
+};
+
+/*
+ * struct z3fold_header - z3fold page metadata occupying first chunks of each
+ * z3fold page, except for HEADLESS pages
+ * @buddy: links the z3fold page into the relevant list in the
+ * pool
+ * @page_lock: per-page lock
+ * @refcount: reference count for the z3fold page
+ * @work: work_struct for page layout optimization
+ * @pool: pointer to the pool which this page belongs to
+ * @cpu: CPU which this page "belongs" to
+ * @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;
+ spinlock_t page_lock;
+ struct kref refcount;
+ struct work_struct work;
+ struct z3fold_pool *pool;
+ short cpu;
+ unsigned short first_chunks;
+ unsigned short middle_chunks;
+ unsigned short last_chunks;
+ unsigned short start_middle;
+ unsigned short first_num:2;
+};
+
+/*
+ * 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. Some chunks
+ * in the beginning of an allocated page are occupied by z3fold header, so
+ * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
+ * which shows the max number of free chunks in z3fold page, also there will
+ * be 63, or 62, respectively, freelists per pool.
+ */
+#define NCHUNKS_ORDER 6
+
+#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
+#define CHUNK_SIZE (1 << CHUNK_SHIFT)
+#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
+#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
+#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
+#define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
+
+#define BUDDY_MASK (0x3)
+#define BUDDY_SHIFT 2
+
+/**
+ * struct z3fold_pool - stores metadata for each z3fold pool
+ * @name: pool name
+ * @lock: protects pool unbuddied/lru lists
+ * @stale_lock: protects pool stale page list
+ * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
+ * buddies; the list each z3fold page is added to depends on
+ * the size of its free region.
+ * @lru: list tracking the z3fold pages in LRU order by most recently
+ * added buddy.
+ * @stale: list of pages marked for freeing
+ * @pages_nr: number of z3fold pages in the pool.
+ * @ops: pointer to a structure of user defined operations specified at
+ * pool creation time.
+ * @compact_wq: workqueue for page layout background optimization
+ * @release_wq: workqueue for safe page release
+ * @work: work_struct for safe page release
+ *
+ * This structure is allocated at pool creation time and maintains metadata
+ * pertaining to a particular z3fold pool.
+ */
+struct z3fold_pool {
+ const char *name;
+ spinlock_t lock;
+ spinlock_t stale_lock;
+ struct list_head *unbuddied;
+ struct list_head lru;
+ struct list_head stale;
+ atomic64_t pages_nr;
+ const struct z3fold_ops *ops;
+ struct zpool *zpool;
+ const struct zpool_ops *zpool_ops;
+ struct workqueue_struct *compact_wq;
+ struct workqueue_struct *release_wq;
+ struct work_struct work;
+};
+
+/*
+ * Internal z3fold page flags
+ */
+enum z3fold_page_flags {
+ PAGE_HEADLESS = 0,
+ MIDDLE_CHUNK_MAPPED,
+ NEEDS_COMPACTING,
+ PAGE_STALE,
+ PAGE_CLAIMED, /* by either reclaim or free */
+};
+
+/*****************
+ * 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)++)
+
+static void compact_page_work(struct work_struct *w);
+
+/* Initializes the z3fold header of a newly allocated z3fold page */
+static struct z3fold_header *init_z3fold_page(struct page *page,
+ struct z3fold_pool *pool)
+{
+ struct z3fold_header *zhdr = page_address(page);
+
+ INIT_LIST_HEAD(&page->lru);
+ clear_bit(PAGE_HEADLESS, &page->private);
+ clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
+ clear_bit(NEEDS_COMPACTING, &page->private);
+ clear_bit(PAGE_STALE, &page->private);
+ clear_bit(PAGE_CLAIMED, &page->private);
+
+ spin_lock_init(&zhdr->page_lock);
+ kref_init(&zhdr->refcount);
+ zhdr->first_chunks = 0;
+ zhdr->middle_chunks = 0;
+ zhdr->last_chunks = 0;
+ zhdr->first_num = 0;
+ zhdr->start_middle = 0;
+ zhdr->cpu = -1;
+ zhdr->pool = pool;
+ INIT_LIST_HEAD(&zhdr->buddy);
+ INIT_WORK(&zhdr->work, compact_page_work);
+ return zhdr;
+}
+
+/* Resets the struct page fields and frees the page */
+static void free_z3fold_page(struct page *page)
+{
+ __free_page(page);
+}
+
+/* Lock a z3fold page */
+static inline void z3fold_page_lock(struct z3fold_header *zhdr)
+{
+ spin_lock(&zhdr->page_lock);
+}
+
+/* Try to lock a z3fold page */
+static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
+{
+ return spin_trylock(&zhdr->page_lock);
+}
+
+/* Unlock a z3fold page */
+static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
+{
+ spin_unlock(&zhdr->page_lock);
+}
+
+/*
+ * 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;
+ if (bud == LAST)
+ handle |= (zhdr->last_chunks << BUDDY_SHIFT);
+ }
+ 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);
+}
+
+/* only for LAST bud, returns zero otherwise */
+static unsigned short handle_to_chunks(unsigned long handle)
+{
+ return (handle & ~PAGE_MASK) >> BUDDY_SHIFT;
+}
+
+/*
+ * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
+ * but that doesn't matter. because the masking will result in the
+ * correct 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;
+}
+
+static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
+{
+ struct page *page = virt_to_page(zhdr);
+ struct z3fold_pool *pool = zhdr->pool;
+
+ WARN_ON(!list_empty(&zhdr->buddy));
+ set_bit(PAGE_STALE, &page->private);
+ clear_bit(NEEDS_COMPACTING, &page->private);
+ spin_lock(&pool->lock);
+ if (!list_empty(&page->lru))
+ list_del(&page->lru);
+ spin_unlock(&pool->lock);
+ if (locked)
+ z3fold_page_unlock(zhdr);
+ spin_lock(&pool->stale_lock);
+ list_add(&zhdr->buddy, &pool->stale);
+ queue_work(pool->release_wq, &pool->work);
+ spin_unlock(&pool->stale_lock);
+}
+
+static void __attribute__((__unused__))
+ release_z3fold_page(struct kref *ref)
+{
+ struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
+ refcount);
+ __release_z3fold_page(zhdr, false);
+}
+
+static void release_z3fold_page_locked(struct kref *ref)
+{
+ struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
+ refcount);
+ WARN_ON(z3fold_page_trylock(zhdr));
+ __release_z3fold_page(zhdr, true);
+}
+
+static void release_z3fold_page_locked_list(struct kref *ref)
+{
+ struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
+ refcount);
+ spin_lock(&zhdr->pool->lock);
+ list_del_init(&zhdr->buddy);
+ spin_unlock(&zhdr->pool->lock);
+
+ WARN_ON(z3fold_page_trylock(zhdr));
+ __release_z3fold_page(zhdr, true);
+}
+
+static void free_pages_work(struct work_struct *w)
+{
+ struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
+
+ spin_lock(&pool->stale_lock);
+ while (!list_empty(&pool->stale)) {
+ struct z3fold_header *zhdr = list_first_entry(&pool->stale,
+ struct z3fold_header, buddy);
+ struct page *page = virt_to_page(zhdr);
+
+ list_del(&zhdr->buddy);
+ if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
+ continue;
+ spin_unlock(&pool->stale_lock);
+ cancel_work_sync(&zhdr->work);
+ free_z3fold_page(page);
+ cond_resched();
+ spin_lock(&pool->stale_lock);
+ }
+ spin_unlock(&pool->stale_lock);
+}
+
+/*
+ * 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 - ZHDR_CHUNKS;
+ int nfree_after = zhdr->last_chunks ?
+ 0 : TOTAL_CHUNKS -
+ (zhdr->start_middle + zhdr->middle_chunks);
+ nfree = max(nfree_before, nfree_after);
+ } else
+ nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
+ return nfree;
+}
+
+static inline void *mchunk_memmove(struct z3fold_header *zhdr,
+ unsigned short dst_chunk)
+{
+ void *beg = zhdr;
+ return memmove(beg + (dst_chunk << CHUNK_SHIFT),
+ beg + (zhdr->start_middle << CHUNK_SHIFT),
+ zhdr->middle_chunks << CHUNK_SHIFT);
+}
+
+#define BIG_CHUNK_GAP 3
+/* Has to be called with lock held */
+static int z3fold_compact_page(struct z3fold_header *zhdr)
+{
+ struct page *page = virt_to_page(zhdr);
+
+ if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
+ return 0; /* can't move middle chunk, it's used */
+
+ if (zhdr->middle_chunks == 0)
+ return 0; /* nothing to compact */
+
+ if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
+ /* move to the beginning */
+ mchunk_memmove(zhdr, ZHDR_CHUNKS);
+ zhdr->first_chunks = zhdr->middle_chunks;
+ zhdr->middle_chunks = 0;
+ zhdr->start_middle = 0;
+ zhdr->first_num++;
+ return 1;
+ }
+
+ /*
+ * moving data is expensive, so let's only do that if
+ * there's substantial gain (at least BIG_CHUNK_GAP chunks)
+ */
+ if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
+ zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
+ BIG_CHUNK_GAP) {
+ mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
+ zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
+ return 1;
+ } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
+ TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
+ + zhdr->middle_chunks) >=
+ BIG_CHUNK_GAP) {
+ unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
+ zhdr->middle_chunks;
+ mchunk_memmove(zhdr, new_start);
+ zhdr->start_middle = new_start;
+ return 1;
+ }
+
+ return 0;
+}
+
+static void do_compact_page(struct z3fold_header *zhdr, bool locked)
+{
+ struct z3fold_pool *pool = zhdr->pool;
+ struct page *page;
+ struct list_head *unbuddied;
+ int fchunks;
+
+ page = virt_to_page(zhdr);
+ if (locked)
+ WARN_ON(z3fold_page_trylock(zhdr));
+ else
+ z3fold_page_lock(zhdr);
+ if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
+ z3fold_page_unlock(zhdr);
+ return;
+ }
+ spin_lock(&pool->lock);
+ list_del_init(&zhdr->buddy);
+ spin_unlock(&pool->lock);
+
+ if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
+ atomic64_dec(&pool->pages_nr);
+ return;
+ }
+
+ z3fold_compact_page(zhdr);
+ unbuddied = get_cpu_ptr(pool->unbuddied);
+ fchunks = num_free_chunks(zhdr);
+ if (fchunks < NCHUNKS &&
+ (!zhdr->first_chunks || !zhdr->middle_chunks ||
+ !zhdr->last_chunks)) {
+ /* the page's not completely free and it's unbuddied */
+ spin_lock(&pool->lock);
+ list_add(&zhdr->buddy, &unbuddied[fchunks]);
+ spin_unlock(&pool->lock);
+ zhdr->cpu = smp_processor_id();
+ }
+ put_cpu_ptr(pool->unbuddied);
+ z3fold_page_unlock(zhdr);
+}
+
+static void compact_page_work(struct work_struct *w)
+{
+ struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
+ work);
+
+ do_compact_page(zhdr, false);
+}
+
+
+/*
+ * API Functions
+ */
+
+/**
+ * z3fold_create_pool() - create a new z3fold pool
+ * @name: pool name
+ * @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(const char *name, gfp_t gfp,
+ const struct z3fold_ops *ops)
+{
+ struct z3fold_pool *pool = NULL;
+ int i, cpu;
+
+ pool = kzalloc(sizeof(struct z3fold_pool), gfp);
+ if (!pool)
+ goto out;
+ spin_lock_init(&pool->lock);
+ spin_lock_init(&pool->stale_lock);
+ pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
+ if (!pool->unbuddied)
+ goto out_pool;
+ for_each_possible_cpu(cpu) {
+ struct list_head *unbuddied =
+ per_cpu_ptr(pool->unbuddied, cpu);
+ for_each_unbuddied_list(i, 0)
+ INIT_LIST_HEAD(&unbuddied[i]);
+ }
+ INIT_LIST_HEAD(&pool->lru);
+ INIT_LIST_HEAD(&pool->stale);
+ atomic64_set(&pool->pages_nr, 0);
+ pool->name = name;
+ pool->compact_wq = create_singlethread_workqueue(pool->name);
+ if (!pool->compact_wq)
+ goto out_unbuddied;
+ pool->release_wq = create_singlethread_workqueue(pool->name);
+ if (!pool->release_wq)
+ goto out_wq;
+ INIT_WORK(&pool->work, free_pages_work);
+ pool->ops = ops;
+ return pool;
+
+out_wq:
+ destroy_workqueue(pool->compact_wq);
+out_unbuddied:
+ free_percpu(pool->unbuddied);
+out_pool:
+ kfree(pool);
+out:
+ return NULL;
+}
+
+/**
+ * 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)
+{
+ destroy_workqueue(pool->release_wq);
+ destroy_workqueue(pool->compact_wq);
+ kfree(pool);
+}
+
+/**
+ * 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;
+ struct page *page = NULL;
+ enum buddy bud;
+ bool can_sleep = gfpflags_allow_blocking(gfp);
+
+ 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 {
+ struct list_head *unbuddied;
+ chunks = size_to_chunks(size);
+
+lookup:
+ /* First, try to find an unbuddied z3fold page. */
+ unbuddied = get_cpu_ptr(pool->unbuddied);
+ for_each_unbuddied_list(i, chunks) {
+ struct list_head *l = &unbuddied[i];
+
+ zhdr = list_first_entry_or_null(READ_ONCE(l),
+ struct z3fold_header, buddy);
+
+ if (!zhdr)
+ continue;
+
+ /* Re-check under lock. */
+ spin_lock(&pool->lock);
+ l = &unbuddied[i];
+ if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
+ struct z3fold_header, buddy)) ||
+ !z3fold_page_trylock(zhdr)) {
+ spin_unlock(&pool->lock);
+ put_cpu_ptr(pool->unbuddied);
+ goto lookup;
+ }
+ list_del_init(&zhdr->buddy);
+ zhdr->cpu = -1;
+ spin_unlock(&pool->lock);
+
+ page = virt_to_page(zhdr);
+ if (test_bit(NEEDS_COMPACTING, &page->private)) {
+ z3fold_page_unlock(zhdr);
+ zhdr = NULL;
+ put_cpu_ptr(pool->unbuddied);
+ if (can_sleep)
+ cond_resched();
+ goto lookup;
+ }
+
+ /*
+ * this page could not be removed from its unbuddied
+ * list while pool lock was held, and then we've taken
+ * page lock so kref_put could not be called before
+ * we got here, so it's safe to just call kref_get()
+ */
+ kref_get(&zhdr->refcount);
+ break;
+ }
+ put_cpu_ptr(pool->unbuddied);
+
+ if (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 {
+ if (kref_put(&zhdr->refcount,
+ release_z3fold_page_locked))
+ atomic64_dec(&pool->pages_nr);
+ else
+ z3fold_page_unlock(zhdr);
+ pr_err("No free chunks in unbuddied\n");
+ WARN_ON(1);
+ goto lookup;
+ }
+ goto found;
+ }
+ bud = FIRST;
+ }
+
+ page = NULL;
+ if (can_sleep) {
+ spin_lock(&pool->stale_lock);
+ zhdr = list_first_entry_or_null(&pool->stale,
+ struct z3fold_header, buddy);
+ /*
+ * Before allocating a page, let's see if we can take one from
+ * the stale pages list. cancel_work_sync() can sleep so we
+ * limit this case to the contexts where we can sleep
+ */
+ if (zhdr) {
+ list_del(&zhdr->buddy);
+ spin_unlock(&pool->stale_lock);
+ cancel_work_sync(&zhdr->work);
+ page = virt_to_page(zhdr);
+ } else {
+ spin_unlock(&pool->stale_lock);
+ }
+ }
+ if (!page)
+ page = alloc_page(gfp);
+
+ if (!page)
+ return -ENOMEM;
+
+ atomic64_inc(&pool->pages_nr);
+ zhdr = init_z3fold_page(page, pool);
+
+ if (bud == HEADLESS) {
+ set_bit(PAGE_HEADLESS, &page->private);
+ goto headless;
+ }
+ z3fold_page_lock(zhdr);
+
+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 + ZHDR_CHUNKS;
+ }
+
+ if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
+ zhdr->middle_chunks == 0) {
+ struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
+
+ /* Add to unbuddied list */
+ freechunks = num_free_chunks(zhdr);
+ spin_lock(&pool->lock);
+ list_add(&zhdr->buddy, &unbuddied[freechunks]);
+ spin_unlock(&pool->lock);
+ zhdr->cpu = smp_processor_id();
+ put_cpu_ptr(pool->unbuddied);
+ }
+
+headless:
+ spin_lock(&pool->lock);
+ /* 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);
+ if (bud != HEADLESS)
+ z3fold_page_unlock(zhdr);
+
+ 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;
+ struct page *page;
+ enum buddy bud;
+
+ zhdr = handle_to_z3fold_header(handle);
+ page = virt_to_page(zhdr);
+
+ if (test_bit(PAGE_HEADLESS, &page->private)) {
+ /* if a headless page is under reclaim, just leave.
+ * NB: we use test_and_set_bit for a reason: if the bit
+ * has not been set before, we release this page
+ * immediately so we don't care about its value any more.
+ */
+ if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
+ spin_lock(&pool->lock);
+ list_del(&page->lru);
+ spin_unlock(&pool->lock);
+ free_z3fold_page(page);
+ atomic64_dec(&pool->pages_nr);
+ }
+ return;
+ }
+
+ /* Non-headless case */
+ z3fold_page_lock(zhdr);
+ bud = handle_to_buddy(handle);
+
+ switch (bud) {
+ case FIRST:
+ zhdr->first_chunks = 0;
+ break;
+ case MIDDLE:
+ zhdr->middle_chunks = 0;
+ break;
+ case LAST:
+ zhdr->last_chunks = 0;
+ break;
+ default:
+ pr_err("%s: unknown bud %d\n", __func__, bud);
+ WARN_ON(1);
+ z3fold_page_unlock(zhdr);
+ return;
+ }
+
+ if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
+ atomic64_dec(&pool->pages_nr);
+ return;
+ }
+ if (test_bit(PAGE_CLAIMED, &page->private)) {
+ z3fold_page_unlock(zhdr);
+ return;
+ }
+ if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
+ z3fold_page_unlock(zhdr);
+ return;
+ }
+ if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
+ spin_lock(&pool->lock);
+ list_del_init(&zhdr->buddy);
+ spin_unlock(&pool->lock);
+ zhdr->cpu = -1;
+ kref_get(&zhdr->refcount);
+ do_compact_page(zhdr, true);
+ return;
+ }
+ kref_get(&zhdr->refcount);
+ queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
+ z3fold_page_unlock(zhdr);
+}
+
+/**
+ * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
+ * @pool: pool from which a page will attempt to be evicted
+ * @retries: 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;
+ struct z3fold_header *zhdr = NULL;
+ struct page *page = NULL;
+ struct list_head *pos;
+ unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
+
+ spin_lock(&pool->lock);
+ if (!pool->ops || !pool->ops->evict || retries == 0) {
+ spin_unlock(&pool->lock);
+ return -EINVAL;
+ }
+ for (i = 0; i < retries; i++) {
+ if (list_empty(&pool->lru)) {
+ spin_unlock(&pool->lock);
+ return -EINVAL;
+ }
+ list_for_each_prev(pos, &pool->lru) {
+ page = list_entry(pos, struct page, lru);
+
+ /* this bit could have been set by free, in which case
+ * we pass over to the next page in the pool.
+ */
+ if (test_and_set_bit(PAGE_CLAIMED, &page->private))
+ continue;
+
+ zhdr = page_address(page);
+ if (test_bit(PAGE_HEADLESS, &page->private))
+ break;
+
+ if (!z3fold_page_trylock(zhdr)) {
+ zhdr = NULL;
+ continue; /* can't evict at this point */
+ }
+ kref_get(&zhdr->refcount);
+ list_del_init(&zhdr->buddy);
+ zhdr->cpu = -1;
+ break;
+ }
+
+ if (!zhdr)
+ break;
+
+ list_del_init(&page->lru);
+ spin_unlock(&pool->lock);
+
+ if (!test_bit(PAGE_HEADLESS, &page->private)) {
+ /*
+ * 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);
+ /*
+ * it's safe to unlock here because we hold a
+ * reference to this page
+ */
+ z3fold_page_unlock(zhdr);
+ } else {
+ first_handle = encode_handle(zhdr, HEADLESS);
+ last_handle = middle_handle = 0;
+ }
+
+ /* 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:
+ if (test_bit(PAGE_HEADLESS, &page->private)) {
+ if (ret == 0) {
+ free_z3fold_page(page);
+ atomic64_dec(&pool->pages_nr);
+ return 0;
+ }
+ spin_lock(&pool->lock);
+ list_add(&page->lru, &pool->lru);
+ spin_unlock(&pool->lock);
+ } else {
+ z3fold_page_lock(zhdr);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ if (kref_put(&zhdr->refcount,
+ release_z3fold_page_locked)) {
+ atomic64_dec(&pool->pages_nr);
+ return 0;
+ }
+ /*
+ * if we are here, the page is still not completely
+ * free. Take the global pool lock then to be able
+ * to add it back to the lru list
+ */
+ spin_lock(&pool->lock);
+ list_add(&page->lru, &pool->lru);
+ spin_unlock(&pool->lock);
+ z3fold_page_unlock(zhdr);
+ }
+
+ /* We started off locked to we need to lock the pool back */
+ spin_lock(&pool->lock);
+ }
+ 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;
+
+ zhdr = handle_to_z3fold_header(handle);
+ addr = zhdr;
+ page = virt_to_page(zhdr);
+
+ if (test_bit(PAGE_HEADLESS, &page->private))
+ goto out;
+
+ z3fold_page_lock(zhdr);
+ 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 - (handle_to_chunks(handle) << CHUNK_SHIFT);
+ break;
+ default:
+ pr_err("unknown buddy id %d\n", buddy);
+ WARN_ON(1);
+ addr = NULL;
+ break;
+ }
+
+ z3fold_page_unlock(zhdr);
+out:
+ 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;
+
+ zhdr = handle_to_z3fold_header(handle);
+ page = virt_to_page(zhdr);
+
+ if (test_bit(PAGE_HEADLESS, &page->private))
+ return;
+
+ z3fold_page_lock(zhdr);
+ buddy = handle_to_buddy(handle);
+ if (buddy == MIDDLE)
+ clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
+ z3fold_page_unlock(zhdr);
+}
+
+/**
+ * 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.
+ */
+static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
+{
+ return atomic64_read(&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(name, 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 is not larger than the page size */
+ BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
+ 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");