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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
commit5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch)
treea94efe259b9009378be6d90eb30d2b019d95c194 /mm/z3fold.c
parentInitial commit. (diff)
downloadlinux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.tar.xz
linux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.zip
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'mm/z3fold.c')
-rw-r--r--mm/z3fold.c1832
1 files changed, 1832 insertions, 0 deletions
diff --git a/mm/z3fold.c b/mm/z3fold.c
new file mode 100644
index 000000000..912ac9a64
--- /dev/null
+++ b/mm/z3fold.c
@@ -0,0 +1,1832 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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/cpumask.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/page-flags.h>
+#include <linux/migrate.h>
+#include <linux/node.h>
+#include <linux/compaction.h>
+#include <linux/percpu.h>
+#include <linux/mount.h>
+#include <linux/pseudo_fs.h>
+#include <linux/fs.h>
+#include <linux/preempt.h>
+#include <linux/workqueue.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/zpool.h>
+#include <linux/magic.h>
+#include <linux/kmemleak.h>
+
+/*
+ * 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
+#define SLOTS_ALIGN (0x40)
+
+/*****************
+ * 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 = LAST
+};
+
+struct z3fold_buddy_slots {
+ /*
+ * we are using BUDDY_MASK in handle_to_buddy etc. so there should
+ * be enough slots to hold all possible variants
+ */
+ unsigned long slot[BUDDY_MASK + 1];
+ unsigned long pool; /* back link */
+ rwlock_t lock;
+};
+#define HANDLE_FLAG_MASK (0x03)
+
+/*
+ * 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
+ * @slots: pointer to the structure holding buddy slots
+ * @pool: pointer to the containing pool
+ * @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)
+ * @mapped_count: the number of objects currently mapped
+ */
+struct z3fold_header {
+ struct list_head buddy;
+ spinlock_t page_lock;
+ struct kref refcount;
+ struct work_struct work;
+ struct z3fold_buddy_slots *slots;
+ 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;
+ unsigned short mapped_count:2;
+ unsigned short foreign_handles: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.
+ * @c_handle: cache for z3fold_buddy_slots allocation
+ * @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
+ * @inode: inode for z3fold pseudo filesystem
+ *
+ * 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;
+ struct kmem_cache *c_handle;
+ 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;
+ struct inode *inode;
+};
+
+/*
+ * 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 */
+};
+
+/*
+ * handle flags, go under HANDLE_FLAG_MASK
+ */
+enum z3fold_handle_flags {
+ HANDLES_NOFREE = 0,
+};
+
+/*
+ * Forward declarations
+ */
+static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
+static void compact_page_work(struct work_struct *w);
+
+/*****************
+ * 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 inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
+ gfp_t gfp)
+{
+ struct z3fold_buddy_slots *slots;
+
+ slots = kmem_cache_zalloc(pool->c_handle,
+ (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
+
+ if (slots) {
+ /* It will be freed separately in free_handle(). */
+ kmemleak_not_leak(slots);
+ slots->pool = (unsigned long)pool;
+ rwlock_init(&slots->lock);
+ }
+
+ return slots;
+}
+
+static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
+{
+ return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
+}
+
+static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
+{
+ return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
+}
+
+/* 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);
+}
+
+
+static inline struct z3fold_header *__get_z3fold_header(unsigned long handle,
+ bool lock)
+{
+ struct z3fold_buddy_slots *slots;
+ struct z3fold_header *zhdr;
+ int locked = 0;
+
+ if (!(handle & (1 << PAGE_HEADLESS))) {
+ slots = handle_to_slots(handle);
+ do {
+ unsigned long addr;
+
+ read_lock(&slots->lock);
+ addr = *(unsigned long *)handle;
+ zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
+ if (lock)
+ locked = z3fold_page_trylock(zhdr);
+ read_unlock(&slots->lock);
+ if (locked)
+ break;
+ cpu_relax();
+ } while (lock);
+ } else {
+ zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
+ }
+
+ return zhdr;
+}
+
+/* Returns the z3fold page where a given handle is stored */
+static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
+{
+ return __get_z3fold_header(h, false);
+}
+
+/* return locked z3fold page if it's not headless */
+static inline struct z3fold_header *get_z3fold_header(unsigned long h)
+{
+ return __get_z3fold_header(h, true);
+}
+
+static inline void put_z3fold_header(struct z3fold_header *zhdr)
+{
+ struct page *page = virt_to_page(zhdr);
+
+ if (!test_bit(PAGE_HEADLESS, &page->private))
+ z3fold_page_unlock(zhdr);
+}
+
+static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
+{
+ struct z3fold_buddy_slots *slots;
+ int i;
+ bool is_free;
+
+ if (handle & (1 << PAGE_HEADLESS))
+ return;
+
+ if (WARN_ON(*(unsigned long *)handle == 0))
+ return;
+
+ slots = handle_to_slots(handle);
+ write_lock(&slots->lock);
+ *(unsigned long *)handle = 0;
+
+ if (test_bit(HANDLES_NOFREE, &slots->pool)) {
+ write_unlock(&slots->lock);
+ return; /* simple case, nothing else to do */
+ }
+
+ if (zhdr->slots != slots)
+ zhdr->foreign_handles--;
+
+ is_free = true;
+ for (i = 0; i <= BUDDY_MASK; i++) {
+ if (slots->slot[i]) {
+ is_free = false;
+ break;
+ }
+ }
+ write_unlock(&slots->lock);
+
+ if (is_free) {
+ struct z3fold_pool *pool = slots_to_pool(slots);
+
+ if (zhdr->slots == slots)
+ zhdr->slots = NULL;
+ kmem_cache_free(pool->c_handle, slots);
+ }
+}
+
+static int z3fold_init_fs_context(struct fs_context *fc)
+{
+ return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
+}
+
+static struct file_system_type z3fold_fs = {
+ .name = "z3fold",
+ .init_fs_context = z3fold_init_fs_context,
+ .kill_sb = kill_anon_super,
+};
+
+static struct vfsmount *z3fold_mnt;
+static int z3fold_mount(void)
+{
+ int ret = 0;
+
+ z3fold_mnt = kern_mount(&z3fold_fs);
+ if (IS_ERR(z3fold_mnt))
+ ret = PTR_ERR(z3fold_mnt);
+
+ return ret;
+}
+
+static void z3fold_unmount(void)
+{
+ kern_unmount(z3fold_mnt);
+}
+
+static const struct address_space_operations z3fold_aops;
+static int z3fold_register_migration(struct z3fold_pool *pool)
+{
+ pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
+ if (IS_ERR(pool->inode)) {
+ pool->inode = NULL;
+ return 1;
+ }
+
+ pool->inode->i_mapping->private_data = pool;
+ pool->inode->i_mapping->a_ops = &z3fold_aops;
+ return 0;
+}
+
+static void z3fold_unregister_migration(struct z3fold_pool *pool)
+{
+ if (pool->inode)
+ iput(pool->inode);
+ }
+
+/* Initializes the z3fold header of a newly allocated z3fold page */
+static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
+ struct z3fold_pool *pool, gfp_t gfp)
+{
+ struct z3fold_header *zhdr = page_address(page);
+ struct z3fold_buddy_slots *slots;
+
+ 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);
+ if (headless)
+ return zhdr;
+
+ slots = alloc_slots(pool, gfp);
+ if (!slots)
+ return NULL;
+
+ 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->foreign_handles = 0;
+ zhdr->mapped_count = 0;
+ zhdr->slots = slots;
+ 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, bool headless)
+{
+ if (!headless) {
+ lock_page(page);
+ __ClearPageMovable(page);
+ unlock_page(page);
+ }
+ ClearPagePrivate(page);
+ __free_page(page);
+}
+
+/* Helper function to build the index */
+static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
+{
+ return (bud + zhdr->first_num) & BUDDY_MASK;
+}
+
+/*
+ * 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,
+ struct z3fold_buddy_slots *slots,
+ enum buddy bud)
+{
+ unsigned long h = (unsigned long)zhdr;
+ int idx = 0;
+
+ /*
+ * For a headless page, its handle is its pointer with the extra
+ * PAGE_HEADLESS bit set
+ */
+ if (bud == HEADLESS)
+ return h | (1 << PAGE_HEADLESS);
+
+ /* otherwise, return pointer to encoded handle */
+ idx = __idx(zhdr, bud);
+ h += idx;
+ if (bud == LAST)
+ h |= (zhdr->last_chunks << BUDDY_SHIFT);
+
+ write_lock(&slots->lock);
+ slots->slot[idx] = h;
+ write_unlock(&slots->lock);
+ return (unsigned long)&slots->slot[idx];
+}
+
+static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
+{
+ return __encode_handle(zhdr, zhdr->slots, bud);
+}
+
+/* only for LAST bud, returns zero otherwise */
+static unsigned short handle_to_chunks(unsigned long handle)
+{
+ struct z3fold_buddy_slots *slots = handle_to_slots(handle);
+ unsigned long addr;
+
+ read_lock(&slots->lock);
+ addr = *(unsigned long *)handle;
+ read_unlock(&slots->lock);
+ return (addr & ~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;
+ struct z3fold_buddy_slots *slots = handle_to_slots(handle);
+ unsigned long addr;
+
+ read_lock(&slots->lock);
+ WARN_ON(handle & (1 << PAGE_HEADLESS));
+ addr = *(unsigned long *)handle;
+ read_unlock(&slots->lock);
+ zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
+ return (addr - zhdr->first_num) & BUDDY_MASK;
+}
+
+static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
+{
+ return zhdr->pool;
+}
+
+static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
+{
+ struct page *page = virt_to_page(zhdr);
+ struct z3fold_pool *pool = zhdr_to_pool(zhdr);
+
+ 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_init(&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);
+ struct z3fold_pool *pool = zhdr_to_pool(zhdr);
+
+ spin_lock(&pool->lock);
+ list_del_init(&zhdr->buddy);
+ spin_unlock(&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, false);
+ 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;
+}
+
+/* Add to the appropriate unbuddied list */
+static inline void add_to_unbuddied(struct z3fold_pool *pool,
+ struct z3fold_header *zhdr)
+{
+ if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
+ zhdr->middle_chunks == 0) {
+ struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
+
+ int 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);
+ }
+}
+
+static inline enum buddy get_free_buddy(struct z3fold_header *zhdr, int chunks)
+{
+ enum buddy bud = HEADLESS;
+
+ if (zhdr->middle_chunks) {
+ if (!zhdr->first_chunks &&
+ chunks <= zhdr->start_middle - ZHDR_CHUNKS)
+ bud = FIRST;
+ else if (!zhdr->last_chunks)
+ bud = LAST;
+ } else {
+ if (!zhdr->first_chunks)
+ bud = FIRST;
+ else if (!zhdr->last_chunks)
+ bud = LAST;
+ else
+ bud = MIDDLE;
+ }
+
+ return bud;
+}
+
+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);
+}
+
+static inline bool buddy_single(struct z3fold_header *zhdr)
+{
+ return !((zhdr->first_chunks && zhdr->middle_chunks) ||
+ (zhdr->first_chunks && zhdr->last_chunks) ||
+ (zhdr->middle_chunks && zhdr->last_chunks));
+}
+
+static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
+{
+ struct z3fold_pool *pool = zhdr_to_pool(zhdr);
+ void *p = zhdr;
+ unsigned long old_handle = 0;
+ size_t sz = 0;
+ struct z3fold_header *new_zhdr = NULL;
+ int first_idx = __idx(zhdr, FIRST);
+ int middle_idx = __idx(zhdr, MIDDLE);
+ int last_idx = __idx(zhdr, LAST);
+ unsigned short *moved_chunks = NULL;
+
+ /*
+ * No need to protect slots here -- all the slots are "local" and
+ * the page lock is already taken
+ */
+ if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
+ p += ZHDR_SIZE_ALIGNED;
+ sz = zhdr->first_chunks << CHUNK_SHIFT;
+ old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
+ moved_chunks = &zhdr->first_chunks;
+ } else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
+ p += zhdr->start_middle << CHUNK_SHIFT;
+ sz = zhdr->middle_chunks << CHUNK_SHIFT;
+ old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
+ moved_chunks = &zhdr->middle_chunks;
+ } else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
+ p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
+ sz = zhdr->last_chunks << CHUNK_SHIFT;
+ old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
+ moved_chunks = &zhdr->last_chunks;
+ }
+
+ if (sz > 0) {
+ enum buddy new_bud = HEADLESS;
+ short chunks = size_to_chunks(sz);
+ void *q;
+
+ new_zhdr = __z3fold_alloc(pool, sz, false);
+ if (!new_zhdr)
+ return NULL;
+
+ if (WARN_ON(new_zhdr == zhdr))
+ goto out_fail;
+
+ new_bud = get_free_buddy(new_zhdr, chunks);
+ q = new_zhdr;
+ switch (new_bud) {
+ case FIRST:
+ new_zhdr->first_chunks = chunks;
+ q += ZHDR_SIZE_ALIGNED;
+ break;
+ case MIDDLE:
+ new_zhdr->middle_chunks = chunks;
+ new_zhdr->start_middle =
+ new_zhdr->first_chunks + ZHDR_CHUNKS;
+ q += new_zhdr->start_middle << CHUNK_SHIFT;
+ break;
+ case LAST:
+ new_zhdr->last_chunks = chunks;
+ q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
+ break;
+ default:
+ goto out_fail;
+ }
+ new_zhdr->foreign_handles++;
+ memcpy(q, p, sz);
+ write_lock(&zhdr->slots->lock);
+ *(unsigned long *)old_handle = (unsigned long)new_zhdr +
+ __idx(new_zhdr, new_bud);
+ if (new_bud == LAST)
+ *(unsigned long *)old_handle |=
+ (new_zhdr->last_chunks << BUDDY_SHIFT);
+ write_unlock(&zhdr->slots->lock);
+ add_to_unbuddied(pool, new_zhdr);
+ z3fold_page_unlock(new_zhdr);
+
+ *moved_chunks = 0;
+ }
+
+ return new_zhdr;
+
+out_fail:
+ if (new_zhdr) {
+ if (kref_put(&new_zhdr->refcount, release_z3fold_page_locked))
+ atomic64_dec(&pool->pages_nr);
+ else {
+ add_to_unbuddied(pool, new_zhdr);
+ z3fold_page_unlock(new_zhdr);
+ }
+ }
+ return NULL;
+
+}
+
+#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 (unlikely(PageIsolated(page)))
+ return 0;
+
+ 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_to_pool(zhdr);
+ struct page *page;
+
+ 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;
+ }
+
+ if (test_bit(PAGE_STALE, &page->private) ||
+ test_and_set_bit(PAGE_CLAIMED, &page->private)) {
+ z3fold_page_unlock(zhdr);
+ return;
+ }
+
+ if (!zhdr->foreign_handles && buddy_single(zhdr) &&
+ zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
+ if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
+ atomic64_dec(&pool->pages_nr);
+ else {
+ clear_bit(PAGE_CLAIMED, &page->private);
+ z3fold_page_unlock(zhdr);
+ }
+ return;
+ }
+
+ z3fold_compact_page(zhdr);
+ add_to_unbuddied(pool, zhdr);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ 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);
+}
+
+/* returns _locked_ z3fold page header or NULL */
+static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
+ size_t size, bool can_sleep)
+{
+ struct z3fold_header *zhdr = NULL;
+ struct page *page;
+ struct list_head *unbuddied;
+ int chunks = size_to_chunks(size), i;
+
+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);
+ zhdr = NULL;
+ put_cpu_ptr(pool->unbuddied);
+ if (can_sleep)
+ cond_resched();
+ 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) ||
+ test_bit(PAGE_CLAIMED, &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) {
+ int cpu;
+
+ /* look for _exact_ match on other cpus' lists */
+ for_each_online_cpu(cpu) {
+ struct list_head *l;
+
+ unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
+ spin_lock(&pool->lock);
+ l = &unbuddied[chunks];
+
+ zhdr = list_first_entry_or_null(READ_ONCE(l),
+ struct z3fold_header, buddy);
+
+ if (!zhdr || !z3fold_page_trylock(zhdr)) {
+ spin_unlock(&pool->lock);
+ zhdr = NULL;
+ continue;
+ }
+ list_del_init(&zhdr->buddy);
+ zhdr->cpu = -1;
+ spin_unlock(&pool->lock);
+
+ page = virt_to_page(zhdr);
+ if (test_bit(NEEDS_COMPACTING, &page->private) ||
+ test_bit(PAGE_CLAIMED, &page->private)) {
+ z3fold_page_unlock(zhdr);
+ zhdr = NULL;
+ if (can_sleep)
+ cond_resched();
+ continue;
+ }
+ kref_get(&zhdr->refcount);
+ break;
+ }
+ }
+
+ if (zhdr && !zhdr->slots)
+ zhdr->slots = alloc_slots(pool,
+ can_sleep ? GFP_NOIO : GFP_ATOMIC);
+ return zhdr;
+}
+
+/*
+ * 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;
+ pool->c_handle = kmem_cache_create("z3fold_handle",
+ sizeof(struct z3fold_buddy_slots),
+ SLOTS_ALIGN, 0, NULL);
+ if (!pool->c_handle)
+ goto out_c;
+ 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;
+ if (z3fold_register_migration(pool))
+ goto out_rwq;
+ INIT_WORK(&pool->work, free_pages_work);
+ pool->ops = ops;
+ return pool;
+
+out_rwq:
+ destroy_workqueue(pool->release_wq);
+out_wq:
+ destroy_workqueue(pool->compact_wq);
+out_unbuddied:
+ free_percpu(pool->unbuddied);
+out_pool:
+ kmem_cache_destroy(pool->c_handle);
+out_c:
+ 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)
+{
+ kmem_cache_destroy(pool->c_handle);
+
+ /*
+ * We need to destroy pool->compact_wq before pool->release_wq,
+ * as any pending work on pool->compact_wq will call
+ * queue_work(pool->release_wq, &pool->work).
+ *
+ * There are still outstanding pages until both workqueues are drained,
+ * so we cannot unregister migration until then.
+ */
+
+ destroy_workqueue(pool->compact_wq);
+ destroy_workqueue(pool->release_wq);
+ z3fold_unregister_migration(pool);
+ free_percpu(pool->unbuddied);
+ 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 = size_to_chunks(size);
+ struct z3fold_header *zhdr = NULL;
+ struct page *page = NULL;
+ enum buddy bud;
+ bool can_sleep = gfpflags_allow_blocking(gfp);
+
+ if (!size)
+ return -EINVAL;
+
+ if (size > PAGE_SIZE)
+ return -ENOSPC;
+
+ if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
+ bud = HEADLESS;
+ else {
+retry:
+ zhdr = __z3fold_alloc(pool, size, can_sleep);
+ if (zhdr) {
+ bud = get_free_buddy(zhdr, chunks);
+ if (bud == HEADLESS) {
+ 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 retry;
+ }
+ page = virt_to_page(zhdr);
+ 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;
+
+ zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
+ if (!zhdr) {
+ __free_page(page);
+ return -ENOMEM;
+ }
+ atomic64_inc(&pool->pages_nr);
+
+ if (bud == HEADLESS) {
+ set_bit(PAGE_HEADLESS, &page->private);
+ goto headless;
+ }
+ if (can_sleep) {
+ lock_page(page);
+ __SetPageMovable(page, pool->inode->i_mapping);
+ unlock_page(page);
+ } else {
+ if (trylock_page(page)) {
+ __SetPageMovable(page, pool->inode->i_mapping);
+ unlock_page(page);
+ }
+ }
+ 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;
+ }
+ add_to_unbuddied(pool, zhdr);
+
+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;
+ bool page_claimed;
+
+ zhdr = get_z3fold_header(handle);
+ page = virt_to_page(zhdr);
+ page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
+
+ 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 (!page_claimed) {
+ spin_lock(&pool->lock);
+ list_del(&page->lru);
+ spin_unlock(&pool->lock);
+ put_z3fold_header(zhdr);
+ free_z3fold_page(page, true);
+ atomic64_dec(&pool->pages_nr);
+ }
+ return;
+ }
+
+ /* Non-headless case */
+ 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);
+ put_z3fold_header(zhdr);
+ return;
+ }
+
+ if (!page_claimed)
+ free_handle(handle, zhdr);
+ if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
+ atomic64_dec(&pool->pages_nr);
+ return;
+ }
+ if (page_claimed) {
+ /* the page has not been claimed by us */
+ z3fold_page_unlock(zhdr);
+ return;
+ }
+ if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
+ put_z3fold_header(zhdr);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ 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);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ do_compact_page(zhdr, true);
+ return;
+ }
+ kref_get(&zhdr->refcount);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
+ put_z3fold_header(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 = -1;
+ struct z3fold_header *zhdr = NULL;
+ struct page *page = NULL;
+ struct list_head *pos;
+ unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
+ struct z3fold_buddy_slots slots __attribute__((aligned(SLOTS_ALIGN)));
+
+ rwlock_init(&slots.lock);
+ slots.pool = (unsigned long)pool | (1 << HANDLES_NOFREE);
+
+ 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);
+
+ zhdr = page_address(page);
+ if (test_bit(PAGE_HEADLESS, &page->private)) {
+ /*
+ * For non-headless pages, we wait to do this
+ * until we have the page lock to avoid racing
+ * with __z3fold_alloc(). Headless pages don't
+ * have a lock (and __z3fold_alloc() will never
+ * see them), but we still need to test and set
+ * PAGE_CLAIMED to avoid racing with
+ * z3fold_free(), so just do it now before
+ * leaving the loop.
+ */
+ if (test_and_set_bit(PAGE_CLAIMED, &page->private))
+ continue;
+
+ break;
+ }
+
+ if (kref_get_unless_zero(&zhdr->refcount) == 0) {
+ zhdr = NULL;
+ break;
+ }
+ if (!z3fold_page_trylock(zhdr)) {
+ if (kref_put(&zhdr->refcount,
+ release_z3fold_page))
+ atomic64_dec(&pool->pages_nr);
+ zhdr = NULL;
+ continue; /* can't evict at this point */
+ }
+
+ /* test_and_set_bit is of course atomic, but we still
+ * need to do it under page lock, otherwise checking
+ * that bit in __z3fold_alloc wouldn't make sense
+ */
+ if (zhdr->foreign_handles ||
+ test_and_set_bit(PAGE_CLAIMED, &page->private)) {
+ if (kref_put(&zhdr->refcount,
+ release_z3fold_page_locked))
+ atomic64_dec(&pool->pages_nr);
+ else
+ z3fold_page_unlock(zhdr);
+ zhdr = NULL;
+ continue; /* can't evict such page */
+ }
+ 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, and
+ * use our local slots structure because z3fold_free
+ * can zero out zhdr->slots and we can't do much
+ * about that
+ */
+ first_handle = 0;
+ last_handle = 0;
+ middle_handle = 0;
+ memset(slots.slot, 0, sizeof(slots.slot));
+ if (zhdr->first_chunks)
+ first_handle = __encode_handle(zhdr, &slots,
+ FIRST);
+ if (zhdr->middle_chunks)
+ middle_handle = __encode_handle(zhdr, &slots,
+ MIDDLE);
+ if (zhdr->last_chunks)
+ last_handle = __encode_handle(zhdr, &slots,
+ 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, true);
+ atomic64_dec(&pool->pages_nr);
+ return 0;
+ }
+ spin_lock(&pool->lock);
+ list_add(&page->lru, &pool->lru);
+ spin_unlock(&pool->lock);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ } else {
+ struct z3fold_buddy_slots *slots = zhdr->slots;
+ z3fold_page_lock(zhdr);
+ if (kref_put(&zhdr->refcount,
+ release_z3fold_page_locked)) {
+ kmem_cache_free(pool->c_handle, slots);
+ 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);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ }
+
+ /* 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 = get_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 - (handle_to_chunks(handle) << CHUNK_SHIFT);
+ break;
+ default:
+ pr_err("unknown buddy id %d\n", buddy);
+ WARN_ON(1);
+ addr = NULL;
+ break;
+ }
+
+ if (addr)
+ zhdr->mapped_count++;
+out:
+ put_z3fold_header(zhdr);
+ 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 = get_z3fold_header(handle);
+ page = virt_to_page(zhdr);
+
+ if (test_bit(PAGE_HEADLESS, &page->private))
+ return;
+
+ buddy = handle_to_buddy(handle);
+ if (buddy == MIDDLE)
+ clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
+ zhdr->mapped_count--;
+ put_z3fold_header(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);
+}
+
+static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
+{
+ struct z3fold_header *zhdr;
+ struct z3fold_pool *pool;
+
+ VM_BUG_ON_PAGE(!PageMovable(page), page);
+ VM_BUG_ON_PAGE(PageIsolated(page), page);
+
+ if (test_bit(PAGE_HEADLESS, &page->private))
+ return false;
+
+ zhdr = page_address(page);
+ z3fold_page_lock(zhdr);
+ if (test_bit(NEEDS_COMPACTING, &page->private) ||
+ test_bit(PAGE_STALE, &page->private))
+ goto out;
+
+ if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
+ goto out;
+
+ if (test_and_set_bit(PAGE_CLAIMED, &page->private))
+ goto out;
+ pool = zhdr_to_pool(zhdr);
+ spin_lock(&pool->lock);
+ if (!list_empty(&zhdr->buddy))
+ list_del_init(&zhdr->buddy);
+ if (!list_empty(&page->lru))
+ list_del_init(&page->lru);
+ spin_unlock(&pool->lock);
+
+ kref_get(&zhdr->refcount);
+ z3fold_page_unlock(zhdr);
+ return true;
+
+out:
+ z3fold_page_unlock(zhdr);
+ return false;
+}
+
+static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
+ struct page *page, enum migrate_mode mode)
+{
+ struct z3fold_header *zhdr, *new_zhdr;
+ struct z3fold_pool *pool;
+ struct address_space *new_mapping;
+
+ VM_BUG_ON_PAGE(!PageMovable(page), page);
+ VM_BUG_ON_PAGE(!PageIsolated(page), page);
+ VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), page);
+ VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
+
+ zhdr = page_address(page);
+ pool = zhdr_to_pool(zhdr);
+
+ if (!z3fold_page_trylock(zhdr))
+ return -EAGAIN;
+ if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
+ z3fold_page_unlock(zhdr);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ return -EBUSY;
+ }
+ if (work_pending(&zhdr->work)) {
+ z3fold_page_unlock(zhdr);
+ return -EAGAIN;
+ }
+ new_zhdr = page_address(newpage);
+ memcpy(new_zhdr, zhdr, PAGE_SIZE);
+ newpage->private = page->private;
+ page->private = 0;
+ z3fold_page_unlock(zhdr);
+ spin_lock_init(&new_zhdr->page_lock);
+ INIT_WORK(&new_zhdr->work, compact_page_work);
+ /*
+ * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
+ * so we only have to reinitialize it.
+ */
+ INIT_LIST_HEAD(&new_zhdr->buddy);
+ new_mapping = page_mapping(page);
+ __ClearPageMovable(page);
+ ClearPagePrivate(page);
+
+ get_page(newpage);
+ z3fold_page_lock(new_zhdr);
+ if (new_zhdr->first_chunks)
+ encode_handle(new_zhdr, FIRST);
+ if (new_zhdr->last_chunks)
+ encode_handle(new_zhdr, LAST);
+ if (new_zhdr->middle_chunks)
+ encode_handle(new_zhdr, MIDDLE);
+ set_bit(NEEDS_COMPACTING, &newpage->private);
+ new_zhdr->cpu = smp_processor_id();
+ spin_lock(&pool->lock);
+ list_add(&newpage->lru, &pool->lru);
+ spin_unlock(&pool->lock);
+ __SetPageMovable(newpage, new_mapping);
+ z3fold_page_unlock(new_zhdr);
+
+ queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
+
+ page_mapcount_reset(page);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ put_page(page);
+ return 0;
+}
+
+static void z3fold_page_putback(struct page *page)
+{
+ struct z3fold_header *zhdr;
+ struct z3fold_pool *pool;
+
+ zhdr = page_address(page);
+ pool = zhdr_to_pool(zhdr);
+
+ z3fold_page_lock(zhdr);
+ if (!list_empty(&zhdr->buddy))
+ list_del_init(&zhdr->buddy);
+ INIT_LIST_HEAD(&page->lru);
+ if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
+ atomic64_dec(&pool->pages_nr);
+ return;
+ }
+ spin_lock(&pool->lock);
+ list_add(&page->lru, &pool->lru);
+ spin_unlock(&pool->lock);
+ clear_bit(PAGE_CLAIMED, &page->private);
+ z3fold_page_unlock(zhdr);
+}
+
+static const struct address_space_operations z3fold_aops = {
+ .isolate_page = z3fold_page_isolate,
+ .migratepage = z3fold_page_migrate,
+ .putback_page = z3fold_page_putback,
+};
+
+/*****************
+ * 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)
+{
+ int ret;
+
+ /* Make sure the z3fold header is not larger than the page size */
+ BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
+ ret = z3fold_mount();
+ if (ret)
+ return ret;
+
+ zpool_register_driver(&z3fold_zpool_driver);
+
+ return 0;
+}
+
+static void __exit exit_z3fold(void)
+{
+ z3fold_unmount();
+ 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");