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Diffstat (limited to 'mm/z3fold.c')
| -rw-r--r-- | mm/z3fold.c | 1153 |
1 files changed, 1153 insertions, 0 deletions
diff --git a/mm/z3fold.c b/mm/z3fold.c new file mode 100644 index 000000000..aee9b0b8d --- /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"); |