| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Vitaly Wool | 4470 | 99.36% | 15 | 78.95% |
| Xidong Wang | 23 | 0.51% | 1 | 5.26% |
| Matthew Wilcox | 3 | 0.07% | 1 | 5.26% |
| zhong jiang | 2 | 0.04% | 1 | 5.26% |
| Mike Rapoport | 1 | 0.02% | 1 | 5.26% |
| Total | 4499 | 19 |
/* * 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");
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