/* * zsmalloc memory allocator * * Copyright (C) 2011 Nitin Gupta * Copyright (C) 2012, 2013 Minchan Kim * * This code is released using a dual license strategy: BSD/GPL * You can choose the license that better fits your requirements. * * Released under the terms of 3-clause BSD License * Released under the terms of GNU General Public License Version 2.0 */ /* * This allocator is designed for use with zram. Thus, the allocator is * supposed to work well under low memory conditions. In particular, it * never attempts higher order page allocation which is very likely to * fail under memory pressure. On the other hand, if we just use single * (0-order) pages, it would suffer from very high fragmentation -- * any object of size PAGE_SIZE/2 or larger would occupy an entire page. * This was one of the major issues with its predecessor (xvmalloc). * * To overcome these issues, zsmalloc allocates a bunch of 0-order pages * and links them together using various 'struct page' fields. These linked * pages act as a single higher-order page i.e. an object can span 0-order * page boundaries. The code refers to these linked pages as a single entity * called zspage. * * For simplicity, zsmalloc can only allocate objects of size up to PAGE_SIZE * since this satisfies the requirements of all its current users (in the * worst case, page is incompressible and is thus stored "as-is" i.e. in * uncompressed form). For allocation requests larger than this size, failure * is returned (see zs_malloc). * * Additionally, zs_malloc() does not return a dereferenceable pointer. * Instead, it returns an opaque handle (unsigned long) which encodes actual * location of the allocated object. The reason for this indirection is that * zsmalloc does not keep zspages permanently mapped since that would cause * issues on 32-bit systems where the VA region for kernel space mappings * is very small. So, before using the allocating memory, the object has to * be mapped using zs_map_object() to get a usable pointer and subsequently * unmapped using zs_unmap_object(). * * Following is how we use various fields and flags of underlying * struct page(s) to form a zspage. * * Usage of struct page fields: * page->first_page: points to the first component (0-order) page * page->index (union with page->freelist): offset of the first object * starting in this page. For the first page, this is * always 0, so we use this field (aka freelist) to point * to the first free object in zspage. * page->lru: links together all component pages (except the first page) * of a zspage * * For _first_ page only: * * page->private (union with page->first_page): refers to the * component page after the first page * If the page is first_page for huge object, it stores handle. * Look at size_class->huge. * page->freelist: points to the first free object in zspage. * Free objects are linked together using in-place * metadata. * page->objects: maximum number of objects we can store in this * zspage (class->zspage_order * PAGE_SIZE / class->size) * page->lru: links together first pages of various zspages. * Basically forming list of zspages in a fullness group. * page->mapping: class index and fullness group of the zspage * * Usage of struct page flags: * PG_private: identifies the first component page * PG_private2: identifies the last component page * */ #ifdef CONFIG_ZSMALLOC_DEBUG #define DEBUG #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * This must be power of 2 and greater than of equal to sizeof(link_free). * These two conditions ensure that any 'struct link_free' itself doesn't * span more than 1 page which avoids complex case of mapping 2 pages simply * to restore link_free pointer values. */ #define ZS_ALIGN 8 /* * A single 'zspage' is composed of up to 2^N discontiguous 0-order (single) * pages. ZS_MAX_ZSPAGE_ORDER defines upper limit on N. */ #define ZS_MAX_ZSPAGE_ORDER 2 #define ZS_MAX_PAGES_PER_ZSPAGE (_AC(1, UL) << ZS_MAX_ZSPAGE_ORDER) #define ZS_HANDLE_SIZE (sizeof(unsigned long)) /* * Object location (, ) is encoded as * as single (unsigned long) handle value. * * Note that object index is relative to system * page it is stored in, so for each sub-page belonging * to a zspage, obj_idx starts with 0. * * This is made more complicated by various memory models and PAE. */ #ifndef MAX_PHYSMEM_BITS #ifdef CONFIG_HIGHMEM64G #define MAX_PHYSMEM_BITS 36 #else /* !CONFIG_HIGHMEM64G */ /* * If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just * be PAGE_SHIFT */ #define MAX_PHYSMEM_BITS BITS_PER_LONG #endif #endif #define _PFN_BITS (MAX_PHYSMEM_BITS - PAGE_SHIFT) /* * Memory for allocating for handle keeps object position by * encoding and the encoded value has a room * in least bit(ie, look at obj_to_location). * We use the bit to synchronize between object access by * user and migration. */ #define HANDLE_PIN_BIT 0 /* * Head in allocated object should have OBJ_ALLOCATED_TAG * to identify the object was allocated or not. * It's okay to add the status bit in the least bit because * header keeps handle which is 4byte-aligned address so we * have room for two bit at least. */ #define OBJ_ALLOCATED_TAG 1 #define OBJ_TAG_BITS 1 #define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS) #define OBJ_INDEX_MASK ((_AC(1, UL) << OBJ_INDEX_BITS) - 1) #define MAX(a, b) ((a) >= (b) ? (a) : (b)) /* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */ #define ZS_MIN_ALLOC_SIZE \ MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS)) /* each chunk includes extra space to keep handle */ #define ZS_MAX_ALLOC_SIZE PAGE_SIZE /* * On systems with 4K page size, this gives 255 size classes! There is a * trader-off here: * - Large number of size classes is potentially wasteful as free page are * spread across these classes * - Small number of size classes causes large internal fragmentation * - Probably its better to use specific size classes (empirically * determined). NOTE: all those class sizes must be set as multiple of * ZS_ALIGN to make sure link_free itself never has to span 2 pages. * * ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN * (reason above) */ #define ZS_SIZE_CLASS_DELTA (PAGE_SIZE >> 8) /* * We do not maintain any list for completely empty or full pages */ enum fullness_group { ZS_ALMOST_FULL, ZS_ALMOST_EMPTY, _ZS_NR_FULLNESS_GROUPS, ZS_EMPTY, ZS_FULL }; enum zs_stat_type { OBJ_ALLOCATED, OBJ_USED, CLASS_ALMOST_FULL, CLASS_ALMOST_EMPTY, NR_ZS_STAT_TYPE, }; #ifdef CONFIG_ZSMALLOC_STAT static struct dentry *zs_stat_root; struct zs_size_stat { unsigned long objs[NR_ZS_STAT_TYPE]; }; #endif /* * number of size_classes */ static int zs_size_classes; /* * We assign a page to ZS_ALMOST_EMPTY fullness group when: * n <= N / f, where * n = number of allocated objects * N = total number of objects zspage can store * f = fullness_threshold_frac * * Similarly, we assign zspage to: * ZS_ALMOST_FULL when n > N / f * ZS_EMPTY when n == 0 * ZS_FULL when n == N * * (see: fix_fullness_group()) */ static const int fullness_threshold_frac = 4; struct size_class { /* * Size of objects stored in this class. Must be multiple * of ZS_ALIGN. */ int size; unsigned int index; /* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */ int pages_per_zspage; /* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */ bool huge; #ifdef CONFIG_ZSMALLOC_STAT struct zs_size_stat stats; #endif spinlock_t lock; struct page *fullness_list[_ZS_NR_FULLNESS_GROUPS]; }; /* * Placed within free objects to form a singly linked list. * For every zspage, first_page->freelist gives head of this list. * * This must be power of 2 and less than or equal to ZS_ALIGN */ struct link_free { union { /* * Position of next free chunk (encodes ) * It's valid for non-allocated object */ void *next; /* * Handle of allocated object. */ unsigned long handle; }; }; struct zs_pool { char *name; struct size_class **size_class; struct kmem_cache *handle_cachep; gfp_t flags; /* allocation flags used when growing pool */ atomic_long_t pages_allocated; #ifdef CONFIG_ZSMALLOC_STAT struct dentry *stat_dentry; #endif }; /* * A zspage's class index and fullness group * are encoded in its (first)page->mapping */ #define CLASS_IDX_BITS 28 #define FULLNESS_BITS 4 #define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1) #define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1) struct mapping_area { #ifdef CONFIG_PGTABLE_MAPPING struct vm_struct *vm; /* vm area for mapping object that span pages */ #else char *vm_buf; /* copy buffer for objects that span pages */ #endif char *vm_addr; /* address of kmap_atomic()'ed pages */ enum zs_mapmode vm_mm; /* mapping mode */ bool huge; }; static int create_handle_cache(struct zs_pool *pool) { pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE, 0, 0, NULL); return pool->handle_cachep ? 0 : 1; } static void destroy_handle_cache(struct zs_pool *pool) { kmem_cache_destroy(pool->handle_cachep); } static unsigned long alloc_handle(struct zs_pool *pool) { return (unsigned long)kmem_cache_alloc(pool->handle_cachep, pool->flags & ~__GFP_HIGHMEM); } static void free_handle(struct zs_pool *pool, unsigned long handle) { kmem_cache_free(pool->handle_cachep, (void *)handle); } static void record_obj(unsigned long handle, unsigned long obj) { *(unsigned long *)handle = obj; } /* zpool driver */ #ifdef CONFIG_ZPOOL static void *zs_zpool_create(char *name, gfp_t gfp, struct zpool_ops *zpool_ops) { return zs_create_pool(name, gfp); } static void zs_zpool_destroy(void *pool) { zs_destroy_pool(pool); } static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp, unsigned long *handle) { *handle = zs_malloc(pool, size); return *handle ? 0 : -1; } static void zs_zpool_free(void *pool, unsigned long handle) { zs_free(pool, handle); } static int zs_zpool_shrink(void *pool, unsigned int pages, unsigned int *reclaimed) { return -EINVAL; } static void *zs_zpool_map(void *pool, unsigned long handle, enum zpool_mapmode mm) { enum zs_mapmode zs_mm; switch (mm) { case ZPOOL_MM_RO: zs_mm = ZS_MM_RO; break; case ZPOOL_MM_WO: zs_mm = ZS_MM_WO; break; case ZPOOL_MM_RW: /* fallthru */ default: zs_mm = ZS_MM_RW; break; } return zs_map_object(pool, handle, zs_mm); } static void zs_zpool_unmap(void *pool, unsigned long handle) { zs_unmap_object(pool, handle); } static u64 zs_zpool_total_size(void *pool) { return zs_get_total_pages(pool) << PAGE_SHIFT; } static struct zpool_driver zs_zpool_driver = { .type = "zsmalloc", .owner = THIS_MODULE, .create = zs_zpool_create, .destroy = zs_zpool_destroy, .malloc = zs_zpool_malloc, .free = zs_zpool_free, .shrink = zs_zpool_shrink, .map = zs_zpool_map, .unmap = zs_zpool_unmap, .total_size = zs_zpool_total_size, }; MODULE_ALIAS("zpool-zsmalloc"); #endif /* CONFIG_ZPOOL */ static unsigned int get_maxobj_per_zspage(int size, int pages_per_zspage) { return pages_per_zspage * PAGE_SIZE / size; } /* per-cpu VM mapping areas for zspage accesses that cross page boundaries */ static DEFINE_PER_CPU(struct mapping_area, zs_map_area); static int is_first_page(struct page *page) { return PagePrivate(page); } static int is_last_page(struct page *page) { return PagePrivate2(page); } static void get_zspage_mapping(struct page *page, unsigned int *class_idx, enum fullness_group *fullness) { unsigned long m; BUG_ON(!is_first_page(page)); m = (unsigned long)page->mapping; *fullness = m & FULLNESS_MASK; *class_idx = (m >> FULLNESS_BITS) & CLASS_IDX_MASK; } static void set_zspage_mapping(struct page *page, unsigned int class_idx, enum fullness_group fullness) { unsigned long m; BUG_ON(!is_first_page(page)); m = ((class_idx & CLASS_IDX_MASK) << FULLNESS_BITS) | (fullness & FULLNESS_MASK); page->mapping = (struct address_space *)m; } /* * zsmalloc divides the pool into various size classes where each * class maintains a list of zspages where each zspage is divided * into equal sized chunks. Each allocation falls into one of these * classes depending on its size. This function returns index of the * size class which has chunk size big enough to hold the give size. */ static int get_size_class_index(int size) { int idx = 0; if (likely(size > ZS_MIN_ALLOC_SIZE)) idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE, ZS_SIZE_CLASS_DELTA); return min(zs_size_classes - 1, idx); } #ifdef CONFIG_ZSMALLOC_STAT static inline void zs_stat_inc(struct size_class *class, enum zs_stat_type type, unsigned long cnt) { class->stats.objs[type] += cnt; } static inline void zs_stat_dec(struct size_class *class, enum zs_stat_type type, unsigned long cnt) { class->stats.objs[type] -= cnt; } static inline unsigned long zs_stat_get(struct size_class *class, enum zs_stat_type type) { return class->stats.objs[type]; } static int __init zs_stat_init(void) { if (!debugfs_initialized()) return -ENODEV; zs_stat_root = debugfs_create_dir("zsmalloc", NULL); if (!zs_stat_root) return -ENOMEM; return 0; } static void __exit zs_stat_exit(void) { debugfs_remove_recursive(zs_stat_root); } static int zs_stats_size_show(struct seq_file *s, void *v) { int i; struct zs_pool *pool = s->private; struct size_class *class; int objs_per_zspage; unsigned long class_almost_full, class_almost_empty; unsigned long obj_allocated, obj_used, pages_used; unsigned long total_class_almost_full = 0, total_class_almost_empty = 0; unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0; seq_printf(s, " %5s %5s %11s %12s %13s %10s %10s %16s\n", "class", "size", "almost_full", "almost_empty", "obj_allocated", "obj_used", "pages_used", "pages_per_zspage"); for (i = 0; i < zs_size_classes; i++) { class = pool->size_class[i]; if (class->index != i) continue; spin_lock(&class->lock); class_almost_full = zs_stat_get(class, CLASS_ALMOST_FULL); class_almost_empty = zs_stat_get(class, CLASS_ALMOST_EMPTY); obj_allocated = zs_stat_get(class, OBJ_ALLOCATED); obj_used = zs_stat_get(class, OBJ_USED); spin_unlock(&class->lock); objs_per_zspage = get_maxobj_per_zspage(class->size, class->pages_per_zspage); pages_used = obj_allocated / objs_per_zspage * class->pages_per_zspage; seq_printf(s, " %5u %5u %11lu %12lu %13lu %10lu %10lu %16d\n", i, class->size, class_almost_full, class_almost_empty, obj_allocated, obj_used, pages_used, class->pages_per_zspage); total_class_almost_full += class_almost_full; total_class_almost_empty += class_almost_empty; total_objs += obj_allocated; total_used_objs += obj_used; total_pages += pages_used; } seq_puts(s, "\n"); seq_printf(s, " %5s %5s %11lu %12lu %13lu %10lu %10lu\n", "Total", "", total_class_almost_full, total_class_almost_empty, total_objs, total_used_objs, total_pages); return 0; } static int zs_stats_size_open(struct inode *inode, struct file *file) { return single_open(file, zs_stats_size_show, inode->i_private); } static const struct file_operations zs_stat_size_ops = { .open = zs_stats_size_open, .read = seq_read, .llseek = seq_lseek, .release = single_release, }; static int zs_pool_stat_create(char *name, struct zs_pool *pool) { struct dentry *entry; if (!zs_stat_root) return -ENODEV; entry = debugfs_create_dir(name, zs_stat_root); if (!entry) { pr_warn("debugfs dir <%s> creation failed\n", name); return -ENOMEM; } pool->stat_dentry = entry; entry = debugfs_create_file("classes", S_IFREG | S_IRUGO, pool->stat_dentry, pool, &zs_stat_size_ops); if (!entry) { pr_warn("%s: debugfs file entry <%s> creation failed\n", name, "classes"); return -ENOMEM; } return 0; } static void zs_pool_stat_destroy(struct zs_pool *pool) { debugfs_remove_recursive(pool->stat_dentry); } #else /* CONFIG_ZSMALLOC_STAT */ static inline void zs_stat_inc(struct size_class *class, enum zs_stat_type type, unsigned long cnt) { } static inline void zs_stat_dec(struct size_class *class, enum zs_stat_type type, unsigned long cnt) { } static inline unsigned long zs_stat_get(struct size_class *class, enum zs_stat_type type) { return 0; } static int __init zs_stat_init(void) { return 0; } static void __exit zs_stat_exit(void) { } static inline int zs_pool_stat_create(char *name, struct zs_pool *pool) { return 0; } static inline void zs_pool_stat_destroy(struct zs_pool *pool) { } #endif /* * For each size class, zspages are divided into different groups * depending on how "full" they are. This was done so that we could * easily find empty or nearly empty zspages when we try to shrink * the pool (not yet implemented). This function returns fullness * status of the given page. */ static enum fullness_group get_fullness_group(struct page *page) { int inuse, max_objects; enum fullness_group fg; BUG_ON(!is_first_page(page)); inuse = page->inuse; max_objects = page->objects; if (inuse == 0) fg = ZS_EMPTY; else if (inuse == max_objects) fg = ZS_FULL; else if (inuse <= 3 * max_objects / fullness_threshold_frac) fg = ZS_ALMOST_EMPTY; else fg = ZS_ALMOST_FULL; return fg; } /* * Each size class maintains various freelists and zspages are assigned * to one of these freelists based on the number of live objects they * have. This functions inserts the given zspage into the freelist * identified by . */ static void insert_zspage(struct page *page, struct size_class *class, enum fullness_group fullness) { struct page **head; BUG_ON(!is_first_page(page)); if (fullness >= _ZS_NR_FULLNESS_GROUPS) return; head = &class->fullness_list[fullness]; if (*head) list_add_tail(&page->lru, &(*head)->lru); *head = page; zs_stat_inc(class, fullness == ZS_ALMOST_EMPTY ? CLASS_ALMOST_EMPTY : CLASS_ALMOST_FULL, 1); } /* * This function removes the given zspage from the freelist identified * by . */ static void remove_zspage(struct page *page, struct size_class *class, enum fullness_group fullness) { struct page **head; BUG_ON(!is_first_page(page)); if (fullness >= _ZS_NR_FULLNESS_GROUPS) return; head = &class->fullness_list[fullness]; BUG_ON(!*head); if (list_empty(&(*head)->lru)) *head = NULL; else if (*head == page) *head = (struct page *)list_entry((*head)->lru.next, struct page, lru); list_del_init(&page->lru); zs_stat_dec(class, fullness == ZS_ALMOST_EMPTY ? CLASS_ALMOST_EMPTY : CLASS_ALMOST_FULL, 1); } /* * Each size class maintains zspages in different fullness groups depending * on the number of live objects they contain. When allocating or freeing * objects, the fullness status of the page can change, say, from ALMOST_FULL * to ALMOST_EMPTY when freeing an object. This function checks if such * a status change has occurred for the given page and accordingly moves the * page from the freelist of the old fullness group to that of the new * fullness group. */ static enum fullness_group fix_fullness_group(struct size_class *class, struct page *page) { int class_idx; enum fullness_group currfg, newfg; BUG_ON(!is_first_page(page)); get_zspage_mapping(page, &class_idx, &currfg); newfg = get_fullness_group(page); if (newfg == currfg) goto out; remove_zspage(page, class, currfg); insert_zspage(page, class, newfg); set_zspage_mapping(page, class_idx, newfg); out: return newfg; } /* * We have to decide on how many pages to link together * to form a zspage for each size class. This is important * to reduce wastage due to unusable space left at end of * each zspage which is given as: * wastage = Zp - Zp % size_class * where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ... * * For example, for size class of 3/8 * PAGE_SIZE, we should * link together 3 PAGE_SIZE sized pages to form a zspage * since then we can perfectly fit in 8 such objects. */ static int get_pages_per_zspage(int class_size) { int i, max_usedpc = 0; /* zspage order which gives maximum used size per KB */ int max_usedpc_order = 1; for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) { int zspage_size; int waste, usedpc; zspage_size = i * PAGE_SIZE; waste = zspage_size % class_size; usedpc = (zspage_size - waste) * 100 / zspage_size; if (usedpc > max_usedpc) { max_usedpc = usedpc; max_usedpc_order = i; } } return max_usedpc_order; } /* * A single 'zspage' is composed of many system pages which are * linked together using fields in struct page. This function finds * the first/head page, given any component page of a zspage. */ static struct page *get_first_page(struct page *page) { if (is_first_page(page)) return page; else return page->first_page; } static struct page *get_next_page(struct page *page) { struct page *next; if (is_last_page(page)) next = NULL; else if (is_first_page(page)) next = (struct page *)page_private(page); else next = list_entry(page->lru.next, struct page, lru); return next; } /* * Encode as a single handle value. * We use the least bit of handle for tagging. */ static void *location_to_obj(struct page *page, unsigned long obj_idx) { unsigned long obj; if (!page) { BUG_ON(obj_idx); return NULL; } obj = page_to_pfn(page) << OBJ_INDEX_BITS; obj |= ((obj_idx) & OBJ_INDEX_MASK); obj <<= OBJ_TAG_BITS; return (void *)obj; } /* * Decode pair from the given object handle. We adjust the * decoded obj_idx back to its original value since it was adjusted in * location_to_obj(). */ static void obj_to_location(unsigned long obj, struct page **page, unsigned long *obj_idx) { obj >>= OBJ_TAG_BITS; *page = pfn_to_page(obj >> OBJ_INDEX_BITS); *obj_idx = (obj & OBJ_INDEX_MASK); } static unsigned long handle_to_obj(unsigned long handle) { return *(unsigned long *)handle; } static unsigned long obj_to_head(struct size_class *class, struct page *page, void *obj) { if (class->huge) { VM_BUG_ON(!is_first_page(page)); return *(unsigned long *)page_private(page); } else return *(unsigned long *)obj; } static unsigned long obj_idx_to_offset(struct page *page, unsigned long obj_idx, int class_size) { unsigned long off = 0; if (!is_first_page(page)) off = page->index; return off + obj_idx * class_size; } static inline int trypin_tag(unsigned long handle) { unsigned long *ptr = (unsigned long *)handle; return !test_and_set_bit_lock(HANDLE_PIN_BIT, ptr); } static void pin_tag(unsigned long handle) { while (!trypin_tag(handle)); } static void unpin_tag(unsigned long handle) { unsigned long *ptr = (unsigned long *)handle; clear_bit_unlock(HANDLE_PIN_BIT, ptr); } static void reset_page(struct page *page) { clear_bit(PG_private, &page->flags); clear_bit(PG_private_2, &page->flags); set_page_private(page, 0); page->mapping = NULL; page->freelist = NULL; page_mapcount_reset(page); } static void free_zspage(struct page *first_page) { struct page *nextp, *tmp, *head_extra; BUG_ON(!is_first_page(first_page)); BUG_ON(first_page->inuse); head_extra = (struct page *)page_private(first_page); reset_page(first_page); __free_page(first_page); /* zspage with only 1 system page */ if (!head_extra) return; list_for_each_entry_safe(nextp, tmp, &head_extra->lru, lru) { list_del(&nextp->lru); reset_page(nextp); __free_page(nextp); } reset_page(head_extra); __free_page(head_extra); } /* Initialize a newly allocated zspage */ static void init_zspage(struct page *first_page, struct size_class *class) { unsigned long off = 0; struct page *page = first_page; BUG_ON(!is_first_page(first_page)); while (page) { struct page *next_page; struct link_free *link; unsigned int i = 1; void *vaddr; /* * page->index stores offset of first object starting * in the page. For the first page, this is always 0, * so we use first_page->index (aka ->freelist) to store * head of corresponding zspage's freelist. */ if (page != first_page) page->index = off; vaddr = kmap_atomic(page); link = (struct link_free *)vaddr + off / sizeof(*link); while ((off += class->size) < PAGE_SIZE) { link->next = location_to_obj(page, i++); link += class->size / sizeof(*link); } /* * We now come to the last (full or partial) object on this * page, which must point to the first object on the next * page (if present) */ next_page = get_next_page(page); link->next = location_to_obj(next_page, 0); kunmap_atomic(vaddr); page = next_page; off %= PAGE_SIZE; } } /* * Allocate a zspage for the given size class */ static struct page *alloc_zspage(struct size_class *class, gfp_t flags) { int i, error; struct page *first_page = NULL, *uninitialized_var(prev_page); /* * Allocate individual pages and link them together as: * 1. first page->private = first sub-page * 2. all sub-pages are linked together using page->lru * 3. each sub-page is linked to the first page using page->first_page * * For each size class, First/Head pages are linked together using * page->lru. Also, we set PG_private to identify the first page * (i.e. no other sub-page has this flag set) and PG_private_2 to * identify the last page. */ error = -ENOMEM; for (i = 0; i < class->pages_per_zspage; i++) { struct page *page; page = alloc_page(flags); if (!page) goto cleanup; INIT_LIST_HEAD(&page->lru); if (i == 0) { /* first page */ SetPagePrivate(page); set_page_private(page, 0); first_page = page; first_page->inuse = 0; } if (i == 1) set_page_private(first_page, (unsigned long)page); if (i >= 1) page->first_page = first_page; if (i >= 2) list_add(&page->lru, &prev_page->lru); if (i == class->pages_per_zspage - 1) /* last page */ SetPagePrivate2(page); prev_page = page; } init_zspage(first_page, class); first_page->freelist = location_to_obj(first_page, 0); /* Maximum number of objects we can store in this zspage */ first_page->objects = class->pages_per_zspage * PAGE_SIZE / class->size; error = 0; /* Success */ cleanup: if (unlikely(error) && first_page) { free_zspage(first_page); first_page = NULL; } return first_page; } static struct page *find_get_zspage(struct size_class *class) { int i; struct page *page; for (i = 0; i < _ZS_NR_FULLNESS_GROUPS; i++) { page = class->fullness_list[i]; if (page) break; } return page; } #ifdef CONFIG_PGTABLE_MAPPING static inline int __zs_cpu_up(struct mapping_area *area) { /* * Make sure we don't leak memory if a cpu UP notification * and zs_init() race and both call zs_cpu_up() on the same cpu */ if (area->vm) return 0; area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL); if (!area->vm) return -ENOMEM; return 0; } static inline void __zs_cpu_down(struct mapping_area *area) { if (area->vm) free_vm_area(area->vm); area->vm = NULL; } static inline void *__zs_map_object(struct mapping_area *area, struct page *pages[2], int off, int size) { BUG_ON(map_vm_area(area->vm, PAGE_KERNEL, pages)); area->vm_addr = area->vm->addr; return area->vm_addr + off; } static inline void __zs_unmap_object(struct mapping_area *area, struct page *pages[2], int off, int size) { unsigned long addr = (unsigned long)area->vm_addr; unmap_kernel_range(addr, PAGE_SIZE * 2); } #else /* CONFIG_PGTABLE_MAPPING */ static inline int __zs_cpu_up(struct mapping_area *area) { /* * Make sure we don't leak memory if a cpu UP notification * and zs_init() race and both call zs_cpu_up() on the same cpu */ if (area->vm_buf) return 0; area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL); if (!area->vm_buf) return -ENOMEM; return 0; } static inline void __zs_cpu_down(struct mapping_area *area) { kfree(area->vm_buf); area->vm_buf = NULL; } static void *__zs_map_object(struct mapping_area *area, struct page *pages[2], int off, int size) { int sizes[2]; void *addr; char *buf = area->vm_buf; /* disable page faults to match kmap_atomic() return conditions */ pagefault_disable(); /* no read fastpath */ if (area->vm_mm == ZS_MM_WO) goto out; sizes[0] = PAGE_SIZE - off; sizes[1] = size - sizes[0]; /* copy object to per-cpu buffer */ addr = kmap_atomic(pages[0]); memcpy(buf, addr + off, sizes[0]); kunmap_atomic(addr); addr = kmap_atomic(pages[1]); memcpy(buf + sizes[0], addr, sizes[1]); kunmap_atomic(addr); out: return area->vm_buf; } static void __zs_unmap_object(struct mapping_area *area, struct page *pages[2], int off, int size) { int sizes[2]; void *addr; char *buf; /* no write fastpath */ if (area->vm_mm == ZS_MM_RO) goto out; buf = area->vm_buf; if (!area->huge) { buf = buf + ZS_HANDLE_SIZE; size -= ZS_HANDLE_SIZE; off += ZS_HANDLE_SIZE; } sizes[0] = PAGE_SIZE - off; sizes[1] = size - sizes[0]; /* copy per-cpu buffer to object */ addr = kmap_atomic(pages[0]); memcpy(addr + off, buf, sizes[0]); kunmap_atomic(addr); addr = kmap_atomic(pages[1]); memcpy(addr, buf + sizes[0], sizes[1]); kunmap_atomic(addr); out: /* enable page faults to match kunmap_atomic() return conditions */ pagefault_enable(); } #endif /* CONFIG_PGTABLE_MAPPING */ static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action, void *pcpu) { int ret, cpu = (long)pcpu; struct mapping_area *area; switch (action) { case CPU_UP_PREPARE: area = &per_cpu(zs_map_area, cpu); ret = __zs_cpu_up(area); if (ret) return notifier_from_errno(ret); break; case CPU_DEAD: case CPU_UP_CANCELED: area = &per_cpu(zs_map_area, cpu); __zs_cpu_down(area); break; } return NOTIFY_OK; } static struct notifier_block zs_cpu_nb = { .notifier_call = zs_cpu_notifier }; static int zs_register_cpu_notifier(void) { int cpu, uninitialized_var(ret); cpu_notifier_register_begin(); __register_cpu_notifier(&zs_cpu_nb); for_each_online_cpu(cpu) { ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu); if (notifier_to_errno(ret)) break; } cpu_notifier_register_done(); return notifier_to_errno(ret); } static void zs_unregister_cpu_notifier(void) { int cpu; cpu_notifier_register_begin(); for_each_online_cpu(cpu) zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu); __unregister_cpu_notifier(&zs_cpu_nb); cpu_notifier_register_done(); } static void init_zs_size_classes(void) { int nr; nr = (ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1; if ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) % ZS_SIZE_CLASS_DELTA) nr += 1; zs_size_classes = nr; } static bool can_merge(struct size_class *prev, int size, int pages_per_zspage) { if (prev->pages_per_zspage != pages_per_zspage) return false; if (get_maxobj_per_zspage(prev->size, prev->pages_per_zspage) != get_maxobj_per_zspage(size, pages_per_zspage)) return false; return true; } static bool zspage_full(struct page *page) { BUG_ON(!is_first_page(page)); return page->inuse == page->objects; } unsigned long zs_get_total_pages(struct zs_pool *pool) { return atomic_long_read(&pool->pages_allocated); } EXPORT_SYMBOL_GPL(zs_get_total_pages); /** * zs_map_object - get address of allocated object from handle. * @pool: pool from which the object was allocated * @handle: handle returned from zs_malloc * * Before using an object allocated from zs_malloc, it must be mapped using * this function. When done with the object, it must be unmapped using * zs_unmap_object. * * Only one object can be mapped per cpu at a time. There is no protection * against nested mappings. * * This function returns with preemption and page faults disabled. */ void *zs_map_object(struct zs_pool *pool, unsigned long handle, enum zs_mapmode mm) { struct page *page; unsigned long obj, obj_idx, off; unsigned int class_idx; enum fullness_group fg; struct size_class *class; struct mapping_area *area; struct page *pages[2]; void *ret; BUG_ON(!handle); /* * Because we use per-cpu mapping areas shared among the * pools/users, we can't allow mapping in interrupt context * because it can corrupt another users mappings. */ BUG_ON(in_interrupt()); /* From now on, migration cannot move the object */ pin_tag(handle); obj = handle_to_obj(handle); obj_to_location(obj, &page, &obj_idx); get_zspage_mapping(get_first_page(page), &class_idx, &fg); class = pool->size_class[class_idx]; off = obj_idx_to_offset(page, obj_idx, class->size); area = &get_cpu_var(zs_map_area); area->vm_mm = mm; if (off + class->size <= PAGE_SIZE) { /* this object is contained entirely within a page */ area->vm_addr = kmap_atomic(page); ret = area->vm_addr + off; goto out; } /* this object spans two pages */ pages[0] = page; pages[1] = get_next_page(page); BUG_ON(!pages[1]); ret = __zs_map_object(area, pages, off, class->size); out: if (!class->huge) ret += ZS_HANDLE_SIZE; return ret; } EXPORT_SYMBOL_GPL(zs_map_object); void zs_unmap_object(struct zs_pool *pool, unsigned long handle) { struct page *page; unsigned long obj, obj_idx, off; unsigned int class_idx; enum fullness_group fg; struct size_class *class; struct mapping_area *area; BUG_ON(!handle); obj = handle_to_obj(handle); obj_to_location(obj, &page, &obj_idx); get_zspage_mapping(get_first_page(page), &class_idx, &fg); class = pool->size_class[class_idx]; off = obj_idx_to_offset(page, obj_idx, class->size); area = this_cpu_ptr(&zs_map_area); if (off + class->size <= PAGE_SIZE) kunmap_atomic(area->vm_addr); else { struct page *pages[2]; pages[0] = page; pages[1] = get_next_page(page); BUG_ON(!pages[1]); __zs_unmap_object(area, pages, off, class->size); } put_cpu_var(zs_map_area); unpin_tag(handle); } EXPORT_SYMBOL_GPL(zs_unmap_object); static unsigned long obj_malloc(struct page *first_page, struct size_class *class, unsigned long handle) { unsigned long obj; struct link_free *link; struct page *m_page; unsigned long m_objidx, m_offset; void *vaddr; handle |= OBJ_ALLOCATED_TAG; obj = (unsigned long)first_page->freelist; obj_to_location(obj, &m_page, &m_objidx); m_offset = obj_idx_to_offset(m_page, m_objidx, class->size); vaddr = kmap_atomic(m_page); link = (struct link_free *)vaddr + m_offset / sizeof(*link); first_page->freelist = link->next; if (!class->huge) /* record handle in the header of allocated chunk */ link->handle = handle; else /* record handle in first_page->private */ set_page_private(first_page, handle); kunmap_atomic(vaddr); first_page->inuse++; zs_stat_inc(class, OBJ_USED, 1); return obj; } /** * zs_malloc - Allocate block of given size from pool. * @pool: pool to allocate from * @size: size of block to allocate * * On success, handle to the allocated object is returned, * otherwise 0. * Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail. */ unsigned long zs_malloc(struct zs_pool *pool, size_t size) { unsigned long handle, obj; struct size_class *class; struct page *first_page; if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE)) return 0; handle = alloc_handle(pool); if (!handle) return 0; /* extra space in chunk to keep the handle */ size += ZS_HANDLE_SIZE; class = pool->size_class[get_size_class_index(size)]; /* In huge class size, we store the handle into first_page->private */ if (class->huge) { size -= ZS_HANDLE_SIZE; class = pool->size_class[get_size_class_index(size)]; } spin_lock(&class->lock); first_page = find_get_zspage(class); if (!first_page) { spin_unlock(&class->lock); first_page = alloc_zspage(class, pool->flags); if (unlikely(!first_page)) { free_handle(pool, handle); return 0; } set_zspage_mapping(first_page, class->index, ZS_EMPTY); atomic_long_add(class->pages_per_zspage, &pool->pages_allocated); spin_lock(&class->lock); zs_stat_inc(class, OBJ_ALLOCATED, get_maxobj_per_zspage( class->size, class->pages_per_zspage)); } obj = obj_malloc(first_page, class, handle); /* Now move the zspage to another fullness group, if required */ fix_fullness_group(class, first_page); record_obj(handle, obj); spin_unlock(&class->lock); return handle; } EXPORT_SYMBOL_GPL(zs_malloc); static void obj_free(struct zs_pool *pool, struct size_class *class, unsigned long obj) { struct link_free *link; struct page *first_page, *f_page; unsigned long f_objidx, f_offset; void *vaddr; int class_idx; enum fullness_group fullness; BUG_ON(!obj); obj &= ~OBJ_ALLOCATED_TAG; obj_to_location(obj, &f_page, &f_objidx); first_page = get_first_page(f_page); get_zspage_mapping(first_page, &class_idx, &fullness); f_offset = obj_idx_to_offset(f_page, f_objidx, class->size); vaddr = kmap_atomic(f_page); /* Insert this object in containing zspage's freelist */ link = (struct link_free *)(vaddr + f_offset); link->next = first_page->freelist; if (class->huge) set_page_private(first_page, 0); kunmap_atomic(vaddr); first_page->freelist = (void *)obj; first_page->inuse--; zs_stat_dec(class, OBJ_USED, 1); } void zs_free(struct zs_pool *pool, unsigned long handle) { struct page *first_page, *f_page; unsigned long obj, f_objidx; int class_idx; struct size_class *class; enum fullness_group fullness; if (unlikely(!handle)) return; pin_tag(handle); obj = handle_to_obj(handle); obj_to_location(obj, &f_page, &f_objidx); first_page = get_first_page(f_page); get_zspage_mapping(first_page, &class_idx, &fullness); class = pool->size_class[class_idx]; spin_lock(&class->lock); obj_free(pool, class, obj); fullness = fix_fullness_group(class, first_page); if (fullness == ZS_EMPTY) { zs_stat_dec(class, OBJ_ALLOCATED, get_maxobj_per_zspage( class->size, class->pages_per_zspage)); atomic_long_sub(class->pages_per_zspage, &pool->pages_allocated); free_zspage(first_page); } spin_unlock(&class->lock); unpin_tag(handle); free_handle(pool, handle); } EXPORT_SYMBOL_GPL(zs_free); static void zs_object_copy(unsigned long src, unsigned long dst, struct size_class *class) { struct page *s_page, *d_page; unsigned long s_objidx, d_objidx; unsigned long s_off, d_off; void *s_addr, *d_addr; int s_size, d_size, size; int written = 0; s_size = d_size = class->size; obj_to_location(src, &s_page, &s_objidx); obj_to_location(dst, &d_page, &d_objidx); s_off = obj_idx_to_offset(s_page, s_objidx, class->size); d_off = obj_idx_to_offset(d_page, d_objidx, class->size); if (s_off + class->size > PAGE_SIZE) s_size = PAGE_SIZE - s_off; if (d_off + class->size > PAGE_SIZE) d_size = PAGE_SIZE - d_off; s_addr = kmap_atomic(s_page); d_addr = kmap_atomic(d_page); while (1) { size = min(s_size, d_size); memcpy(d_addr + d_off, s_addr + s_off, size); written += size; if (written == class->size) break; if (s_off + size >= PAGE_SIZE) { kunmap_atomic(d_addr); kunmap_atomic(s_addr); s_page = get_next_page(s_page); BUG_ON(!s_page); s_addr = kmap_atomic(s_page); d_addr = kmap_atomic(d_page); s_size = class->size - written; s_off = 0; } else { s_off += size; s_size -= size; } if (d_off + size >= PAGE_SIZE) { kunmap_atomic(d_addr); d_page = get_next_page(d_page); BUG_ON(!d_page); d_addr = kmap_atomic(d_page); d_size = class->size - written; d_off = 0; } else { d_off += size; d_size -= size; } } kunmap_atomic(d_addr); kunmap_atomic(s_addr); } /* * Find alloced object in zspage from index object and * return handle. */ static unsigned long find_alloced_obj(struct page *page, int index, struct size_class *class) { unsigned long head; int offset = 0; unsigned long handle = 0; void *addr = kmap_atomic(page); if (!is_first_page(page)) offset = page->index; offset += class->size * index; while (offset < PAGE_SIZE) { head = obj_to_head(class, page, addr + offset); if (head & OBJ_ALLOCATED_TAG) { handle = head & ~OBJ_ALLOCATED_TAG; if (trypin_tag(handle)) break; handle = 0; } offset += class->size; index++; } kunmap_atomic(addr); return handle; } struct zs_compact_control { /* Source page for migration which could be a subpage of zspage. */ struct page *s_page; /* Destination page for migration which should be a first page * of zspage. */ struct page *d_page; /* Starting object index within @s_page which used for live object * in the subpage. */ int index; /* how many of objects are migrated */ int nr_migrated; }; static int migrate_zspage(struct zs_pool *pool, struct size_class *class, struct zs_compact_control *cc) { unsigned long used_obj, free_obj; unsigned long handle; struct page *s_page = cc->s_page; struct page *d_page = cc->d_page; unsigned long index = cc->index; int nr_migrated = 0; int ret = 0; while (1) { handle = find_alloced_obj(s_page, index, class); if (!handle) { s_page = get_next_page(s_page); if (!s_page) break; index = 0; continue; } /* Stop if there is no more space */ if (zspage_full(d_page)) { unpin_tag(handle); ret = -ENOMEM; break; } used_obj = handle_to_obj(handle); free_obj = obj_malloc(d_page, class, handle); zs_object_copy(used_obj, free_obj, class); index++; record_obj(handle, free_obj); unpin_tag(handle); obj_free(pool, class, used_obj); nr_migrated++; } /* Remember last position in this iteration */ cc->s_page = s_page; cc->index = index; cc->nr_migrated = nr_migrated; return ret; } static struct page *alloc_target_page(struct size_class *class) { int i; struct page *page; for (i = 0; i < _ZS_NR_FULLNESS_GROUPS; i++) { page = class->fullness_list[i]; if (page) { remove_zspage(page, class, i); break; } } return page; } static void putback_zspage(struct zs_pool *pool, struct size_class *class, struct page *first_page) { int class_idx; enum fullness_group fullness; BUG_ON(!is_first_page(first_page)); get_zspage_mapping(first_page, &class_idx, &fullness); insert_zspage(first_page, class, fullness); fullness = fix_fullness_group(class, first_page); if (fullness == ZS_EMPTY) { zs_stat_dec(class, OBJ_ALLOCATED, get_maxobj_per_zspage( class->size, class->pages_per_zspage)); atomic_long_sub(class->pages_per_zspage, &pool->pages_allocated); free_zspage(first_page); } } static struct page *isolate_source_page(struct size_class *class) { struct page *page; page = class->fullness_list[ZS_ALMOST_EMPTY]; if (page) remove_zspage(page, class, ZS_ALMOST_EMPTY); return page; } static unsigned long __zs_compact(struct zs_pool *pool, struct size_class *class) { int nr_to_migrate; struct zs_compact_control cc; struct page *src_page; struct page *dst_page = NULL; unsigned long nr_total_migrated = 0; cond_resched(); spin_lock(&class->lock); while ((src_page = isolate_source_page(class))) { BUG_ON(!is_first_page(src_page)); /* The goal is to migrate all live objects in source page */ nr_to_migrate = src_page->inuse; cc.index = 0; cc.s_page = src_page; while ((dst_page = alloc_target_page(class))) { cc.d_page = dst_page; /* * If there is no more space in dst_page, try to * allocate another zspage. */ if (!migrate_zspage(pool, class, &cc)) break; putback_zspage(pool, class, dst_page); nr_total_migrated += cc.nr_migrated; nr_to_migrate -= cc.nr_migrated; } /* Stop if we couldn't find slot */ if (dst_page == NULL) break; putback_zspage(pool, class, dst_page); putback_zspage(pool, class, src_page); spin_unlock(&class->lock); nr_total_migrated += cc.nr_migrated; cond_resched(); spin_lock(&class->lock); } if (src_page) putback_zspage(pool, class, src_page); spin_unlock(&class->lock); return nr_total_migrated; } unsigned long zs_compact(struct zs_pool *pool) { int i; unsigned long nr_migrated = 0; struct size_class *class; for (i = zs_size_classes - 1; i >= 0; i--) { class = pool->size_class[i]; if (!class) continue; if (class->index != i) continue; nr_migrated += __zs_compact(pool, class); } synchronize_rcu(); return nr_migrated; } EXPORT_SYMBOL_GPL(zs_compact); /** * zs_create_pool - Creates an allocation pool to work from. * @flags: allocation flags used to allocate pool metadata * * This function must be called before anything when using * the zsmalloc allocator. * * On success, a pointer to the newly created pool is returned, * otherwise NULL. */ struct zs_pool *zs_create_pool(char *name, gfp_t flags) { int i; struct zs_pool *pool; struct size_class *prev_class = NULL; pool = kzalloc(sizeof(*pool), GFP_KERNEL); if (!pool) return NULL; pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *), GFP_KERNEL); if (!pool->size_class) { kfree(pool); return NULL; } pool->name = kstrdup(name, GFP_KERNEL); if (!pool->name) goto err; if (create_handle_cache(pool)) goto err; /* * Iterate reversly, because, size of size_class that we want to use * for merging should be larger or equal to current size. */ for (i = zs_size_classes - 1; i >= 0; i--) { int size; int pages_per_zspage; struct size_class *class; size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA; if (size > ZS_MAX_ALLOC_SIZE) size = ZS_MAX_ALLOC_SIZE; pages_per_zspage = get_pages_per_zspage(size); /* * size_class is used for normal zsmalloc operation such * as alloc/free for that size. Although it is natural that we * have one size_class for each size, there is a chance that we * can get more memory utilization if we use one size_class for * many different sizes whose size_class have same * characteristics. So, we makes size_class point to * previous size_class if possible. */ if (prev_class) { if (can_merge(prev_class, size, pages_per_zspage)) { pool->size_class[i] = prev_class; continue; } } class = kzalloc(sizeof(struct size_class), GFP_KERNEL); if (!class) goto err; class->size = size; class->index = i; class->pages_per_zspage = pages_per_zspage; if (pages_per_zspage == 1 && get_maxobj_per_zspage(size, pages_per_zspage) == 1) class->huge = true; spin_lock_init(&class->lock); pool->size_class[i] = class; prev_class = class; } pool->flags = flags; if (zs_pool_stat_create(name, pool)) goto err; return pool; err: zs_destroy_pool(pool); return NULL; } EXPORT_SYMBOL_GPL(zs_create_pool); void zs_destroy_pool(struct zs_pool *pool) { int i; zs_pool_stat_destroy(pool); for (i = 0; i < zs_size_classes; i++) { int fg; struct size_class *class = pool->size_class[i]; if (!class) continue; if (class->index != i) continue; for (fg = 0; fg < _ZS_NR_FULLNESS_GROUPS; fg++) { if (class->fullness_list[fg]) { pr_info("Freeing non-empty class with size %db, fullness group %d\n", class->size, fg); } } kfree(class); } destroy_handle_cache(pool); kfree(pool->size_class); kfree(pool->name); kfree(pool); } EXPORT_SYMBOL_GPL(zs_destroy_pool); static int __init zs_init(void) { int ret = zs_register_cpu_notifier(); if (ret) goto notifier_fail; init_zs_size_classes(); #ifdef CONFIG_ZPOOL zpool_register_driver(&zs_zpool_driver); #endif ret = zs_stat_init(); if (ret) { pr_err("zs stat initialization failed\n"); goto stat_fail; } return 0; stat_fail: #ifdef CONFIG_ZPOOL zpool_unregister_driver(&zs_zpool_driver); #endif notifier_fail: zs_unregister_cpu_notifier(); return ret; } static void __exit zs_exit(void) { #ifdef CONFIG_ZPOOL zpool_unregister_driver(&zs_zpool_driver); #endif zs_unregister_cpu_notifier(); zs_stat_exit(); } module_init(zs_init); module_exit(zs_exit); MODULE_LICENSE("Dual BSD/GPL"); MODULE_AUTHOR("Nitin Gupta ");