/* * 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 */ /* * Following is how we use various fields and flags of underlying * struct page(s) to form a zspage. * * Usage of struct page fields: * page->private: points to zspage * page->freelist(index): links together all component pages of a zspage * For the huge page, this is always 0, so we use this field * to store handle. * page->units: first object offset in a subpage of zspage * * Usage of struct page flags: * PG_private: identifies the first component page * PG_owner_priv_1: identifies the huge component page * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define ZSPAGE_MAGIC 0x58 /* * 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 * a single (unsigned long) handle value. * * Note that object index starts from 0. * * This is made more complicated by various memory models and PAE. */ #ifndef MAX_POSSIBLE_PHYSMEM_BITS #ifdef MAX_PHYSMEM_BITS #define MAX_POSSIBLE_PHYSMEM_BITS MAX_PHYSMEM_BITS #else /* * If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just * be PAGE_SHIFT */ #define MAX_POSSIBLE_PHYSMEM_BITS BITS_PER_LONG #endif #endif #define _PFN_BITS (MAX_POSSIBLE_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 FULLNESS_BITS 2 #define CLASS_BITS 8 #define ISOLATED_BITS 3 #define MAGIC_VAL_BITS 8 #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 >> CLASS_BITS) #define ZS_SIZE_CLASSES (DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \ ZS_SIZE_CLASS_DELTA) + 1) enum fullness_group { ZS_EMPTY, ZS_ALMOST_EMPTY, ZS_ALMOST_FULL, ZS_FULL, NR_ZS_FULLNESS, }; enum zs_stat_type { CLASS_EMPTY, CLASS_ALMOST_EMPTY, CLASS_ALMOST_FULL, CLASS_FULL, OBJ_ALLOCATED, OBJ_USED, NR_ZS_STAT_TYPE, }; struct zs_size_stat { unsigned long objs[NR_ZS_STAT_TYPE]; }; #ifdef CONFIG_ZSMALLOC_STAT static struct dentry *zs_stat_root; #endif #ifdef CONFIG_COMPACTION static struct vfsmount *zsmalloc_mnt; #endif /* * 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; static size_t huge_class_size; struct size_class { spinlock_t lock; struct list_head fullness_list[NR_ZS_FULLNESS]; /* * Size of objects stored in this class. Must be multiple * of ZS_ALIGN. */ int size; int objs_per_zspage; /* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */ int pages_per_zspage; unsigned int index; struct zs_size_stat stats; }; /* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */ static void SetPageHugeObject(struct page *page) { SetPageOwnerPriv1(page); } static void ClearPageHugeObject(struct page *page) { ClearPageOwnerPriv1(page); } static int PageHugeObject(struct page *page) { return PageOwnerPriv1(page); } /* * Placed within free objects to form a singly linked list. * For every zspage, zspage->freeobj gives head of this list. * * This must be power of 2 and less than or equal to ZS_ALIGN */ struct link_free { union { /* * Free object index; * It's valid for non-allocated object */ unsigned long next; /* * Handle of allocated object. */ unsigned long handle; }; }; struct zs_pool { const char *name; struct size_class *size_class[ZS_SIZE_CLASSES]; struct kmem_cache *handle_cachep; struct kmem_cache *zspage_cachep; atomic_long_t pages_allocated; struct zs_pool_stats stats; /* Compact classes */ struct shrinker shrinker; #ifdef CONFIG_ZSMALLOC_STAT struct dentry *stat_dentry; #endif #ifdef CONFIG_COMPACTION struct inode *inode; struct work_struct free_work; /* A wait queue for when migration races with async_free_zspage() */ struct wait_queue_head migration_wait; atomic_long_t isolated_pages; bool destroying; #endif }; struct zspage { struct { unsigned int fullness:FULLNESS_BITS; unsigned int class:CLASS_BITS + 1; unsigned int isolated:ISOLATED_BITS; unsigned int magic:MAGIC_VAL_BITS; }; unsigned int inuse; unsigned int freeobj; struct page *first_page; struct list_head list; /* fullness list */ #ifdef CONFIG_COMPACTION rwlock_t lock; #endif }; struct mapping_area { char *vm_buf; /* copy buffer for objects that span pages */ char *vm_addr; /* address of kmap_atomic()'ed pages */ enum zs_mapmode vm_mm; /* mapping mode */ }; #ifdef CONFIG_COMPACTION static int zs_register_migration(struct zs_pool *pool); static void zs_unregister_migration(struct zs_pool *pool); static void migrate_lock_init(struct zspage *zspage); static void migrate_read_lock(struct zspage *zspage); static void migrate_read_unlock(struct zspage *zspage); static void kick_deferred_free(struct zs_pool *pool); static void init_deferred_free(struct zs_pool *pool); static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage); #else static int zsmalloc_mount(void) { return 0; } static void zsmalloc_unmount(void) {} static int zs_register_migration(struct zs_pool *pool) { return 0; } static void zs_unregister_migration(struct zs_pool *pool) {} static void migrate_lock_init(struct zspage *zspage) {} static void migrate_read_lock(struct zspage *zspage) {} static void migrate_read_unlock(struct zspage *zspage) {} static void kick_deferred_free(struct zs_pool *pool) {} static void init_deferred_free(struct zs_pool *pool) {} static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) {} #endif static int create_cache(struct zs_pool *pool) { pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE, 0, 0, NULL); if (!pool->handle_cachep) return 1; pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage), 0, 0, NULL); if (!pool->zspage_cachep) { kmem_cache_destroy(pool->handle_cachep); pool->handle_cachep = NULL; return 1; } return 0; } static void destroy_cache(struct zs_pool *pool) { kmem_cache_destroy(pool->handle_cachep); kmem_cache_destroy(pool->zspage_cachep); } static unsigned long cache_alloc_handle(struct zs_pool *pool, gfp_t gfp) { return (unsigned long)kmem_cache_alloc(pool->handle_cachep, gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE|__GFP_CMA)); } static void cache_free_handle(struct zs_pool *pool, unsigned long handle) { kmem_cache_free(pool->handle_cachep, (void *)handle); } static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags) { return kmem_cache_alloc(pool->zspage_cachep, flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE|__GFP_CMA)); } static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage) { kmem_cache_free(pool->zspage_cachep, zspage); } static void record_obj(unsigned long handle, unsigned long obj) { /* * lsb of @obj represents handle lock while other bits * represent object value the handle is pointing so * updating shouldn't do store tearing. */ WRITE_ONCE(*(unsigned long *)handle, obj); } /* zpool driver */ #ifdef CONFIG_ZPOOL static void *zs_zpool_create(const char *name, gfp_t gfp, const struct zpool_ops *zpool_ops, struct zpool *zpool) { /* * Ignore global gfp flags: zs_malloc() may be invoked from * different contexts and its caller must provide a valid * gfp mask. */ return zs_create_pool(name); } 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, gfp); return *handle ? 0 : -1; } static void zs_zpool_free(void *pool, unsigned long handle) { zs_free(pool, handle); } 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: 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_support_movable = true, .malloc = zs_zpool_malloc, .free = zs_zpool_free, .map = zs_zpool_map, .unmap = zs_zpool_unmap, .total_size = zs_zpool_total_size, }; MODULE_ALIAS("zpool-zsmalloc"); #endif /* CONFIG_ZPOOL */ /* per-cpu VM mapping areas for zspage accesses that cross page boundaries */ static DEFINE_PER_CPU(struct mapping_area, zs_map_area); static bool is_zspage_isolated(struct zspage *zspage) { return zspage->isolated; } static __maybe_unused int is_first_page(struct page *page) { return PagePrivate(page); } /* Protected by class->lock */ static inline int get_zspage_inuse(struct zspage *zspage) { return zspage->inuse; } static inline void mod_zspage_inuse(struct zspage *zspage, int val) { zspage->inuse += val; } static inline struct page *get_first_page(struct zspage *zspage) { struct page *first_page = zspage->first_page; VM_BUG_ON_PAGE(!is_first_page(first_page), first_page); return first_page; } static inline int get_first_obj_offset(struct page *page) { return page->units; } static inline void set_first_obj_offset(struct page *page, int offset) { page->units = offset; } static inline unsigned int get_freeobj(struct zspage *zspage) { return zspage->freeobj; } static inline void set_freeobj(struct zspage *zspage, unsigned int obj) { zspage->freeobj = obj; } static void get_zspage_mapping(struct zspage *zspage, unsigned int *class_idx, enum fullness_group *fullness) { BUG_ON(zspage->magic != ZSPAGE_MAGIC); *fullness = zspage->fullness; *class_idx = zspage->class; } static void set_zspage_mapping(struct zspage *zspage, unsigned int class_idx, enum fullness_group fullness) { zspage->class = class_idx; zspage->fullness = fullness; } /* * 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_t(int, ZS_SIZE_CLASSES - 1, idx); } /* type can be of enum type zs_stat_type or fullness_group */ static inline void zs_stat_inc(struct size_class *class, int type, unsigned long cnt) { class->stats.objs[type] += cnt; } /* type can be of enum type zs_stat_type or fullness_group */ static inline void zs_stat_dec(struct size_class *class, int type, unsigned long cnt) { class->stats.objs[type] -= cnt; } /* type can be of enum type zs_stat_type or fullness_group */ static inline unsigned long zs_stat_get(struct size_class *class, int type) { return class->stats.objs[type]; } #ifdef CONFIG_ZSMALLOC_STAT static void __init zs_stat_init(void) { if (!debugfs_initialized()) { pr_warn("debugfs not available, stat dir not created\n"); return; } zs_stat_root = debugfs_create_dir("zsmalloc", NULL); } static void __exit zs_stat_exit(void) { debugfs_remove_recursive(zs_stat_root); } static unsigned long zs_can_compact(struct size_class *class); 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, freeable; unsigned long total_class_almost_full = 0, total_class_almost_empty = 0; unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0; unsigned long total_freeable = 0; seq_printf(s, " %5s %5s %11s %12s %13s %10s %10s %16s %8s\n", "class", "size", "almost_full", "almost_empty", "obj_allocated", "obj_used", "pages_used", "pages_per_zspage", "freeable"); 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); freeable = zs_can_compact(class); spin_unlock(&class->lock); objs_per_zspage = class->objs_per_zspage; pages_used = obj_allocated / objs_per_zspage * class->pages_per_zspage; seq_printf(s, " %5u %5u %11lu %12lu %13lu" " %10lu %10lu %16d %8lu\n", i, class->size, class_almost_full, class_almost_empty, obj_allocated, obj_used, pages_used, class->pages_per_zspage, freeable); 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; total_freeable += freeable; } seq_puts(s, "\n"); seq_printf(s, " %5s %5s %11lu %12lu %13lu %10lu %10lu %16s %8lu\n", "Total", "", total_class_almost_full, total_class_almost_empty, total_objs, total_used_objs, total_pages, "", total_freeable); return 0; } DEFINE_SHOW_ATTRIBUTE(zs_stats_size); static void zs_pool_stat_create(struct zs_pool *pool, const char *name) { if (!zs_stat_root) { pr_warn("no root stat dir, not creating <%s> stat dir\n", name); return; } pool->stat_dentry = debugfs_create_dir(name, zs_stat_root); debugfs_create_file("classes", S_IFREG | 0444, pool->stat_dentry, pool, &zs_stats_size_fops); } static void zs_pool_stat_destroy(struct zs_pool *pool) { debugfs_remove_recursive(pool->stat_dentry); } #else /* CONFIG_ZSMALLOC_STAT */ static void __init zs_stat_init(void) { } static void __exit zs_stat_exit(void) { } static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name) { } 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 size_class *class, struct zspage *zspage) { int inuse, objs_per_zspage; enum fullness_group fg; inuse = get_zspage_inuse(zspage); objs_per_zspage = class->objs_per_zspage; if (inuse == 0) fg = ZS_EMPTY; else if (inuse == objs_per_zspage) fg = ZS_FULL; else if (inuse <= 3 * objs_per_zspage / 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 size_class *class, struct zspage *zspage, enum fullness_group fullness) { struct zspage *head; zs_stat_inc(class, fullness, 1); head = list_first_entry_or_null(&class->fullness_list[fullness], struct zspage, list); /* * We want to see more ZS_FULL pages and less almost empty/full. * Put pages with higher ->inuse first. */ if (head) { if (get_zspage_inuse(zspage) < get_zspage_inuse(head)) { list_add(&zspage->list, &head->list); return; } } list_add(&zspage->list, &class->fullness_list[fullness]); } /* * This function removes the given zspage from the freelist identified * by . */ static void remove_zspage(struct size_class *class, struct zspage *zspage, enum fullness_group fullness) { VM_BUG_ON(list_empty(&class->fullness_list[fullness])); VM_BUG_ON(is_zspage_isolated(zspage)); list_del_init(&zspage->list); zs_stat_dec(class, fullness, 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 zspage *zspage) { int class_idx; enum fullness_group currfg, newfg; get_zspage_mapping(zspage, &class_idx, &currfg); newfg = get_fullness_group(class, zspage); if (newfg == currfg) goto out; if (!is_zspage_isolated(zspage)) { remove_zspage(class, zspage, currfg); insert_zspage(class, zspage, newfg); } set_zspage_mapping(zspage, 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 % class_size * usage = Zp - wastage * 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; } static struct zspage *get_zspage(struct page *page) { struct zspage *zspage = (struct zspage *)page->private; BUG_ON(zspage->magic != ZSPAGE_MAGIC); return zspage; } static struct page *get_next_page(struct page *page) { if (unlikely(PageHugeObject(page))) return NULL; return page->freelist; } /** * obj_to_location - get (, ) from encoded object value * @obj: the encoded object value * @page: page object resides in zspage * @obj_idx: object index */ static void obj_to_location(unsigned long obj, struct page **page, unsigned int *obj_idx) { obj >>= OBJ_TAG_BITS; *page = pfn_to_page(obj >> OBJ_INDEX_BITS); *obj_idx = (obj & OBJ_INDEX_MASK); } /** * location_to_obj - get obj value encoded from (, ) * @page: page object resides in zspage * @obj_idx: object index */ static unsigned long location_to_obj(struct page *page, unsigned int obj_idx) { unsigned long obj; obj = page_to_pfn(page) << OBJ_INDEX_BITS; obj |= obj_idx & OBJ_INDEX_MASK; obj <<= OBJ_TAG_BITS; return obj; } static unsigned long handle_to_obj(unsigned long handle) { return *(unsigned long *)handle; } static unsigned long obj_to_head(struct page *page, void *obj) { if (unlikely(PageHugeObject(page))) { VM_BUG_ON_PAGE(!is_first_page(page), page); return page->index; } else return *(unsigned long *)obj; } static inline int testpin_tag(unsigned long handle) { return bit_spin_is_locked(HANDLE_PIN_BIT, (unsigned long *)handle); } static inline int trypin_tag(unsigned long handle) { return bit_spin_trylock(HANDLE_PIN_BIT, (unsigned long *)handle); } static void pin_tag(unsigned long handle) __acquires(bitlock) { bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle); } static void unpin_tag(unsigned long handle) __releases(bitlock) { bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle); } static void reset_page(struct page *page) { __ClearPageMovable(page); ClearPagePrivate(page); set_page_private(page, 0); page_mapcount_reset(page); ClearPageHugeObject(page); page->freelist = NULL; } static int trylock_zspage(struct zspage *zspage) { struct page *cursor, *fail; for (cursor = get_first_page(zspage); cursor != NULL; cursor = get_next_page(cursor)) { if (!trylock_page(cursor)) { fail = cursor; goto unlock; } } return 1; unlock: for (cursor = get_first_page(zspage); cursor != fail; cursor = get_next_page(cursor)) unlock_page(cursor); return 0; } static void __free_zspage(struct zs_pool *pool, struct size_class *class, struct zspage *zspage) { struct page *page, *next; enum fullness_group fg; unsigned int class_idx; get_zspage_mapping(zspage, &class_idx, &fg); assert_spin_locked(&class->lock); VM_BUG_ON(get_zspage_inuse(zspage)); VM_BUG_ON(fg != ZS_EMPTY); next = page = get_first_page(zspage); do { VM_BUG_ON_PAGE(!PageLocked(page), page); next = get_next_page(page); reset_page(page); unlock_page(page); dec_zone_page_state(page, NR_ZSPAGES); put_page(page); page = next; } while (page != NULL); cache_free_zspage(pool, zspage); zs_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage); atomic_long_sub(class->pages_per_zspage, &pool->pages_allocated); } static void free_zspage(struct zs_pool *pool, struct size_class *class, struct zspage *zspage) { VM_BUG_ON(get_zspage_inuse(zspage)); VM_BUG_ON(list_empty(&zspage->list)); if (!trylock_zspage(zspage)) { kick_deferred_free(pool); return; } remove_zspage(class, zspage, ZS_EMPTY); __free_zspage(pool, class, zspage); } /* Initialize a newly allocated zspage */ static void init_zspage(struct size_class *class, struct zspage *zspage) { unsigned int freeobj = 1; unsigned long off = 0; struct page *page = get_first_page(zspage); while (page) { struct page *next_page; struct link_free *link; void *vaddr; set_first_obj_offset(page, off); vaddr = kmap_atomic(page); link = (struct link_free *)vaddr + off / sizeof(*link); while ((off += class->size) < PAGE_SIZE) { link->next = freeobj++ << OBJ_TAG_BITS; 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); if (next_page) { link->next = freeobj++ << OBJ_TAG_BITS; } else { /* * Reset OBJ_TAG_BITS bit to last link to tell * whether it's allocated object or not. */ link->next = -1UL << OBJ_TAG_BITS; } kunmap_atomic(vaddr); page = next_page; off %= PAGE_SIZE; } set_freeobj(zspage, 0); } static void create_page_chain(struct size_class *class, struct zspage *zspage, struct page *pages[]) { int i; struct page *page; struct page *prev_page = NULL; int nr_pages = class->pages_per_zspage; /* * Allocate individual pages and link them together as: * 1. all pages are linked together using page->freelist * 2. each sub-page point to zspage using page->private * * we set PG_private to identify the first page (i.e. no other sub-page * has this flag set). */ for (i = 0; i < nr_pages; i++) { page = pages[i]; set_page_private(page, (unsigned long)zspage); page->freelist = NULL; if (i == 0) { zspage->first_page = page; SetPagePrivate(page); if (unlikely(class->objs_per_zspage == 1 && class->pages_per_zspage == 1)) SetPageHugeObject(page); } else { prev_page->freelist = page; } prev_page = page; } } /* * Allocate a zspage for the given size class */ static struct zspage *alloc_zspage(struct zs_pool *pool, struct size_class *class, gfp_t gfp) { int i; struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE]; struct zspage *zspage = cache_alloc_zspage(pool, gfp); if (!zspage) return NULL; memset(zspage, 0, sizeof(struct zspage)); zspage->magic = ZSPAGE_MAGIC; migrate_lock_init(zspage); for (i = 0; i < class->pages_per_zspage; i++) { struct page *page; page = alloc_page(gfp); if (!page) { while (--i >= 0) { dec_zone_page_state(pages[i], NR_ZSPAGES); __free_page(pages[i]); } cache_free_zspage(pool, zspage); return NULL; } inc_zone_page_state(page, NR_ZSPAGES); pages[i] = page; } create_page_chain(class, zspage, pages); init_zspage(class, zspage); return zspage; } static struct zspage *find_get_zspage(struct size_class *class) { int i; struct zspage *zspage; for (i = ZS_ALMOST_FULL; i >= ZS_EMPTY; i--) { zspage = list_first_entry_or_null(&class->fullness_list[i], struct zspage, list); if (zspage) break; } return zspage; } 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; 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(); } static int zs_cpu_prepare(unsigned int cpu) { struct mapping_area *area; area = &per_cpu(zs_map_area, cpu); return __zs_cpu_up(area); } static int zs_cpu_dead(unsigned int cpu) { struct mapping_area *area; area = &per_cpu(zs_map_area, cpu); __zs_cpu_down(area); return 0; } static bool can_merge(struct size_class *prev, int pages_per_zspage, int objs_per_zspage) { if (prev->pages_per_zspage == pages_per_zspage && prev->objs_per_zspage == objs_per_zspage) return true; return false; } static bool zspage_full(struct size_class *class, struct zspage *zspage) { return get_zspage_inuse(zspage) == class->objs_per_zspage; } 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 * @mm: maping mode to use * * 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 zspage *zspage; struct page *page; unsigned long obj, off; unsigned int obj_idx; unsigned int class_idx; enum fullness_group fg; struct size_class *class; struct mapping_area *area; struct page *pages[2]; void *ret; /* * 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); zspage = get_zspage(page); /* migration cannot move any subpage in this zspage */ migrate_read_lock(zspage); get_zspage_mapping(zspage, &class_idx, &fg); class = pool->size_class[class_idx]; off = (class->size * obj_idx) & ~PAGE_MASK; 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 (likely(!PageHugeObject(page))) ret += ZS_HANDLE_SIZE; return ret; } EXPORT_SYMBOL_GPL(zs_map_object); void zs_unmap_object(struct zs_pool *pool, unsigned long handle) { struct zspage *zspage; struct page *page; unsigned long obj, off; unsigned int obj_idx; unsigned int class_idx; enum fullness_group fg; struct size_class *class; struct mapping_area *area; obj = handle_to_obj(handle); obj_to_location(obj, &page, &obj_idx); zspage = get_zspage(page); get_zspage_mapping(zspage, &class_idx, &fg); class = pool->size_class[class_idx]; off = (class->size * obj_idx) & ~PAGE_MASK; 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); migrate_read_unlock(zspage); unpin_tag(handle); } EXPORT_SYMBOL_GPL(zs_unmap_object); /** * zs_huge_class_size() - Returns the size (in bytes) of the first huge * zsmalloc &size_class. * @pool: zsmalloc pool to use * * The function returns the size of the first huge class - any object of equal * or bigger size will be stored in zspage consisting of a single physical * page. * * Context: Any context. * * Return: the size (in bytes) of the first huge zsmalloc &size_class. */ size_t zs_huge_class_size(struct zs_pool *pool) { return huge_class_size; } EXPORT_SYMBOL_GPL(zs_huge_class_size); static unsigned long obj_malloc(struct size_class *class, struct zspage *zspage, unsigned long handle) { int i, nr_page, offset; unsigned long obj; struct link_free *link; struct page *m_page; unsigned long m_offset; void *vaddr; handle |= OBJ_ALLOCATED_TAG; obj = get_freeobj(zspage); offset = obj * class->size; nr_page = offset >> PAGE_SHIFT; m_offset = offset & ~PAGE_MASK; m_page = get_first_page(zspage); for (i = 0; i < nr_page; i++) m_page = get_next_page(m_page); vaddr = kmap_atomic(m_page); link = (struct link_free *)vaddr + m_offset / sizeof(*link); set_freeobj(zspage, link->next >> OBJ_TAG_BITS); if (likely(!PageHugeObject(m_page))) /* record handle in the header of allocated chunk */ link->handle = handle; else /* record handle to page->index */ zspage->first_page->index = handle; kunmap_atomic(vaddr); mod_zspage_inuse(zspage, 1); zs_stat_inc(class, OBJ_USED, 1); obj = location_to_obj(m_page, obj); return obj; } /** * zs_malloc - Allocate block of given size from pool. * @pool: pool to allocate from * @size: size of block to allocate * @gfp: gfp flags when allocating object * * 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, gfp_t gfp) { unsigned long handle, obj; struct size_class *class; enum fullness_group newfg; struct zspage *zspage; if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE)) return 0; handle = cache_alloc_handle(pool, gfp); 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)]; spin_lock(&class->lock); zspage = find_get_zspage(class); if (likely(zspage)) { obj = obj_malloc(class, zspage, handle); /* Now move the zspage to another fullness group, if required */ fix_fullness_group(class, zspage); record_obj(handle, obj); spin_unlock(&class->lock); return handle; } spin_unlock(&class->lock); zspage = alloc_zspage(pool, class, gfp); if (!zspage) { cache_free_handle(pool, handle); return 0; } spin_lock(&class->lock); obj = obj_malloc(class, zspage, handle); newfg = get_fullness_group(class, zspage); insert_zspage(class, zspage, newfg); set_zspage_mapping(zspage, class->index, newfg); record_obj(handle, obj); atomic_long_add(class->pages_per_zspage, &pool->pages_allocated); zs_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage); /* We completely set up zspage so mark them as movable */ SetZsPageMovable(pool, zspage); spin_unlock(&class->lock); return handle; } EXPORT_SYMBOL_GPL(zs_malloc); static void obj_free(struct size_class *class, unsigned long obj) { struct link_free *link; struct zspage *zspage; struct page *f_page; unsigned long f_offset; unsigned int f_objidx; void *vaddr; obj &= ~OBJ_ALLOCATED_TAG; obj_to_location(obj, &f_page, &f_objidx); f_offset = (class->size * f_objidx) & ~PAGE_MASK; zspage = get_zspage(f_page); vaddr = kmap_atomic(f_page); /* Insert this object in containing zspage's freelist */ link = (struct link_free *)(vaddr + f_offset); link->next = get_freeobj(zspage) << OBJ_TAG_BITS; kunmap_atomic(vaddr); set_freeobj(zspage, f_objidx); mod_zspage_inuse(zspage, -1); zs_stat_dec(class, OBJ_USED, 1); } void zs_free(struct zs_pool *pool, unsigned long handle) { struct zspage *zspage; struct page *f_page; unsigned long obj; unsigned int f_objidx; int class_idx; struct size_class *class; enum fullness_group fullness; bool isolated; if (unlikely(!handle)) return; pin_tag(handle); obj = handle_to_obj(handle); obj_to_location(obj, &f_page, &f_objidx); zspage = get_zspage(f_page); migrate_read_lock(zspage); get_zspage_mapping(zspage, &class_idx, &fullness); class = pool->size_class[class_idx]; spin_lock(&class->lock); obj_free(class, obj); fullness = fix_fullness_group(class, zspage); if (fullness != ZS_EMPTY) { migrate_read_unlock(zspage); goto out; } isolated = is_zspage_isolated(zspage); migrate_read_unlock(zspage); /* If zspage is isolated, zs_page_putback will free the zspage */ if (likely(!isolated)) free_zspage(pool, class, zspage); out: spin_unlock(&class->lock); unpin_tag(handle); cache_free_handle(pool, handle); } EXPORT_SYMBOL_GPL(zs_free); static void zs_object_copy(struct size_class *class, unsigned long dst, unsigned long src) { struct page *s_page, *d_page; unsigned int 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 = (class->size * s_objidx) & ~PAGE_MASK; d_off = (class->size * d_objidx) & ~PAGE_MASK; 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; s_off += size; s_size -= size; d_off += size; d_size -= size; if (s_off >= PAGE_SIZE) { kunmap_atomic(d_addr); kunmap_atomic(s_addr); s_page = get_next_page(s_page); s_addr = kmap_atomic(s_page); d_addr = kmap_atomic(d_page); s_size = class->size - written; s_off = 0; } if (d_off >= PAGE_SIZE) { kunmap_atomic(d_addr); d_page = get_next_page(d_page); d_addr = kmap_atomic(d_page); d_size = class->size - written; d_off = 0; } } 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 size_class *class, struct page *page, int *obj_idx) { unsigned long head; int offset = 0; int index = *obj_idx; unsigned long handle = 0; void *addr = kmap_atomic(page); offset = get_first_obj_offset(page); offset += class->size * index; while (offset < PAGE_SIZE) { head = obj_to_head(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); *obj_idx = index; return handle; } struct zs_compact_control { /* Source spage 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 obj_idx; }; 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; int obj_idx = cc->obj_idx; int ret = 0; while (1) { handle = find_alloced_obj(class, s_page, &obj_idx); if (!handle) { s_page = get_next_page(s_page); if (!s_page) break; obj_idx = 0; continue; } /* Stop if there is no more space */ if (zspage_full(class, get_zspage(d_page))) { unpin_tag(handle); ret = -ENOMEM; break; } used_obj = handle_to_obj(handle); free_obj = obj_malloc(class, get_zspage(d_page), handle); zs_object_copy(class, free_obj, used_obj); obj_idx++; /* * record_obj updates handle's value to free_obj and it will * invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which * breaks synchronization using pin_tag(e,g, zs_free) so * let's keep the lock bit. */ free_obj |= BIT(HANDLE_PIN_BIT); record_obj(handle, free_obj); unpin_tag(handle); obj_free(class, used_obj); } /* Remember last position in this iteration */ cc->s_page = s_page; cc->obj_idx = obj_idx; return ret; } static struct zspage *isolate_zspage(struct size_class *class, bool source) { int i; struct zspage *zspage; enum fullness_group fg[2] = {ZS_ALMOST_EMPTY, ZS_ALMOST_FULL}; if (!source) { fg[0] = ZS_ALMOST_FULL; fg[1] = ZS_ALMOST_EMPTY; } for (i = 0; i < 2; i++) { zspage = list_first_entry_or_null(&class->fullness_list[fg[i]], struct zspage, list); if (zspage) { VM_BUG_ON(is_zspage_isolated(zspage)); remove_zspage(class, zspage, fg[i]); return zspage; } } return zspage; } /* * putback_zspage - add @zspage into right class's fullness list * @class: destination class * @zspage: target page * * Return @zspage's fullness_group */ static enum fullness_group putback_zspage(struct size_class *class, struct zspage *zspage) { enum fullness_group fullness; VM_BUG_ON(is_zspage_isolated(zspage)); fullness = get_fullness_group(class, zspage); insert_zspage(class, zspage, fullness); set_zspage_mapping(zspage, class->index, fullness); return fullness; } #ifdef CONFIG_COMPACTION /* * To prevent zspage destroy during migration, zspage freeing should * hold locks of all pages in the zspage. */ static void lock_zspage(struct zspage *zspage) { struct page *page = get_first_page(zspage); do { lock_page(page); } while ((page = get_next_page(page)) != NULL); } static int zs_init_fs_context(struct fs_context *fc) { return init_pseudo(fc, ZSMALLOC_MAGIC) ? 0 : -ENOMEM; } static struct file_system_type zsmalloc_fs = { .name = "zsmalloc", .init_fs_context = zs_init_fs_context, .kill_sb = kill_anon_super, }; static int zsmalloc_mount(void) { int ret = 0; zsmalloc_mnt = kern_mount(&zsmalloc_fs); if (IS_ERR(zsmalloc_mnt)) ret = PTR_ERR(zsmalloc_mnt); return ret; } static void zsmalloc_unmount(void) { kern_unmount(zsmalloc_mnt); } static void migrate_lock_init(struct zspage *zspage) { rwlock_init(&zspage->lock); } static void migrate_read_lock(struct zspage *zspage) __acquires(&zspage->lock) { read_lock(&zspage->lock); } static void migrate_read_unlock(struct zspage *zspage) __releases(&zspage->lock) { read_unlock(&zspage->lock); } static void migrate_write_lock(struct zspage *zspage) { write_lock(&zspage->lock); } static void migrate_write_unlock(struct zspage *zspage) { write_unlock(&zspage->lock); } /* Number of isolated subpage for *page migration* in this zspage */ static void inc_zspage_isolation(struct zspage *zspage) { zspage->isolated++; } static void dec_zspage_isolation(struct zspage *zspage) { zspage->isolated--; } static void putback_zspage_deferred(struct zs_pool *pool, struct size_class *class, struct zspage *zspage) { enum fullness_group fg; fg = putback_zspage(class, zspage); if (fg == ZS_EMPTY) schedule_work(&pool->free_work); } static inline void zs_pool_dec_isolated(struct zs_pool *pool) { VM_BUG_ON(atomic_long_read(&pool->isolated_pages) <= 0); atomic_long_dec(&pool->isolated_pages); /* * There's no possibility of racing, since wait_for_isolated_drain() * checks the isolated count under &class->lock after enqueuing * on migration_wait. */ if (atomic_long_read(&pool->isolated_pages) == 0 && pool->destroying) wake_up_all(&pool->migration_wait); } static void replace_sub_page(struct size_class *class, struct zspage *zspage, struct page *newpage, struct page *oldpage) { struct page *page; struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL, }; int idx = 0; page = get_first_page(zspage); do { if (page == oldpage) pages[idx] = newpage; else pages[idx] = page; idx++; } while ((page = get_next_page(page)) != NULL); create_page_chain(class, zspage, pages); set_first_obj_offset(newpage, get_first_obj_offset(oldpage)); if (unlikely(PageHugeObject(oldpage))) newpage->index = oldpage->index; __SetPageMovable(newpage, page_mapping(oldpage)); } static bool zs_page_isolate(struct page *page, isolate_mode_t mode) { struct zs_pool *pool; struct size_class *class; int class_idx; enum fullness_group fullness; struct zspage *zspage; struct address_space *mapping; /* * Page is locked so zspage couldn't be destroyed. For detail, look at * lock_zspage in free_zspage. */ VM_BUG_ON_PAGE(!PageMovable(page), page); VM_BUG_ON_PAGE(PageIsolated(page), page); zspage = get_zspage(page); /* * Without class lock, fullness could be stale while class_idx is okay * because class_idx is constant unless page is freed so we should get * fullness again under class lock. */ get_zspage_mapping(zspage, &class_idx, &fullness); mapping = page_mapping(page); pool = mapping->private_data; class = pool->size_class[class_idx]; spin_lock(&class->lock); if (get_zspage_inuse(zspage) == 0) { spin_unlock(&class->lock); return false; } /* zspage is isolated for object migration */ if (list_empty(&zspage->list) && !is_zspage_isolated(zspage)) { spin_unlock(&class->lock); return false; } /* * If this is first time isolation for the zspage, isolate zspage from * size_class to prevent further object allocation from the zspage. */ if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) { get_zspage_mapping(zspage, &class_idx, &fullness); atomic_long_inc(&pool->isolated_pages); remove_zspage(class, zspage, fullness); } inc_zspage_isolation(zspage); spin_unlock(&class->lock); return true; } static int zs_page_migrate(struct address_space *mapping, struct page *newpage, struct page *page, enum migrate_mode mode) { struct zs_pool *pool; struct size_class *class; int class_idx; enum fullness_group fullness; struct zspage *zspage; struct page *dummy; void *s_addr, *d_addr, *addr; int offset, pos; unsigned long handle, head; unsigned long old_obj, new_obj; unsigned int obj_idx; int ret = -EAGAIN; /* * We cannot support the _NO_COPY case here, because copy needs to * happen under the zs lock, which does not work with * MIGRATE_SYNC_NO_COPY workflow. */ if (mode == MIGRATE_SYNC_NO_COPY) return -EINVAL; VM_BUG_ON_PAGE(!PageMovable(page), page); VM_BUG_ON_PAGE(!PageIsolated(page), page); zspage = get_zspage(page); /* Concurrent compactor cannot migrate any subpage in zspage */ migrate_write_lock(zspage); get_zspage_mapping(zspage, &class_idx, &fullness); pool = mapping->private_data; class = pool->size_class[class_idx]; offset = get_first_obj_offset(page); spin_lock(&class->lock); if (!get_zspage_inuse(zspage)) { /* * Set "offset" to end of the page so that every loops * skips unnecessary object scanning. */ offset = PAGE_SIZE; } pos = offset; s_addr = kmap_atomic(page); while (pos < PAGE_SIZE) { head = obj_to_head(page, s_addr + pos); if (head & OBJ_ALLOCATED_TAG) { handle = head & ~OBJ_ALLOCATED_TAG; if (!trypin_tag(handle)) goto unpin_objects; } pos += class->size; } /* * Here, any user cannot access all objects in the zspage so let's move. */ d_addr = kmap_atomic(newpage); memcpy(d_addr, s_addr, PAGE_SIZE); kunmap_atomic(d_addr); for (addr = s_addr + offset; addr < s_addr + pos; addr += class->size) { head = obj_to_head(page, addr); if (head & OBJ_ALLOCATED_TAG) { handle = head & ~OBJ_ALLOCATED_TAG; if (!testpin_tag(handle)) BUG(); old_obj = handle_to_obj(handle); obj_to_location(old_obj, &dummy, &obj_idx); new_obj = (unsigned long)location_to_obj(newpage, obj_idx); new_obj |= BIT(HANDLE_PIN_BIT); record_obj(handle, new_obj); } } replace_sub_page(class, zspage, newpage, page); get_page(newpage); dec_zspage_isolation(zspage); /* * Page migration is done so let's putback isolated zspage to * the list if @page is final isolated subpage in the zspage. */ if (!is_zspage_isolated(zspage)) { /* * We cannot race with zs_destroy_pool() here because we wait * for isolation to hit zero before we start destroying. * Also, we ensure that everyone can see pool->destroying before * we start waiting. */ putback_zspage_deferred(pool, class, zspage); zs_pool_dec_isolated(pool); } if (page_zone(newpage) != page_zone(page)) { dec_zone_page_state(page, NR_ZSPAGES); inc_zone_page_state(newpage, NR_ZSPAGES); } reset_page(page); put_page(page); page = newpage; ret = MIGRATEPAGE_SUCCESS; unpin_objects: for (addr = s_addr + offset; addr < s_addr + pos; addr += class->size) { head = obj_to_head(page, addr); if (head & OBJ_ALLOCATED_TAG) { handle = head & ~OBJ_ALLOCATED_TAG; if (!testpin_tag(handle)) BUG(); unpin_tag(handle); } } kunmap_atomic(s_addr); spin_unlock(&class->lock); migrate_write_unlock(zspage); return ret; } static void zs_page_putback(struct page *page) { struct zs_pool *pool; struct size_class *class; int class_idx; enum fullness_group fg; struct address_space *mapping; struct zspage *zspage; VM_BUG_ON_PAGE(!PageMovable(page), page); VM_BUG_ON_PAGE(!PageIsolated(page), page); zspage = get_zspage(page); get_zspage_mapping(zspage, &class_idx, &fg); mapping = page_mapping(page); pool = mapping->private_data; class = pool->size_class[class_idx]; spin_lock(&class->lock); dec_zspage_isolation(zspage); if (!is_zspage_isolated(zspage)) { /* * Due to page_lock, we cannot free zspage immediately * so let's defer. */ putback_zspage_deferred(pool, class, zspage); zs_pool_dec_isolated(pool); } spin_unlock(&class->lock); } static const struct address_space_operations zsmalloc_aops = { .isolate_page = zs_page_isolate, .migratepage = zs_page_migrate, .putback_page = zs_page_putback, }; static int zs_register_migration(struct zs_pool *pool) { pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb); if (IS_ERR(pool->inode)) { pool->inode = NULL; return 1; } pool->inode->i_mapping->private_data = pool; pool->inode->i_mapping->a_ops = &zsmalloc_aops; return 0; } static bool pool_isolated_are_drained(struct zs_pool *pool) { return atomic_long_read(&pool->isolated_pages) == 0; } /* Function for resolving migration */ static void wait_for_isolated_drain(struct zs_pool *pool) { /* * We're in the process of destroying the pool, so there are no * active allocations. zs_page_isolate() fails for completely free * zspages, so we need only wait for the zs_pool's isolated * count to hit zero. */ wait_event(pool->migration_wait, pool_isolated_are_drained(pool)); } static void zs_unregister_migration(struct zs_pool *pool) { pool->destroying = true; /* * We need a memory barrier here to ensure global visibility of * pool->destroying. Thus pool->isolated pages will either be 0 in which * case we don't care, or it will be > 0 and pool->destroying will * ensure that we wake up once isolation hits 0. */ smp_mb(); wait_for_isolated_drain(pool); /* This can block */ flush_work(&pool->free_work); iput(pool->inode); } /* * Caller should hold page_lock of all pages in the zspage * In here, we cannot use zspage meta data. */ static void async_free_zspage(struct work_struct *work) { int i; struct size_class *class; unsigned int class_idx; enum fullness_group fullness; struct zspage *zspage, *tmp; LIST_HEAD(free_pages); struct zs_pool *pool = container_of(work, struct zs_pool, free_work); for (i = 0; i < ZS_SIZE_CLASSES; i++) { class = pool->size_class[i]; if (class->index != i) continue; spin_lock(&class->lock); list_splice_init(&class->fullness_list[ZS_EMPTY], &free_pages); spin_unlock(&class->lock); } list_for_each_entry_safe(zspage, tmp, &free_pages, list) { list_del(&zspage->list); lock_zspage(zspage); get_zspage_mapping(zspage, &class_idx, &fullness); VM_BUG_ON(fullness != ZS_EMPTY); class = pool->size_class[class_idx]; spin_lock(&class->lock); __free_zspage(pool, pool->size_class[class_idx], zspage); spin_unlock(&class->lock); } }; static void kick_deferred_free(struct zs_pool *pool) { schedule_work(&pool->free_work); } static void init_deferred_free(struct zs_pool *pool) { INIT_WORK(&pool->free_work, async_free_zspage); } static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) { struct page *page = get_first_page(zspage); do { WARN_ON(!trylock_page(page)); __SetPageMovable(page, pool->inode->i_mapping); unlock_page(page); } while ((page = get_next_page(page)) != NULL); } #endif /* * * Based on the number of unused allocated objects calculate * and return the number of pages that we can free. */ static unsigned long zs_can_compact(struct size_class *class) { unsigned long obj_wasted; unsigned long obj_allocated = zs_stat_get(class, OBJ_ALLOCATED); unsigned long obj_used = zs_stat_get(class, OBJ_USED); if (obj_allocated <= obj_used) return 0; obj_wasted = obj_allocated - obj_used; obj_wasted /= class->objs_per_zspage; return obj_wasted * class->pages_per_zspage; } static unsigned long __zs_compact(struct zs_pool *pool, struct size_class *class) { struct zs_compact_control cc; struct zspage *src_zspage; struct zspage *dst_zspage = NULL; unsigned long pages_freed = 0; spin_lock(&class->lock); while ((src_zspage = isolate_zspage(class, true))) { if (!zs_can_compact(class)) break; cc.obj_idx = 0; cc.s_page = get_first_page(src_zspage); while ((dst_zspage = isolate_zspage(class, false))) { cc.d_page = get_first_page(dst_zspage); /* * If there is no more space in dst_page, resched * and see if anyone had allocated another zspage. */ if (!migrate_zspage(pool, class, &cc)) break; putback_zspage(class, dst_zspage); } /* Stop if we couldn't find slot */ if (dst_zspage == NULL) break; putback_zspage(class, dst_zspage); if (putback_zspage(class, src_zspage) == ZS_EMPTY) { free_zspage(pool, class, src_zspage); pages_freed += class->pages_per_zspage; } spin_unlock(&class->lock); cond_resched(); spin_lock(&class->lock); } if (src_zspage) putback_zspage(class, src_zspage); spin_unlock(&class->lock); return pages_freed; } unsigned long zs_compact(struct zs_pool *pool) { int i; struct size_class *class; unsigned long pages_freed = 0; for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) { class = pool->size_class[i]; if (!class) continue; if (class->index != i) continue; pages_freed += __zs_compact(pool, class); } atomic_long_add(pages_freed, &pool->stats.pages_compacted); return pages_freed; } EXPORT_SYMBOL_GPL(zs_compact); void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats) { memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats)); } EXPORT_SYMBOL_GPL(zs_pool_stats); static unsigned long zs_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc) { unsigned long pages_freed; struct zs_pool *pool = container_of(shrinker, struct zs_pool, shrinker); /* * Compact classes and calculate compaction delta. * Can run concurrently with a manually triggered * (by user) compaction. */ pages_freed = zs_compact(pool); return pages_freed ? pages_freed : SHRINK_STOP; } static unsigned long zs_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc) { int i; struct size_class *class; unsigned long pages_to_free = 0; struct zs_pool *pool = container_of(shrinker, struct zs_pool, shrinker); for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) { class = pool->size_class[i]; if (!class) continue; if (class->index != i) continue; pages_to_free += zs_can_compact(class); } return pages_to_free; } static void zs_unregister_shrinker(struct zs_pool *pool) { unregister_shrinker(&pool->shrinker); } static int zs_register_shrinker(struct zs_pool *pool) { pool->shrinker.scan_objects = zs_shrinker_scan; pool->shrinker.count_objects = zs_shrinker_count; pool->shrinker.batch = 0; pool->shrinker.seeks = DEFAULT_SEEKS; return register_shrinker(&pool->shrinker); } /** * zs_create_pool - Creates an allocation pool to work from. * @name: pool name to be created * * 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(const char *name) { int i; struct zs_pool *pool; struct size_class *prev_class = NULL; pool = kzalloc(sizeof(*pool), GFP_KERNEL); if (!pool) return NULL; init_deferred_free(pool); pool->name = kstrdup(name, GFP_KERNEL); if (!pool->name) goto err; #ifdef CONFIG_COMPACTION init_waitqueue_head(&pool->migration_wait); #endif if (create_cache(pool)) goto err; /* * Iterate reversely, 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; int objs_per_zspage; struct size_class *class; int fullness = 0; 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); objs_per_zspage = pages_per_zspage * PAGE_SIZE / size; /* * We iterate from biggest down to smallest classes, * so huge_class_size holds the size of the first huge * class. Any object bigger than or equal to that will * endup in the huge class. */ if (pages_per_zspage != 1 && objs_per_zspage != 1 && !huge_class_size) { huge_class_size = size; /* * The object uses ZS_HANDLE_SIZE bytes to store the * handle. We need to subtract it, because zs_malloc() * unconditionally adds handle size before it performs * size class search - so object may be smaller than * huge class size, yet it still can end up in the huge * class because it grows by ZS_HANDLE_SIZE extra bytes * right before class lookup. */ huge_class_size -= (ZS_HANDLE_SIZE - 1); } /* * 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, pages_per_zspage, objs_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; class->objs_per_zspage = objs_per_zspage; spin_lock_init(&class->lock); pool->size_class[i] = class; for (fullness = ZS_EMPTY; fullness < NR_ZS_FULLNESS; fullness++) INIT_LIST_HEAD(&class->fullness_list[fullness]); prev_class = class; } /* debug only, don't abort if it fails */ zs_pool_stat_create(pool, name); if (zs_register_migration(pool)) goto err; /* * Not critical since shrinker is only used to trigger internal * defragmentation of the pool which is pretty optional thing. If * registration fails we still can use the pool normally and user can * trigger compaction manually. Thus, ignore return code. */ zs_register_shrinker(pool); 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_unregister_shrinker(pool); zs_unregister_migration(pool); 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 = ZS_EMPTY; fg < NR_ZS_FULLNESS; fg++) { if (!list_empty(&class->fullness_list[fg])) { pr_info("Freeing non-empty class with size %db, fullness group %d\n", class->size, fg); } } kfree(class); } destroy_cache(pool); kfree(pool->name); kfree(pool); } EXPORT_SYMBOL_GPL(zs_destroy_pool); static int __init zs_init(void) { int ret; ret = zsmalloc_mount(); if (ret) goto out; ret = cpuhp_setup_state(CPUHP_MM_ZS_PREPARE, "mm/zsmalloc:prepare", zs_cpu_prepare, zs_cpu_dead); if (ret) goto hp_setup_fail; #ifdef CONFIG_ZPOOL zpool_register_driver(&zs_zpool_driver); #endif zs_stat_init(); return 0; hp_setup_fail: zsmalloc_unmount(); out: return ret; } static void __exit zs_exit(void) { #ifdef CONFIG_ZPOOL zpool_unregister_driver(&zs_zpool_driver); #endif zsmalloc_unmount(); cpuhp_remove_state(CPUHP_MM_ZS_PREPARE); zs_stat_exit(); } module_init(zs_init); module_exit(zs_exit); MODULE_LICENSE("Dual BSD/GPL"); MODULE_AUTHOR("Nitin Gupta ");