diff options
Diffstat (limited to 'mm/zsmalloc.c')
| -rw-r--r-- | mm/zsmalloc.c | 529 |
1 files changed, 188 insertions, 341 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 0d3b65939016..9152fbde33b5 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -30,6 +30,14 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +/* + * lock ordering: + * page_lock + * pool->migrate_lock + * class->lock + * zspage->lock + */ + #include <linux/module.h> #include <linux/kernel.h> #include <linux/sched.h> @@ -57,6 +65,7 @@ #include <linux/wait.h> #include <linux/pagemap.h> #include <linux/fs.h> +#include <linux/local_lock.h> #define ZSPAGE_MAGIC 0x58 @@ -101,15 +110,6 @@ #define _PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT) /* - * Memory for allocating for handle keeps object position by - * encoding <page, obj_idx> 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 @@ -121,6 +121,7 @@ #define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS) #define OBJ_INDEX_MASK ((_AC(1, UL) << OBJ_INDEX_BITS) - 1) +#define HUGE_BITS 1 #define FULLNESS_BITS 2 #define CLASS_BITS 8 #define ISOLATED_BITS 3 @@ -158,7 +159,7 @@ enum fullness_group { NR_ZS_FULLNESS, }; -enum zs_stat_type { +enum class_stat_type { CLASS_EMPTY, CLASS_ALMOST_EMPTY, CLASS_ALMOST_FULL, @@ -213,22 +214,6 @@ struct size_class { 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. @@ -269,15 +254,14 @@ struct zs_pool { #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 + /* protect page/zspage migration */ + rwlock_t migrate_lock; }; struct zspage { struct { + unsigned int huge:HUGE_BITS; unsigned int fullness:FULLNESS_BITS; unsigned int class:CLASS_BITS + 1; unsigned int isolated:ISOLATED_BITS; @@ -293,17 +277,32 @@ struct zspage { }; struct mapping_area { + local_lock_t lock; 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 */ }; +/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */ +static void SetZsHugePage(struct zspage *zspage) +{ + zspage->huge = 1; +} + +static bool ZsHugePage(struct zspage *zspage) +{ + return zspage->huge; +} + #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 migrate_write_lock(struct zspage *zspage); +static void migrate_write_lock_nested(struct zspage *zspage); +static void migrate_write_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); @@ -315,6 +314,9 @@ 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 migrate_write_lock(struct zspage *zspage) {} +static void migrate_write_lock_nested(struct zspage *zspage) {} +static void migrate_write_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) {} @@ -366,14 +368,10 @@ static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage) kmem_cache_free(pool->zspage_cachep, zspage); } +/* class->lock(which owns the handle) synchronizes races */ 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); + *(unsigned long *)handle = obj; } /* zpool driver */ @@ -455,12 +453,9 @@ 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 DEFINE_PER_CPU(struct mapping_area, zs_map_area) = { + .lock = INIT_LOCAL_LOCK(lock), +}; static __maybe_unused int is_first_page(struct page *page) { @@ -517,6 +512,12 @@ static void get_zspage_mapping(struct zspage *zspage, *class_idx = zspage->class; } +static struct size_class *zspage_class(struct zs_pool *pool, + struct zspage *zspage) +{ + return pool->size_class[zspage->class]; +} + static void set_zspage_mapping(struct zspage *zspage, unsigned int class_idx, enum fullness_group fullness) @@ -543,21 +544,21 @@ static int get_size_class_index(int size) 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, +/* type can be of enum type class_stat_type or fullness_group */ +static inline void class_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, +/* type can be of enum type class_stat_type or fullness_group */ +static inline void class_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 */ +/* type can be of enum type class_stat_type or fullness_group */ static inline unsigned long zs_stat_get(struct size_class *class, int type) { @@ -719,7 +720,7 @@ static void insert_zspage(struct size_class *class, { struct zspage *head; - zs_stat_inc(class, fullness, 1); + class_stat_inc(class, fullness, 1); head = list_first_entry_or_null(&class->fullness_list[fullness], struct zspage, list); /* @@ -741,10 +742,9 @@ static void remove_zspage(struct size_class *class, 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); + class_stat_dec(class, fullness, 1); } /* @@ -767,13 +767,9 @@ static enum fullness_group fix_fullness_group(struct size_class *class, if (newfg == currfg) goto out; - if (!is_zspage_isolated(zspage)) { - remove_zspage(class, zspage, currfg); - insert_zspage(class, zspage, newfg); - } - + remove_zspage(class, zspage, currfg); + insert_zspage(class, zspage, newfg); set_zspage_mapping(zspage, class_idx, newfg); - out: return newfg; } @@ -824,7 +820,9 @@ static struct zspage *get_zspage(struct page *page) static struct page *get_next_page(struct page *page) { - if (unlikely(PageHugeObject(page))) + struct zspage *zspage = get_zspage(page); + + if (unlikely(ZsHugePage(zspage))) return NULL; return (struct page *)page->index; @@ -844,6 +842,12 @@ static void obj_to_location(unsigned long obj, struct page **page, *obj_idx = (obj & OBJ_INDEX_MASK); } +static void obj_to_page(unsigned long obj, struct page **page) +{ + obj >>= OBJ_TAG_BITS; + *page = pfn_to_page(obj >> OBJ_INDEX_BITS); +} + /** * location_to_obj - get obj value encoded from (<page>, <obj_idx>) * @page: page object resides in zspage @@ -865,33 +869,22 @@ static unsigned long handle_to_obj(unsigned long handle) return *(unsigned long *)handle; } -static unsigned long obj_to_head(struct page *page, void *obj) +static bool obj_allocated(struct page *page, void *obj, unsigned long *phandle) { - if (unlikely(PageHugeObject(page))) { + unsigned long handle; + struct zspage *zspage = get_zspage(page); + + if (unlikely(ZsHugePage(zspage))) { VM_BUG_ON_PAGE(!is_first_page(page), page); - return page->index; + handle = 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); -} + handle = *(unsigned long *)obj; -static void pin_tag(unsigned long handle) __acquires(bitlock) -{ - bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle); -} + if (!(handle & OBJ_ALLOCATED_TAG)) + return false; -static void unpin_tag(unsigned long handle) __releases(bitlock) -{ - bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle); + *phandle = handle & ~OBJ_ALLOCATED_TAG; + return true; } static void reset_page(struct page *page) @@ -900,7 +893,6 @@ static void reset_page(struct page *page) ClearPagePrivate(page); set_page_private(page, 0); page_mapcount_reset(page); - ClearPageHugeObject(page); page->index = 0; } @@ -952,7 +944,7 @@ static void __free_zspage(struct zs_pool *pool, struct size_class *class, cache_free_zspage(pool, zspage); - zs_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage); + class_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage); atomic_long_sub(class->pages_per_zspage, &pool->pages_allocated); } @@ -963,6 +955,11 @@ static void free_zspage(struct zs_pool *pool, struct size_class *class, VM_BUG_ON(get_zspage_inuse(zspage)); VM_BUG_ON(list_empty(&zspage->list)); + /* + * Since zs_free couldn't be sleepable, this function cannot call + * lock_page. The page locks trylock_zspage got will be released + * by __free_zspage. + */ if (!trylock_zspage(zspage)) { kick_deferred_free(pool); return; @@ -1042,7 +1039,7 @@ static void create_page_chain(struct size_class *class, struct zspage *zspage, SetPagePrivate(page); if (unlikely(class->objs_per_zspage == 1 && class->pages_per_zspage == 1)) - SetPageHugeObject(page); + SetZsHugePage(zspage); } else { prev_page->index = (unsigned long)page; } @@ -1246,8 +1243,6 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle, 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]; @@ -1260,21 +1255,26 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle, */ BUG_ON(in_interrupt()); - /* From now on, migration cannot move the object */ - pin_tag(handle); - + /* It guarantees it can get zspage from handle safely */ + read_lock(&pool->migrate_lock); obj = handle_to_obj(handle); obj_to_location(obj, &page, &obj_idx); zspage = get_zspage(page); - /* migration cannot move any subpage in this zspage */ + /* + * migration cannot move any zpages in this zspage. Here, class->lock + * is too heavy since callers would take some time until they calls + * zs_unmap_object API so delegate the locking from class to zspage + * which is smaller granularity. + */ migrate_read_lock(zspage); + read_unlock(&pool->migrate_lock); - get_zspage_mapping(zspage, &class_idx, &fg); - class = pool->size_class[class_idx]; + class = zspage_class(pool, zspage); off = (class->size * obj_idx) & ~PAGE_MASK; - area = &get_cpu_var(zs_map_area); + local_lock(&zs_map_area.lock); + area = this_cpu_ptr(&zs_map_area); area->vm_mm = mm; if (off + class->size <= PAGE_SIZE) { /* this object is contained entirely within a page */ @@ -1290,7 +1290,7 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle, ret = __zs_map_object(area, pages, off, class->size); out: - if (likely(!PageHugeObject(page))) + if (likely(!ZsHugePage(zspage))) ret += ZS_HANDLE_SIZE; return ret; @@ -1304,16 +1304,13 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle) 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]; + class = zspage_class(pool, zspage); off = (class->size * obj_idx) & ~PAGE_MASK; area = this_cpu_ptr(&zs_map_area); @@ -1328,10 +1325,9 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle) __zs_unmap_object(area, pages, off, class->size); } - put_cpu_var(zs_map_area); + local_unlock(&zs_map_area.lock); migrate_read_unlock(zspage); - unpin_tag(handle); } EXPORT_SYMBOL_GPL(zs_unmap_object); @@ -1354,17 +1350,19 @@ size_t zs_huge_class_size(struct zs_pool *pool) } EXPORT_SYMBOL_GPL(zs_huge_class_size); -static unsigned long obj_malloc(struct size_class *class, +static unsigned long obj_malloc(struct zs_pool *pool, struct zspage *zspage, unsigned long handle) { int i, nr_page, offset; unsigned long obj; struct link_free *link; + struct size_class *class; struct page *m_page; unsigned long m_offset; void *vaddr; + class = pool->size_class[zspage->class]; handle |= OBJ_ALLOCATED_TAG; obj = get_freeobj(zspage); @@ -1379,7 +1377,7 @@ static unsigned long obj_malloc(struct size_class *class, 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))) + if (likely(!ZsHugePage(zspage))) /* record handle in the header of allocated chunk */ link->handle = handle; else @@ -1388,7 +1386,6 @@ static unsigned long obj_malloc(struct size_class *class, kunmap_atomic(vaddr); mod_zspage_inuse(zspage, 1); - zs_stat_inc(class, OBJ_USED, 1); obj = location_to_obj(m_page, obj); @@ -1424,13 +1421,15 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp) size += ZS_HANDLE_SIZE; class = pool->size_class[get_size_class_index(size)]; + /* class->lock effectively protects the zpage migration */ spin_lock(&class->lock); zspage = find_get_zspage(class); if (likely(zspage)) { - obj = obj_malloc(class, zspage, handle); + obj = obj_malloc(pool, zspage, handle); /* Now move the zspage to another fullness group, if required */ fix_fullness_group(class, zspage); record_obj(handle, obj); + class_stat_inc(class, OBJ_USED, 1); spin_unlock(&class->lock); return handle; @@ -1445,14 +1444,15 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp) } spin_lock(&class->lock); - obj = obj_malloc(class, zspage, handle); + obj = obj_malloc(pool, 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); + class_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage); + class_stat_inc(class, OBJ_USED, 1); /* We completely set up zspage so mark them as movable */ SetZsPageMovable(pool, zspage); @@ -1462,7 +1462,7 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp) } EXPORT_SYMBOL_GPL(zs_malloc); -static void obj_free(struct size_class *class, unsigned long obj) +static void obj_free(int class_size, unsigned long obj) { struct link_free *link; struct zspage *zspage; @@ -1472,18 +1472,20 @@ static void obj_free(struct size_class *class, unsigned long obj) void *vaddr; obj_to_location(obj, &f_page, &f_objidx); - f_offset = (class->size * f_objidx) & ~PAGE_MASK; + 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; + if (likely(!ZsHugePage(zspage))) + link->next = get_freeobj(zspage) << OBJ_TAG_BITS; + else + f_page->index = 0; 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) @@ -1491,42 +1493,33 @@ 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); + /* + * The pool->migrate_lock protects the race with zpage's migration + * so it's safe to get the page from handle. + */ + read_lock(&pool->migrate_lock); obj = handle_to_obj(handle); - obj_to_location(obj, &f_page, &f_objidx); + obj_to_page(obj, &f_page); zspage = get_zspage(f_page); - - migrate_read_lock(zspage); - - get_zspage_mapping(zspage, &class_idx, &fullness); - class = pool->size_class[class_idx]; - + class = zspage_class(pool, zspage); spin_lock(&class->lock); - obj_free(class, obj); + read_unlock(&pool->migrate_lock); + + obj_free(class->size, obj); + class_stat_dec(class, OBJ_USED, 1); fullness = fix_fullness_group(class, zspage); - if (fullness != ZS_EMPTY) { - migrate_read_unlock(zspage); + if (fullness != ZS_EMPTY) 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); + free_zspage(pool, class, zspage); out: - spin_unlock(&class->lock); - unpin_tag(handle); cache_free_handle(pool, handle); } EXPORT_SYMBOL_GPL(zs_free); @@ -1601,7 +1594,6 @@ static void zs_object_copy(struct size_class *class, unsigned long dst, 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; @@ -1611,13 +1603,8 @@ static unsigned long find_alloced_obj(struct size_class *class, 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; - } + if (obj_allocated(page, addr + offset, &handle)) + break; offset += class->size; index++; @@ -1663,25 +1650,16 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class, /* 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); + free_obj = obj_malloc(pool, 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); + obj_free(class->size, used_obj); } /* Remember last position in this iteration */ @@ -1706,7 +1684,6 @@ static struct zspage *isolate_zspage(struct size_class *class, bool source) 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; } @@ -1727,8 +1704,6 @@ static enum fullness_group putback_zspage(struct size_class *class, { 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); @@ -1797,6 +1772,11 @@ static void migrate_write_lock(struct zspage *zspage) write_lock(&zspage->lock); } +static void migrate_write_lock_nested(struct zspage *zspage) +{ + write_lock_nested(&zspage->lock, SINGLE_DEPTH_NESTING); +} + static void migrate_write_unlock(struct zspage *zspage) { write_unlock(&zspage->lock); @@ -1810,35 +1790,10 @@ static void inc_zspage_isolation(struct zspage *zspage) static void dec_zspage_isolation(struct zspage *zspage) { + VM_BUG_ON(zspage->isolated == 0); 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); - /* - * Checking pool->destroying must happen after atomic_long_dec() - * for pool->isolated_pages above. Paired with the smp_mb() in - * zs_unregister_migration(). - */ - smp_mb__after_atomic(); - 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) { @@ -1857,19 +1812,14 @@ static void replace_sub_page(struct size_class *class, struct zspage *zspage, create_page_chain(class, zspage, pages); set_first_obj_offset(newpage, get_first_obj_offset(oldpage)); - if (unlikely(PageHugeObject(oldpage))) + if (unlikely(ZsHugePage(zspage))) 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 @@ -1879,41 +1829,9 @@ static bool zs_page_isolate(struct page *page, isolate_mode_t mode) 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); - } - + migrate_write_lock(zspage); inc_zspage_isolation(zspage); - spin_unlock(&class->lock); + migrate_write_unlock(zspage); return true; } @@ -1923,16 +1841,13 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage, { 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; + int offset; + unsigned long handle; 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 @@ -1945,35 +1860,25 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage, 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); + /* + * The pool migrate_lock protects the race between zpage migration + * and zs_free. + */ + write_lock(&pool->migrate_lock); + zspage = get_zspage(page); + class = zspage_class(pool, zspage); + + /* + * the class lock protects zpage alloc/free in the zspage. + */ 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; - } + /* the migrate_write_lock protects zpage access via zs_map_object */ + migrate_write_lock(zspage); - pos = offset; + offset = get_first_obj_offset(page); 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. @@ -1982,42 +1887,30 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage, memcpy(d_addr, s_addr, PAGE_SIZE); kunmap_atomic(d_addr); - for (addr = s_addr + offset; addr < s_addr + pos; + for (addr = s_addr + offset; addr < s_addr + PAGE_SIZE; addr += class->size) { - head = obj_to_head(page, addr); - if (head & OBJ_ALLOCATED_TAG) { - handle = head & ~OBJ_ALLOCATED_TAG; - BUG_ON(!testpin_tag(handle)); + if (obj_allocated(page, addr, &handle)) { 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); } } + kunmap_atomic(s_addr); 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. + * Since we complete the data copy and set up new zspage structure, + * it's okay to release migration_lock. */ - 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); - } + write_unlock(&pool->migrate_lock); + spin_unlock(&class->lock); + dec_zspage_isolation(zspage); + migrate_write_unlock(zspage); + get_page(newpage); if (page_zone(newpage) != page_zone(page)) { dec_zone_page_state(page, NR_ZSPAGES); inc_zone_page_state(newpage, NR_ZSPAGES); @@ -2025,55 +1918,21 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage, 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; - BUG_ON(!testpin_tag(handle)); - unpin_tag(handle); - } - } - kunmap_atomic(s_addr); - spin_unlock(&class->lock); - migrate_write_unlock(zspage); - return ret; + return MIGRATEPAGE_SUCCESS; } 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); + migrate_write_lock(zspage); 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); + migrate_write_unlock(zspage); } static const struct address_space_operations zsmalloc_aops = { @@ -2095,36 +1954,8 @@ static int zs_register_migration(struct zs_pool *pool) 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); } @@ -2154,7 +1985,6 @@ static void async_free_zspage(struct work_struct *work) spin_unlock(&class->lock); } - list_for_each_entry_safe(zspage, tmp, &free_pages, list) { list_del(&zspage->list); lock_zspage(zspage); @@ -2218,8 +2048,13 @@ static unsigned long __zs_compact(struct zs_pool *pool, struct zspage *dst_zspage = NULL; unsigned long pages_freed = 0; + /* protect the race between zpage migration and zs_free */ + write_lock(&pool->migrate_lock); + /* protect zpage allocation/free */ spin_lock(&class->lock); while ((src_zspage = isolate_zspage(class, true))) { + /* protect someone accessing the zspage(i.e., zs_map_object) */ + migrate_write_lock(src_zspage); if (!zs_can_compact(class)) break; @@ -2228,6 +2063,8 @@ static unsigned long __zs_compact(struct zs_pool *pool, cc.s_page = get_first_page(src_zspage); while ((dst_zspage = isolate_zspage(class, false))) { + migrate_write_lock_nested(dst_zspage); + cc.d_page = get_first_page(dst_zspage); /* * If there is no more space in dst_page, resched @@ -2237,6 +2074,10 @@ static unsigned long __zs_compact(struct zs_pool *pool, break; putback_zspage(class, dst_zspage); + migrate_write_unlock(dst_zspage); + dst_zspage = NULL; + if (rwlock_is_contended(&pool->migrate_lock)) + break; } /* Stop if we couldn't find slot */ @@ -2244,19 +2085,28 @@ static unsigned long __zs_compact(struct zs_pool *pool, break; putback_zspage(class, dst_zspage); + migrate_write_unlock(dst_zspage); + if (putback_zspage(class, src_zspage) == ZS_EMPTY) { + migrate_write_unlock(src_zspage); free_zspage(pool, class, src_zspage); pages_freed += class->pages_per_zspage; - } + } else + migrate_write_unlock(src_zspage); spin_unlock(&class->lock); + write_unlock(&pool->migrate_lock); cond_resched(); + write_lock(&pool->migrate_lock); spin_lock(&class->lock); } - if (src_zspage) + if (src_zspage) { putback_zspage(class, src_zspage); + migrate_write_unlock(src_zspage); + } spin_unlock(&class->lock); + write_unlock(&pool->migrate_lock); return pages_freed; } @@ -2362,15 +2212,12 @@ struct zs_pool *zs_create_pool(const char *name) return NULL; init_deferred_free(pool); + rwlock_init(&pool->migrate_lock); 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; |