Re: [PATCH v4 11/12] zsmalloc: page migration support
From: Minchan Kim
Date: Mon May 02 2016 - 21:13:45 EST
Good morning, Chulmin
On Tue, May 03, 2016 at 08:33:16AM +0900, Chulmin Kim wrote:
> Hello, Minchan!
>
> On 2016ë 04ì 27ì 16:48, Minchan Kim wrote:
> >This patch introduces run-time migration feature for zspage.
> >
> >For migration, VM uses page.lru field so it would be better to not use
> >page.next field for own purpose. For that, firstly, we can get first
> >object offset of the page via runtime calculation instead of
> >page->index so we can use page->index as link for page chaining.
> >In case of huge object, it stores handle rather than page chaining.
> >To identify huge object, we uses PG_owner_priv_1 flag.
> >
> >For migration, it supports three functions
> >
> >* zs_page_isolate
> >
> >It isolates a zspage which includes a subpage VM want to migrate from
> >class so anyone cannot allocate new object from the zspage if it's first
> >isolation on subpages of zspage. Thus, further isolation on other
> >subpages cannot isolate zspage from class list.
> >
> >* zs_page_migrate
> >
> >First of all, it holds write-side zspage->lock to prevent migrate other
> >subpage in zspage. Then, lock all objects in the page VM want to migrate.
> >The reason we should lock all objects in the page is due to race between
> >zs_map_object and zs_page_migrate.
> >
> >zs_map_object zs_page_migrate
> >
> >pin_tag(handle)
> >obj = handle_to_obj(handle)
> >obj_to_location(obj, &page, &obj_idx);
> >
> > write_lock(&zspage->lock)
> > if (!trypin_tag(handle))
> > goto unpin_object
> >
> >zspage = get_zspage(page);
> >read_lock(&zspage->lock);
> >
> >If zs_page_migrate doesn't do trypin_tag, zs_map_object's page can
> >be stale so go crash.
> >
> >If it locks all of objects successfully, it copies content from old page
> >create new one, finally, create new page chain with new page.
> >If it's last isolated page in the zspage, put the zspage back to class.
> >
> >* zs_page_putback
> >
> >It returns isolated zspage to right fullness_group list if it fails to
> >migrate a page.
> >
> >Lastly, this patch introduces asynchronous zspage free. The reason
> >we need it is we need page_lock to clear PG_movable but unfortunately,
> >zs_free path should be atomic so the apporach is try to grab page_lock
> >with preemption disabled. If it got page_lock of all of pages
> >successfully, it can free zspage in the context. Otherwise, it queues
> >the free request and free zspage via workqueue in process context.
> >
> >Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> >Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> >---
> > include/uapi/linux/magic.h | 1 +
> > mm/zsmalloc.c | 552 +++++++++++++++++++++++++++++++++++++++------
> > 2 files changed, 487 insertions(+), 66 deletions(-)
> >
> >diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
> >index e1fbe72c39c0..93b1affe4801 100644
> >--- a/include/uapi/linux/magic.h
> >+++ b/include/uapi/linux/magic.h
> >@@ -79,5 +79,6 @@
> > #define NSFS_MAGIC 0x6e736673
> > #define BPF_FS_MAGIC 0xcafe4a11
> > #define BALLOON_KVM_MAGIC 0x13661366
> >+#define ZSMALLOC_MAGIC 0x58295829
> >
> > #endif /* __LINUX_MAGIC_H__ */
> >diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> >index 8d82e44c4644..042793015ecf 100644
> >--- a/mm/zsmalloc.c
> >+++ b/mm/zsmalloc.c
> >@@ -17,15 +17,14 @@
> > *
> > * Usage of struct page fields:
> > * page->private: points to zspage
> >- * page->index: offset of the first object starting in this page.
> >- * For the first page, this is always 0, so we use this field
> >- * to store handle for huge object.
> >- * page->next: links together all component pages of a zspage
> >+ * page->freelist: links together all component pages of a zspage
> >+ * For the huge page, this is always 0, so we use this field
> >+ * to store handle.
> > *
> > * Usage of struct page flags:
> > * PG_private: identifies the first component page
> > * PG_private2: identifies the last component page
> >- *
> >+ * PG_owner_priv_1: indentifies the huge component page
> > */
> >
> > #include <linux/module.h>
> >@@ -47,6 +46,10 @@
> > #include <linux/debugfs.h>
> > #include <linux/zsmalloc.h>
> > #include <linux/zpool.h>
> >+#include <linux/mount.h>
> >+#include <linux/migrate.h>
> >+
> >+#define ZSPAGE_MAGIC 0x58
> >
> > /*
> > * This must be power of 2 and greater than of equal to sizeof(link_free).
> >@@ -128,8 +131,33 @@
> > * ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
> > * (reason above)
> > */
> >+
> >+/*
> >+ * A zspage's class index and fullness group
> >+ * are encoded in its (first)page->mapping
> >+ */
> >+#define FULLNESS_BITS 2
> >+#define CLASS_BITS 8
> >+#define ISOLATED_BITS 3
> >+#define MAGIC_VAL_BITS 8
> >+
> >+
> > #define ZS_SIZE_CLASS_DELTA (PAGE_SIZE >> CLASS_BITS)
> >
> >+struct zspage {
> >+ struct {
> >+ unsigned int fullness:FULLNESS_BITS;
> >+ unsigned int class:CLASS_BITS;
> >+ 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 */
> >+ rwlock_t lock;
> >+};
> >+
> > /*
> > * We do not maintain any list for completely empty or full pages
> > */
> >@@ -161,6 +189,8 @@ struct zs_size_stat {
> > static struct dentry *zs_stat_root;
> > #endif
> >
> >+static struct vfsmount *zsmalloc_mnt;
> >+
> > /*
> > * number of size_classes
> > */
> >@@ -243,24 +273,10 @@ struct zs_pool {
> > #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 FULLNESS_BITS 2
> >-#define CLASS_BITS 8
> >-
> >-struct zspage {
> >- struct {
> >- unsigned int fullness:FULLNESS_BITS;
> >- unsigned int class:CLASS_BITS;
> >- };
> >- unsigned int inuse;
> >- unsigned int freeobj;
> >- struct page *first_page;
> >- struct list_head list; /* fullness list */
> >+ struct inode *inode;
> >+ spinlock_t free_lock;
> >+ struct work_struct free_work;
> >+ struct list_head free_zspage;
> > };
> >
> > struct mapping_area {
> >@@ -312,8 +328,11 @@ static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
> > struct zspage *zspage;
> >
> > zspage = kmem_cache_alloc(pool->zspage_cachep, flags & ~__GFP_HIGHMEM);
> >- if (zspage)
> >+ if (zspage) {
> > memset(zspage, 0, sizeof(struct zspage));
> >+ zspage->magic = ZSPAGE_MAGIC;
> >+ rwlock_init(&zspage->lock);
>
> + INIT_LIST_HEAD(&zspage->list);
>
> If there is no special intention here,
> I think we need the list initialization.
Intention was that I just watned to add unncessary instruction there
although it was not expensive. :)
>
> There are some functions checking "list_empty(&zspage->list)".
> and they might be executed before the list initialization in rare cases.
There are two places now.
1. zspage_isolate
It's okay because zs_page_isolate checks get_zspage_inuse under
class->lock while alloc_zspage adds newly created zspage to list
under class->lock with increasing used object count.
2. free_zspage
It's okay because every zspage passed free_zspage should
remove from list and remove_zspage has list_del_init and
the used object in the zspage should be zero so zs_page_isolate
cannot pick it up.
> (AFAIK, the list initialization is being done by insert_zspage(),etc.)
> I guess, checking the uninitialized list is not intended at all.
You have been great to spot something until now so you are saying
with some clue already and I might miss something. :)
Do you have another scenario to make race problem?
Otherwise, I want to remain as it is because I want to reveal the
problem rather than hiding problems with safe-guard. :)
Thanks for the review, Chulmin!
>
> Thanks!
> Chulmin
>
>
> >+ }
> > return zspage;
> > };
> >
> >@@ -419,11 +438,27 @@ static unsigned int get_maxobj_per_zspage(int size, int pages_per_zspage)
> > /* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
> > static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
> >
> >+static void inc_zspage_isolation(struct zspage *zspage)
> >+{
> >+ zspage->isolated++;
> >+}
> >+
> >+static void dec_zspage_isolation(struct zspage *zspage)
> >+{
> >+ zspage->isolated--;
> >+}
> >+
> >+static int get_zspage_isolation(struct zspage *zspage)
> >+{
> >+ return zspage->isolated;
> >+}
> >+
> > static 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;
> >@@ -439,20 +474,12 @@ static inline void mod_zspage_inuse(struct zspage *zspage, int val)
> > zspage->inuse += val;
> > }
> >
> >-static inline int get_first_obj_offset(struct page *page)
> >+static inline struct page *get_first_page(struct zspage *zspage)
> > {
> >- if (is_first_page(page))
> >- return 0;
> >+ struct page *first_page = zspage->first_page;
> >
> >- return page->index;
> >-}
> >-
> >-static inline void set_first_obj_offset(struct page *page, int offset)
> >-{
> >- if (is_first_page(page))
> >- return;
> >-
> >- page->index = offset;
> >+ VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
> >+ return first_page;
> > }
> >
> > static inline unsigned int get_freeobj(struct zspage *zspage)
> >@@ -469,6 +496,8 @@ static void get_zspage_mapping(struct zspage *zspage,
> > unsigned int *class_idx,
> > enum fullness_group *fullness)
> > {
> >+ VM_BUG_ON(zspage->magic != ZSPAGE_MAGIC);
> >+
> > *fullness = zspage->fullness;
> > *class_idx = zspage->class;
> > }
> >@@ -738,6 +767,7 @@ static void remove_zspage(struct size_class *class,
> > return;
> >
> > VM_BUG_ON(list_empty(&class->fullness_list[fullness]));
> >+ VM_BUG_ON(get_zspage_isolation(zspage));
> >
> > list_del_init(&zspage->list);
> > zs_stat_dec(class, fullness == ZS_ALMOST_EMPTY ?
> >@@ -764,8 +794,10 @@ static enum fullness_group fix_fullness_group(struct size_class *class,
> > if (newfg == currfg)
> > goto out;
> >
> >- remove_zspage(class, zspage, currfg);
> >- insert_zspage(class, zspage, newfg);
> >+ if (!get_zspage_isolation(zspage)) {
> >+ remove_zspage(class, zspage, currfg);
> >+ insert_zspage(class, zspage, newfg);
> >+ }
> > set_zspage_mapping(zspage, class_idx, newfg);
> >
> > out:
> >@@ -808,19 +840,47 @@ static int get_pages_per_zspage(int class_size)
> > return max_usedpc_order;
> > }
> >
> >-static struct page *get_first_page(struct zspage *zspage)
> >+static struct zspage *get_zspage(struct page *page)
> > {
> >- return zspage->first_page;
> >+ struct zspage *zspage = (struct zspage *)page->private;
> >+
> >+ VM_BUG_ON(zspage->magic != ZSPAGE_MAGIC);
> >+ return zspage;
> > }
> >
> >-static struct zspage *get_zspage(struct page *page)
> >+static struct page *get_next_page(struct page *page)
> > {
> >- return (struct zspage *)page->private;
> >+ if (PageOwnerPriv1(page))
> >+ return NULL;
> >+
> >+ return page->freelist;
> > }
> >
> >-static struct page *get_next_page(struct page *page)
> >+/* Get byte offset of first object in the @page */
> >+static int get_first_obj_offset(struct size_class *class,
> >+ struct page *first_page, struct page *page)
> > {
> >- return page->next;
> >+ int pos, bound;
> >+ int page_idx = 0;
> >+ int ofs = 0;
> >+ struct page *cursor = first_page;
> >+
> >+ if (first_page == page)
> >+ goto out;
> >+
> >+ while (page != cursor) {
> >+ page_idx++;
> >+ cursor = get_next_page(cursor);
> >+ }
> >+
> >+ bound = PAGE_SIZE * page_idx;
> >+ pos = (((class->objs_per_zspage * class->size) *
> >+ page_idx / class->pages_per_zspage) / class->size
> >+ ) * class->size;
> >+
> >+ ofs = (pos + class->size) % PAGE_SIZE;
> >+out:
> >+ return ofs;
> > }
> >
> > /**
> >@@ -867,6 +927,11 @@ static unsigned long obj_to_head(struct size_class *class, struct page *page,
> > 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);
> >@@ -884,22 +949,60 @@ static void unpin_tag(unsigned long handle)
> >
> > static void reset_page(struct page *page)
> > {
> >+ __ClearPageMovable(page);
> > clear_bit(PG_private, &page->flags);
> > clear_bit(PG_private_2, &page->flags);
> >+ ClearPageOwnerPriv1(page);
> > set_page_private(page, 0);
> >- page->index = 0;
> >+ page->freelist = NULL;
> > }
> >
> >-static void free_zspage(struct zs_pool *pool, struct zspage *zspage)
> >+/*
> >+ * To prevent zspage destroy during migration, zspage freeing should
> >+ * hold locks of all pages in the zspage.
> >+ */
> >+void lock_zspage(struct zspage *zspage)
> >+{
> >+ struct page *page = get_first_page(zspage);
> >+
> >+ do {
> >+ lock_page(page);
> >+ } while ((page = get_next_page(page)) != NULL);
> >+}
> >+
> >+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 zspage *zspage)
> > {
> > struct page *page, *next;
> >
> > VM_BUG_ON(get_zspage_inuse(zspage));
> >
> >- next = page = zspage->first_page;
> >+ next = page = get_first_page(zspage);
> > do {
> >- next = page->next;
> >+ VM_BUG_ON_PAGE(!PageLocked(page), page);
> >+ next = get_next_page(page);
> > reset_page(page);
> >+ unlock_page(page);
> > put_page(page);
> > page = next;
> > } while (page != NULL);
> >@@ -907,20 +1010,34 @@ static void free_zspage(struct zs_pool *pool, struct zspage *zspage)
> > cache_free_zspage(pool, zspage);
> > }
> >
> >+static void free_zspage(struct zs_pool *pool, struct zspage *zspage)
> >+{
> >+ VM_BUG_ON(get_zspage_inuse(zspage));
> >+
> >+ if (!trylock_zspage(zspage)) {
> >+ spin_lock(&pool->free_lock);
> >+ VM_BUG_ON(!list_empty(&zspage->list));
> >+ list_add(&zspage->list, &pool->free_zspage);
> >+ spin_unlock(&pool->free_lock);
> >+ schedule_work(&pool->free_work);
> >+ return;
> >+ }
> >+
> >+ __free_zspage(pool, 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 = zspage->first_page;
> >+ 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);
> >
> >@@ -952,16 +1069,17 @@ static void init_zspage(struct size_class *class, struct zspage *zspage)
> > set_freeobj(zspage, 0);
> > }
> >
> >-static void create_page_chain(struct zspage *zspage, struct page *pages[],
> >- int nr_pages)
> >+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->next
> >+ * 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
> >@@ -970,20 +1088,43 @@ static void create_page_chain(struct zspage *zspage, struct page *pages[],
> > 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 (class->huge)
> >+ SetPageOwnerPriv1(page);
> > } else {
> >- prev_page->next = page;
> >+ prev_page->freelist = page;
> > }
> >- if (i == nr_pages - 1) {
> >+ if (i == nr_pages - 1)
> > SetPagePrivate2(page);
> >- page->next = NULL;
> >- }
> > prev_page = page;
> > }
> > }
> >
> >+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);
> >+ if (class->huge)
> >+ newpage->index = oldpage->index;
> >+ __SetPageMovable(newpage, page_mapping(oldpage));
> >+}
> >+
> > /*
> > * Allocate a zspage for the given size class
> > */
> >@@ -1010,7 +1151,7 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
> > pages[i] = page;
> > }
> >
> >- create_page_chain(zspage, pages, class->pages_per_zspage);
> >+ create_page_chain(class, zspage, pages);
> > init_zspage(class, zspage);
> >
> > return zspage;
> >@@ -1286,6 +1427,10 @@ void *zs_map_object(struct zs_pool *pool, unsigned long 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 */
> >+ read_lock(&zspage->lock);
> >+
> > get_zspage_mapping(zspage, &class_idx, &fg);
> > class = pool->size_class[class_idx];
> > off = (class->size * obj_idx) & ~PAGE_MASK;
> >@@ -1345,6 +1490,8 @@ 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);
> >+
> >+ read_unlock(&zspage->lock);
> > unpin_tag(handle);
> > }
> > EXPORT_SYMBOL_GPL(zs_unmap_object);
> >@@ -1421,6 +1568,8 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
> > zspage = find_get_zspage(class);
> >
> > if (!zspage) {
> >+ struct page *page;
> >+
> > spin_unlock(&class->lock);
> > zspage = alloc_zspage(pool, class);
> > if (unlikely(!zspage)) {
> >@@ -1432,6 +1581,14 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
> > atomic_long_add(class->pages_per_zspage,
> > &pool->pages_allocated);
> >
> >+ /* We completely set up zspage so mark them as movable */
> >+ 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);
> >+
> > spin_lock(&class->lock);
> > zs_stat_inc(class, OBJ_ALLOCATED, get_maxobj_per_zspage(
> > class->size, class->pages_per_zspage));
> >@@ -1490,6 +1647,8 @@ void zs_free(struct zs_pool *pool, unsigned long handle)
> > obj_to_location(obj, &f_page, &f_objidx);
> > zspage = get_zspage(f_page);
> >
> >+ read_lock(&zspage->lock);
> >+
> > get_zspage_mapping(zspage, &class_idx, &fullness);
> > class = pool->size_class[class_idx];
> >
> >@@ -1501,11 +1660,14 @@ void zs_free(struct zs_pool *pool, unsigned long handle)
> > class->size, class->pages_per_zspage));
> > atomic_long_sub(class->pages_per_zspage,
> > &pool->pages_allocated);
> >+ read_unlock(&zspage->lock);
> > free_zspage(pool, zspage);
> >+ spin_unlock(&class->lock);
> >+ } else {
> >+ read_unlock(&zspage->lock);
> >+ spin_unlock(&class->lock);
> > }
> >- spin_unlock(&class->lock);
> > unpin_tag(handle);
> >-
> > cache_free_handle(pool, handle);
> > }
> > EXPORT_SYMBOL_GPL(zs_free);
> >@@ -1584,8 +1746,9 @@ static unsigned long find_alloced_obj(struct size_class *class,
> > int offset = 0;
> > unsigned long handle = 0;
> > void *addr = kmap_atomic(page);
> >+ struct zspage *zspage = get_zspage(page);
> >
> >- offset = get_first_obj_offset(page);
> >+ offset = get_first_obj_offset(class, get_first_page(zspage), page);
> > offset += class->size * index;
> >
> > while (offset < PAGE_SIZE) {
> >@@ -1681,6 +1844,7 @@ 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(get_zspage_isolation(zspage));
> > remove_zspage(class, zspage, fg[i]);
> > return zspage;
> > }
> >@@ -1701,6 +1865,8 @@ static enum fullness_group putback_zspage(struct size_class *class,
> > {
> > enum fullness_group fullness;
> >
> >+ VM_BUG_ON(get_zspage_isolation(zspage));
> >+
> > fullness = get_fullness_group(class, zspage);
> > insert_zspage(class, zspage, fullness);
> > set_zspage_mapping(zspage, class->index, fullness);
> >@@ -1739,10 +1905,10 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class)
> > break;
> >
> > cc.index = 0;
> >- cc.s_page = src_zspage->first_page;
> >+ cc.s_page = get_first_page(src_zspage);
> >
> > while ((dst_zspage = isolate_zspage(class, false))) {
> >- cc.d_page = dst_zspage->first_page;
> >+ 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.
> >@@ -1859,6 +2025,218 @@ static int zs_register_shrinker(struct zs_pool *pool)
> > return register_shrinker(&pool->shrinker);
> > }
> >
> >+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) && !get_zspage_isolation(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) && !get_zspage_isolation(zspage)) {
> >+ get_zspage_mapping(zspage, &class_idx, &fullness);
> >+ remove_zspage(class, zspage, fullness);
> >+ }
> >+
> >+ inc_zspage_isolation(zspage);
> >+ spin_unlock(&class->lock);
> >+
> >+ return true;
> >+}
> >+
> >+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;
> >+
> >+ 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 */
> >+ write_lock(&zspage->lock);
> >+ get_zspage_mapping(zspage, &class_idx, &fullness);
> >+ pool = mapping->private_data;
> >+ class = pool->size_class[class_idx];
> >+ offset = get_first_obj_offset(class, get_first_page(zspage), page);
> >+
> >+ spin_lock(&class->lock);
> >+ if (!get_zspage_inuse(zspage))
> >+ goto unlock_class;
> >+
> >+ pos = offset;
> >+ s_addr = kmap_atomic(page);
> >+ while (pos < PAGE_SIZE) {
> >+ head = obj_to_head(class, 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(class, 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 (!get_zspage_isolation(zspage))
> >+ putback_zspage(class, zspage);
> >+
> >+ 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(class, page, addr);
> >+ if (head & OBJ_ALLOCATED_TAG) {
> >+ handle = head & ~OBJ_ALLOCATED_TAG;
> >+ if (!testpin_tag(handle))
> >+ BUG();
> >+ unpin_tag(handle);
> >+ }
> >+ }
> >+ kunmap_atomic(s_addr);
> >+unlock_class:
> >+ spin_unlock(&class->lock);
> >+ write_unlock(&zspage->lock);
> >+
> >+ return ret;
> >+}
> >+
> >+void zs_page_putback(struct page *page)
> >+{
> >+ struct zs_pool *pool;
> >+ struct size_class *class;
> >+ int class_idx;
> >+ enum fullness_group dummy;
> >+ 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, &dummy);
> >+ mapping = page_mapping(page);
> >+ pool = mapping->private_data;
> >+ class = pool->size_class[class_idx];
> >+
> >+ spin_lock(&class->lock);
> >+ dec_zspage_isolation(zspage);
> >+ if (!get_zspage_isolation(zspage))
> >+ putback_zspage(class, zspage);
> >+ spin_unlock(&class->lock);
> >+}
> >+
> >+const struct address_space_operations zsmalloc_aops = {
> >+ .isolate_page = zs_page_isolate,
> >+ .migratepage = zs_page_migrate,
> >+ .putback_page = zs_page_putback,
> >+};
> >+
> >+/*
> >+ * 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)
> >+{
> >+ struct zspage *zspage, *tmp;
> >+ LIST_HEAD(free_pages);
> >+ struct zs_pool *pool = container_of(work, struct zs_pool,
> >+ free_work);
> >+
> >+ spin_lock(&pool->free_lock);
> >+ list_splice_init(&pool->free_zspage, &free_pages);
> >+ spin_unlock(&pool->free_lock);
> >+
> >+ list_for_each_entry_safe(zspage, tmp, &free_pages, list) {
> >+ list_del(&zspage->list);
> >+ lock_zspage(zspage);
> >+ __free_zspage(pool, zspage);
> >+ }
> >+};
> >+
> > /**
> > * zs_create_pool - Creates an allocation pool to work from.
> > * @flags: allocation flags used to allocate pool metadata
> >@@ -1879,6 +2257,10 @@ struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
> > if (!pool)
> > return NULL;
> >
> >+ INIT_WORK(&pool->free_work, async_free_zspage);
> >+ INIT_LIST_HEAD(&pool->free_zspage);
> >+ spin_lock_init(&pool->free_lock);
> >+
> > pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *),
> > GFP_KERNEL);
> > if (!pool->size_class) {
> >@@ -1944,11 +2326,21 @@ struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
> > prev_class = class;
> > }
> >
> >+ INIT_LIST_HEAD(&pool->free_zspage);
> > pool->flags = flags;
> >
> > if (zs_pool_stat_create(pool, name))
> > goto err;
> >
> >+ pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
> >+ if (IS_ERR(pool->inode)) {
> >+ pool->inode = NULL;
> >+ goto err;
> >+ }
> >+
> >+ pool->inode->i_mapping->a_ops = &zsmalloc_aops;
> >+ pool->inode->i_mapping->private_data = pool;
> >+
> > /*
> > * Not critical, we still can use the pool
> > * and user can trigger compaction manually.
> >@@ -1967,7 +2359,11 @@ void zs_destroy_pool(struct zs_pool *pool)
> > {
> > int i;
> >
> >+ flush_work(&pool->free_work);
> >+
> > zs_unregister_shrinker(pool);
> >+ if (pool->inode)
> >+ iput(pool->inode);
> > zs_pool_stat_destroy(pool);
> >
> > for (i = 0; i < zs_size_classes; i++) {
> >@@ -1996,10 +2392,33 @@ void zs_destroy_pool(struct zs_pool *pool)
> > }
> > EXPORT_SYMBOL_GPL(zs_destroy_pool);
> >
> >+static struct dentry *zs_mount(struct file_system_type *fs_type,
> >+ int flags, const char *dev_name, void *data)
> >+{
> >+ static const struct dentry_operations ops = {
> >+ .d_dname = simple_dname,
> >+ };
> >+
> >+ return mount_pseudo(fs_type, "zsmalloc:", NULL, &ops, ZSMALLOC_MAGIC);
> >+}
> >+
> >+static struct file_system_type zsmalloc_fs = {
> >+ .name = "zsmalloc",
> >+ .mount = zs_mount,
> >+ .kill_sb = kill_anon_super,
> >+};
> >+
> > static int __init zs_init(void)
> > {
> >- int ret = zs_register_cpu_notifier();
> >+ int ret;
> >
> >+ zsmalloc_mnt = kern_mount(&zsmalloc_fs);
> >+ if (IS_ERR(zsmalloc_mnt)) {
> >+ ret = PTR_ERR(zsmalloc_mnt);
> >+ goto out;
> >+ }
> >+
> >+ ret = zs_register_cpu_notifier();
> > if (ret)
> > goto notifier_fail;
> >
> >@@ -2022,7 +2441,8 @@ static int __init zs_init(void)
> > #endif
> > notifier_fail:
> > zs_unregister_cpu_notifier();
> >-
> >+ kern_unmount(zsmalloc_mnt);
> >+out:
> > return ret;
> > }
> >
> >
>
> --
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