The patch titled
Subject: zsmalloc: migrate head page of zspage
has been added to the -mm tree. Its filename is
zsmalloc-migrate-head-page-of-zspage.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zsmalloc-migrate-head-page-of-zspage.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zsmalloc-migrate-head-page-of-zspage.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: zsmalloc: migrate head page of zspage
This patch introduces run-time migration feature for zspage. To begin
with, it supports only head page migration for easy review(later patches
will support tail page migration).
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. IOW,
allocation freeze
* zs_page_migrate
First of all, it freezes zspage to prevent zspage destrunction so anyone
cannot free object. Then, It copies content from oldpage to newpage and
create new page-chain with new page. If it was successful, drop the
refcount of old page to free and putback new zspage to right data
structure of zsmalloc. Lastly, unfreeze zspages so we allows object
allocation/free from now on.
* zs_page_putback
It returns isolated zspage to right fullness_group list if it fails to
migrate a page.
NOTE: A hurdle to support migration is that destroying zspage while
migration is going on. Once a zspage is isolated, anyone cannot allocate
object from the zspage but can deallocate object freely so a zspage could
be destroyed until all of objects in zspage are freezed to prevent
deallocation. The problem is large window betwwen zs_page_isolate and
freeze_zspage in zs_page_migrate so the zspage could be destroyed.
A easy approach to solve the problem is that object freezing in
zs_page_isolate but it has a drawback that any object cannot be
deallocated until migration fails after isolation. However, There is
large time gab between isolation and migration so any object freeing in
other CPU should spin by pin_tag which would cause big latency. So, this
patch introduces lock_zspage which holds PG_lock of all pages in a zspage
right before freeing the zspage. VM migration locks the page, too right
before calling ->migratepage so such race doesn't exist any more.
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Cc: Rafael Aquini <aquini@xxxxxxxxxx>
Cc: Russ Knize <rknize@xxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Gioh Kim <gi-oh.kim@xxxxxxxxxxxxxxxx>
Cc: Sangseok Lee <sangseok.lee@xxxxxxx>
Cc: Chan Gyun Jeong <chan.jeong@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: YiPing Xu <xuyiping@xxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/magic.h | 1
mm/zsmalloc.c | 332 +++++++++++++++++++++++++++++++++--
2 files changed, 318 insertions(+), 15 deletions(-)
diff -puN include/uapi/linux/magic.h~zsmalloc-migrate-head-page-of-zspage include/uapi/linux/magic.h
--- a/include/uapi/linux/magic.h~zsmalloc-migrate-head-page-of-zspage
+++ a/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 -puN mm/zsmalloc.c~zsmalloc-migrate-head-page-of-zspage mm/zsmalloc.c
--- a/mm/zsmalloc.c~zsmalloc-migrate-head-page-of-zspage
+++ a/mm/zsmalloc.c
@@ -56,6 +56,8 @@
#include <linux/debugfs.h>
#include <linux/zsmalloc.h>
#include <linux/zpool.h>
+#include <linux/mount.h>
+#include <linux/migrate.h>
/*
* This must be power of 2 and greater than of equal to sizeof(link_free).
@@ -182,6 +184,8 @@ struct zs_size_stat {
static struct dentry *zs_stat_root;
#endif
+static struct vfsmount *zsmalloc_mnt;
+
/*
* number of size_classes
*/
@@ -263,6 +267,7 @@ struct zs_pool {
#ifdef CONFIG_ZSMALLOC_STAT
struct dentry *stat_dentry;
#endif
+ struct inode *inode;
};
struct zs_meta {
@@ -412,6 +417,29 @@ static int is_last_page(struct page *pag
return PagePrivate2(page);
}
+/*
+ * Indicate that whether zspage is isolated for page migration.
+ * Protected by size_class lock
+ */
+static void SetZsPageIsolate(struct page *first_page)
+{
+ VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
+ SetPageUptodate(first_page);
+}
+
+static int ZsPageIsolate(struct page *first_page)
+{
+ VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
+
+ return PageUptodate(first_page);
+}
+
+static void ClearZsPageIsolate(struct page *first_page)
+{
+ VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
+ ClearPageUptodate(first_page);
+}
+
static int get_zspage_inuse(struct page *first_page)
{
struct zs_meta *m;
@@ -783,8 +811,11 @@ static enum fullness_group fix_fullness_
if (newfg == currfg)
goto out;
- remove_zspage(class, currfg, first_page);
- insert_zspage(class, newfg, first_page);
+ /* Later, putback will insert page to right list */
+ if (!ZsPageIsolate(first_page)) {
+ remove_zspage(class, currfg, first_page);
+ insert_zspage(class, newfg, first_page);
+ }
set_zspage_mapping(first_page, class_idx, newfg);
out:
@@ -950,12 +981,31 @@ static void unpin_tag(unsigned long hand
static void reset_page(struct page *page)
{
+ if (!PageIsolated(page))
+ __ClearPageMovable(page);
+ ClearPageIsolated(page);
clear_bit(PG_private, &page->flags);
clear_bit(PG_private_2, &page->flags);
set_page_private(page, 0);
page->freelist = NULL;
}
+/**
+ * lock_zspage - lock all pages in the zspage
+ * @first_page: head page of the zspage
+ *
+ * To prevent destroy during migration, zspage freeing should
+ * hold locks of all pages in a zspage
+ */
+void lock_zspage(struct page *first_page)
+{
+ struct page *cursor = first_page;
+
+ do {
+ while (!trylock_page(cursor));
+ } while ((cursor = get_next_page(cursor)) != NULL);
+}
+
static void free_zspage(struct zs_pool *pool, struct page *first_page)
{
struct page *nextp, *tmp, *head_extra;
@@ -963,26 +1013,31 @@ static void free_zspage(struct zs_pool *
VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
VM_BUG_ON_PAGE(get_zspage_inuse(first_page), first_page);
+ lock_zspage(first_page);
head_extra = (struct page *)page_private(first_page);
- reset_page(first_page);
- __free_page(first_page);
-
/* zspage with only 1 system page */
if (!head_extra)
- return;
+ goto out;
list_for_each_entry_safe(nextp, tmp, &head_extra->lru, lru) {
list_del(&nextp->lru);
reset_page(nextp);
- __free_page(nextp);
+ unlock_page(nextp);
+ put_page(nextp);
}
reset_page(head_extra);
- __free_page(head_extra);
+ unlock_page(head_extra);
+ put_page(head_extra);
+out:
+ reset_page(first_page);
+ unlock_page(first_page);
+ put_page(first_page);
}
/* Initialize a newly allocated zspage */
-static void init_zspage(struct size_class *class, struct page *first_page)
+static void init_zspage(struct size_class *class, struct page *first_page,
+ struct address_space *mapping)
{
int freeobj = 1;
unsigned long off = 0;
@@ -991,6 +1046,9 @@ static void init_zspage(struct size_clas
first_page->freelist = NULL;
INIT_LIST_HEAD(&first_page->lru);
set_zspage_inuse(first_page, 0);
+ BUG_ON(!trylock_page(first_page));
+ __SetPageMovable(first_page, mapping);
+ unlock_page(first_page);
while (page) {
struct page *next_page;
@@ -1065,10 +1123,45 @@ static void create_page_chain(struct pag
}
}
+static void replace_sub_page(struct size_class *class, struct page *first_page,
+ struct page *newpage, struct page *oldpage)
+{
+ struct page *page;
+ struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL,};
+ int idx = 0;
+
+ page = first_page;
+ do {
+ if (page == oldpage)
+ pages[idx] = newpage;
+ else
+ pages[idx] = page;
+ idx++;
+ } while ((page = get_next_page(page)) != NULL);
+
+ create_page_chain(pages, class->pages_per_zspage);
+
+ if (is_first_page(oldpage)) {
+ enum fullness_group fg;
+ int class_idx;
+
+ SetZsPageIsolate(newpage);
+ get_zspage_mapping(oldpage, &class_idx, &fg);
+ set_zspage_mapping(newpage, class_idx, fg);
+ set_freeobj(newpage, get_freeobj(oldpage));
+ set_zspage_inuse(newpage, get_zspage_inuse(oldpage));
+ if (class->huge)
+ set_page_private(newpage, page_private(oldpage));
+ }
+
+ __SetPageMovable(newpage, oldpage->mapping);
+}
+
/*
* Allocate a zspage for the given size class
*/
-static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
+static struct page *alloc_zspage(struct zs_pool *pool,
+ struct size_class *class)
{
int i;
struct page *first_page = NULL;
@@ -1088,7 +1181,7 @@ static struct page *alloc_zspage(struct
for (i = 0; i < class->pages_per_zspage; i++) {
struct page *page;
- page = alloc_page(flags);
+ page = alloc_page(pool->flags);
if (!page) {
while (--i >= 0)
__free_page(pages[i]);
@@ -1100,7 +1193,7 @@ static struct page *alloc_zspage(struct
create_page_chain(pages, class->pages_per_zspage);
first_page = pages[0];
- init_zspage(class, first_page);
+ init_zspage(class, first_page, pool->inode->i_mapping);
return first_page;
}
@@ -1499,7 +1592,7 @@ unsigned long zs_malloc(struct zs_pool *
if (!first_page) {
spin_unlock(&class->lock);
- first_page = alloc_zspage(class, pool->flags);
+ first_page = alloc_zspage(pool, class);
if (unlikely(!first_page)) {
free_handle(pool, handle);
return 0;
@@ -1559,6 +1652,7 @@ void zs_free(struct zs_pool *pool, unsig
if (unlikely(!handle))
return;
+ /* Once handle is pinned, page|object migration cannot work */
pin_tag(handle);
obj = handle_to_obj(handle);
obj_to_location(obj, &f_page, &f_objidx);
@@ -1714,6 +1808,9 @@ static enum fullness_group putback_zspag
{
enum fullness_group fullness;
+ VM_BUG_ON_PAGE(!list_empty(&first_page->lru), first_page);
+ VM_BUG_ON_PAGE(ZsPageIsolate(first_page), first_page);
+
fullness = get_fullness_group(class, first_page);
insert_zspage(class, fullness, first_page);
set_zspage_mapping(first_page, class->index, fullness);
@@ -2059,6 +2156,173 @@ static int zs_register_shrinker(struct z
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 page *first_page;
+
+ /*
+ * The page is locked so it couldn't be destroyed.
+ * For detail, look at lock_zspage in free_zspage.
+ */
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(PageIsolated(page), page);
+ /*
+ * In this implementation, it allows only first page migration.
+ */
+ VM_BUG_ON_PAGE(!is_first_page(page), page);
+ first_page = page;
+
+ /*
+ * Without class lock, fullness is meaningless while constant
+ * class_idx is okay. We will get it under class lock at below,
+ * again.
+ */
+ get_zspage_mapping(first_page, &class_idx, &fullness);
+ pool = page->mapping->private_data;
+ class = pool->size_class[class_idx];
+
+ if (!spin_trylock(&class->lock))
+ return false;
+
+ get_zspage_mapping(first_page, &class_idx, &fullness);
+ remove_zspage(class, fullness, first_page);
+ SetZsPageIsolate(first_page);
+ SetPageIsolated(page);
+ 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 page *first_page;
+ void *s_addr, *d_addr, *addr;
+ int ret = -EBUSY;
+ int offset = 0;
+ int freezed = 0;
+
+ VM_BUG_ON_PAGE(!PageMovable(page), page);
+ VM_BUG_ON_PAGE(!PageIsolated(page), page);
+
+ first_page = page;
+ get_zspage_mapping(first_page, &class_idx, &fullness);
+ pool = page->mapping->private_data;
+ class = pool->size_class[class_idx];
+
+ /*
+ * Get stable fullness under class->lock
+ */
+ if (!spin_trylock(&class->lock))
+ return ret;
+
+ get_zspage_mapping(first_page, &class_idx, &fullness);
+ if (get_zspage_inuse(first_page) == 0)
+ goto out_class_unlock;
+
+ freezed = freeze_zspage(class, first_page);
+ if (freezed != get_zspage_inuse(first_page))
+ goto out_unfreeze;
+
+ /* copy contents from page to newpage */
+ s_addr = kmap_atomic(page);
+ d_addr = kmap_atomic(newpage);
+ memcpy(d_addr, s_addr, PAGE_SIZE);
+ kunmap_atomic(d_addr);
+ kunmap_atomic(s_addr);
+
+ if (!is_first_page(page))
+ offset = page->index;
+
+ addr = kmap_atomic(page);
+ do {
+ unsigned long handle;
+ unsigned long head;
+ unsigned long new_obj, old_obj;
+ unsigned long obj_idx;
+ struct page *dummy;
+
+ head = obj_to_head(class, page, addr + offset);
+ 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 = location_to_obj(newpage, obj_idx);
+ new_obj |= BIT(HANDLE_PIN_BIT);
+ record_obj(handle, new_obj);
+ }
+ offset += class->size;
+ } while (offset < PAGE_SIZE);
+ kunmap_atomic(addr);
+
+ replace_sub_page(class, first_page, newpage, page);
+ first_page = newpage;
+ get_page(newpage);
+ VM_BUG_ON_PAGE(get_fullness_group(class, first_page) ==
+ ZS_EMPTY, first_page);
+ ClearZsPageIsolate(first_page);
+ putback_zspage(class, first_page);
+
+ /* Migration complete. Free old page */
+ ClearPageIsolated(page);
+ reset_page(page);
+ put_page(page);
+ ret = MIGRATEPAGE_SUCCESS;
+
+out_unfreeze:
+ unfreeze_zspage(class, first_page, freezed);
+out_class_unlock:
+ spin_unlock(&class->lock);
+
+ return ret;
+}
+
+void zs_page_putback(struct page *page)
+{
+ struct zs_pool *pool;
+ struct size_class *class;
+ int class_idx;
+ enum fullness_group fullness;
+ struct page *first_page;
+
+ VM_BUG_ON_PAGE(!PageMovable(page), page);
+ VM_BUG_ON_PAGE(!PageIsolated(page), page);
+
+ first_page = page;
+ get_zspage_mapping(first_page, &class_idx, &fullness);
+ pool = page->mapping->private_data;
+ class = pool->size_class[class_idx];
+
+ /*
+ * If there is race betwwen zs_free and here, free_zspage
+ * in zs_free will wait the page lock of @page without
+ * destroying of zspage.
+ */
+ INIT_LIST_HEAD(&first_page->lru);
+ spin_lock(&class->lock);
+ ClearPageIsolated(page);
+ ClearZsPageIsolate(first_page);
+ putback_zspage(class, first_page);
+ 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,
+};
+
/**
* zs_create_pool - Creates an allocation pool to work from.
* @flags: allocation flags used to allocate pool metadata
@@ -2145,6 +2409,15 @@ struct zs_pool *zs_create_pool(const cha
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.
@@ -2164,6 +2437,8 @@ void zs_destroy_pool(struct zs_pool *poo
int i;
zs_unregister_shrinker(pool);
+ if (pool->inode)
+ iput(pool->inode);
zs_pool_stat_destroy(pool);
for (i = 0; i < zs_size_classes; i++) {
@@ -2192,10 +2467,33 @@ void zs_destroy_pool(struct zs_pool *poo
}
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;
@@ -2218,6 +2516,7 @@ static int __init zs_init(void)
pr_err("zs stat initialization failed\n");
goto stat_fail;
}
+
return 0;
stat_fail:
@@ -2226,7 +2525,8 @@ stat_fail:
#endif
notifier_fail:
zs_unregister_cpu_notifier();
-
+ kern_unmount(zsmalloc_mnt);
+out:
return ret;
}
@@ -2237,6 +2537,8 @@ static void __exit zs_exit(void)
#endif
zs_unregister_cpu_notifier();
+ kern_unmount(zsmalloc_mnt);
+
zs_stat_exit();
}
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
zsmalloc-use-first_page-rather-than-page.patch
zsmalloc-clean-up-many-bug_on.patch
zsmalloc-reordering-function-parameter.patch
zsmalloc-remove-unused-pool-param-in-obj_free.patch
mm-use-put_page-to-free-page-instead-of-putback_lru_page.patch
mm-compaction-support-non-lru-movable-page-migration.patch
mm-add-non-lru-movable-page-support-document.patch
mm-balloon-use-general-movable-page-feature-into-balloon.patch
zsmalloc-keep-max_object-in-size_class.patch
zsmalloc-squeeze-inuse-into-page-mapping.patch
zsmalloc-remove-page_mapcount_reset.patch
zsmalloc-squeeze-freelist-into-page-mapping.patch
zsmalloc-move-struct-zs_meta-from-mapping-to-freelist.patch
zsmalloc-factor-page-chain-functionality-out.patch
zsmalloc-separate-free_zspage-from-putback_zspage.patch
zsmalloc-zs_compact-refactoring.patch
zsmalloc-migrate-head-page-of-zspage.patch
zsmalloc-use-single-linked-list-for-page-chain.patch
zsmalloc-migrate-tail-pages-in-zspage.patch
zram-use-__gfp_movable-for-memory-allocation.patch
--
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