2017-08-16 03:20:16

by Hui Zhu

Subject: [PATCH v3] zsmalloc: zs_page_migrate: schedule free_work if zspage is ZS_EMPTY

After commit [1] zs_page_migrate can handle the ZS_EMPTY zspage.

But I got some false in zs_page_isolate:
if (get_zspage_inuse(zspage) == 0) {
spin_unlock(&class->lock);
return false;
}
The page of this zspage was migrated in before.

The reason is commit [1] just handle the "page" but not "newpage"
then it keep the "newpage" with a empty zspage inside system.
Root cause is zs_page_isolate remove it from ZS_EMPTY list but not
call zs_page_putback "schedule_work(&pool->free_work);". Because
zs_page_migrate done the job without "schedule_work(&pool->free_work);"

Make this patch let zs_page_migrate wake up free_work if need.

[1] zsmalloc-zs_page_migrate-skip-unnecessary-loops-but-not-return-ebusy-if-zspage-is-not-inuse-fix.patch

Signed-off-by: Hui Zhu <[email protected]>
---
mm/zsmalloc.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 62457eb..fb99953 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -2035,8 +2035,15 @@ int zs_page_migrate(struct address_space *mapping, struct page *newpage,
* 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))
- putback_zspage(class, zspage);
+ if (!is_zspage_isolated(zspage)) {
+ /*
+ * Since we allow empty zspage migration, putback of zspage
+ * should free empty zspage. Otherwise, it could make a leak
+ * until upcoming free_work is done, which isn't guaranteed.
+ */
+ if (putback_zspage(class, zspage) == ZS_EMPTY)
+ schedule_work(&pool->free_work);
+ }

reset_page(page);
put_page(page);
--
1.9.1

2017-08-16 04:01:10

by Minchan Kim

Subject: Re: [PATCH v3] zsmalloc: zs_page_migrate: schedule free_work if zspage is ZS_EMPTY

On Wed, Aug 16, 2017 at 11:19:41AM +0800, Hui Zhu wrote:
> After commit [1] zs_page_migrate can handle the ZS_EMPTY zspage.
>
> But I got some false in zs_page_isolate:
> if (get_zspage_inuse(zspage) == 0) {
> spin_unlock(&class->lock);
> return false;
> }
> The page of this zspage was migrated in before.
>
> The reason is commit [1] just handle the "page" but not "newpage"
> then it keep the "newpage" with a empty zspage inside system.
> Root cause is zs_page_isolate remove it from ZS_EMPTY list but not
> call zs_page_putback "schedule_work(&pool->free_work);". Because
> zs_page_migrate done the job without "schedule_work(&pool->free_work);"
>
> Make this patch let zs_page_migrate wake up free_work if need.
>
> [1] zsmalloc-zs_page_migrate-skip-unnecessary-loops-but-not-return-ebusy-if-zspage-is-not-inuse-fix.patch
>
> Signed-off-by: Hui Zhu <[email protected]>
Acked-by: Minchan Kim <[email protected]>

Thanks!