Hi Hui,
On Mon, Aug 14, 2017 at 05:56:30PM +0800, Hui Zhu wrote:
> After commit e2846124f9a2 ("zsmalloc: zs_page_migrate: skip unnecessary
This patch is not merged yet so the hash is invalid.
That means we may fold this patch to [1] in current mmotm.
[1]
zsmalloc-zs_page_migrate-skip-unnecessary-loops-but-not-return-ebusy-if-zspage-is-not-inuse-fix.patch
> loops but not return -EBUSY if zspage is not inuse") 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;
> }
I also realized we should make zs_page_isolate succeed on empty zspage
because we allow the empty zspage migration from now on.
Could you send a patch for that as well?
> The page of this zspage was migrated in before.
>
> The reason is commit e2846124f9a2 ("zsmalloc: zs_page_migrate: skip
> unnecessary loops but not return -EBUSY if zspage is not inuse") 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.
>
> Fixes: e2846124f9a2 ("zsmalloc: zs_page_migrate: skip unnecessary loops but
> not return -EBUSY if zspage is not inuse")
> Signed-off-by: Hui Zhu <[email protected]>
> ---
> mm/zsmalloc.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 62457eb..c6cc77c 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -2035,8 +2035,17 @@ 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)) {
> + /*
> + * Page will be freed in following part. But newpage and
> + * zspage will stay in system if zspage is in ZS_EMPTY
> + * list. So call free_work to free it.
> + * The page and class is locked, we cannot free zspage
> + * immediately so let's defer.
> + */
How about this?
/*
* 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
>
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