[PATCH v2] zsmalloc: zs_page_migrate: schedule free_work if zspage is ZS_EMPTY

[PATCH v2] zsmalloc: zs_page_migrate: schedule free_work if zspage is ZS_EMPTY

[Hui Zhu]

After commit e2846124f9a2 ("zsmalloc: zs_page_migrate: skip unnecessary
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;
	}
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 <zhuhui@xiaomi.com>
---
 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.
+		 */
+		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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Re: [PATCH v2] zsmalloc: zs_page_migrate: schedule free_work if zspage is ZS_EMPTY

[Minchan Kim]

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 <zhuhui@xiaomi.com>
> ---
>  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
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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Re: [PATCH v2] zsmalloc: zs_page_migrate: schedule free_work if zspage is ZS_EMPTY

[Hui Zhu]

Hi Minchan,

2017-08-16 10:13 GMT+08:00 Minchan Kim <minchan@kernel.org>:
> 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?

OK.  I will make a patch for that later.

Thanks,
Hui

>
>> 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 <zhuhui@xiaomi.com>
>> ---
>>  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
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@kvack.org.  For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
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Re: [PATCH v2] zsmalloc: zs_page_migrate: schedule free_work if zspage is ZS_EMPTY

[Minchan Kim]

On Wed, Aug 16, 2017 at 10:49:14AM +0800, Hui Zhu wrote:
> Hi Minchan,
> 
> 2017-08-16 10:13 GMT+08:00 Minchan Kim <minchan@kernel.org>:
> > 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?
> 
> OK.  I will make a patch for that later.

Please send the patch so I want to fold it to [1] before Andrew is going
to send [1] to Linus.

Thanks.

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Re: [PATCH v2] zsmalloc: zs_page_migrate: schedule free_work if zspage is ZS_EMPTY

[Hui Zhu]

2017-08-16 12:51 GMT+08:00 Minchan Kim <minchan@kernel.org>:
> On Wed, Aug 16, 2017 at 10:49:14AM +0800, Hui Zhu wrote:
>> Hi Minchan,
>>
>> 2017-08-16 10:13 GMT+08:00 Minchan Kim <minchan@kernel.org>:
>> > 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?
>>
>> OK.  I will make a patch for that later.
>
> Please send the patch so I want to fold it to [1] before Andrew is going
> to send [1] to Linus.
>
> Thanks.

Done.

Thanks,
Hui

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