[PATCH v3] mm: vmscan: try to reclaim swapcache pages if no swap space

[PATCH v3] mm: vmscan: try to reclaim swapcache pages if no swap space

[Liu Shixin]

When spaces of swap devices are exhausted, only file pages can be reclaimed.
But there are still some swapcache pages in anon lru list. This can lead
to a premature out-of-memory.

This problem can be fixed by checking number of swapcache pages in
can_reclaim_anon_pages().

Add a new bit swapcache_only in struct scan_control to skip isolating anon
pages that are not in the swap cache when only swap cache can be reclaimed.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
---
 include/linux/swap.h |  6 ++++++
 mm/memcontrol.c      |  8 ++++++++
 mm/vmscan.c          | 29 +++++++++++++++++++++++++++--
 3 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 456546443f1f..0318e918bfa4 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -669,6 +669,7 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_p
 }
 
 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
+extern long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg);
 extern bool mem_cgroup_swap_full(struct folio *folio);
 #else
 static inline void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
@@ -691,6 +692,11 @@ static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
 	return get_nr_swap_pages();
 }
 
+static inline long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
+{
+	return total_swapcache_pages();
+}
+
 static inline bool mem_cgroup_swap_full(struct folio *folio)
 {
 	return vm_swap_full();
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e8ca4bdcb03c..c465829db92b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7567,6 +7567,14 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
 	return nr_swap_pages;
 }
 
+long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
+{
+	if (mem_cgroup_disabled())
+		return total_swapcache_pages();
+
+	return memcg_page_state(memcg, NR_SWAPCACHE);
+}
+
 bool mem_cgroup_swap_full(struct folio *folio)
 {
 	struct mem_cgroup *memcg;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7c33c5b653ef..5cb4adf6642b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -137,6 +137,9 @@ struct scan_control {
 	/* Always discard instead of demoting to lower tier memory */
 	unsigned int no_demotion:1;
 
+	/* Swap space is exhausted, only reclaim swapcache for anon LRU */
+	unsigned int swapcache_only:1;
+
 	/* Allocation order */
 	s8 order;
 
@@ -613,10 +616,20 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
 		 */
 		if (get_nr_swap_pages() > 0)
 			return true;
+		/* Is there any swapcache pages to reclaim? */
+		if (total_swapcache_pages() > 0) {
+			sc->swapcache_only = 1;
+			return true;
+		}
 	} else {
 		/* Is the memcg below its swap limit? */
 		if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
 			return true;
+		/* Is there any swapcache pages in memcg to reclaim? */
+		if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) {
+			sc->swapcache_only = 1;
+			return true;
+		}
 	}
 
 	/*
@@ -2280,6 +2293,19 @@ static bool skip_cma(struct folio *folio, struct scan_control *sc)
 }
 #endif
 
+static bool skip_isolate(struct folio *folio, struct scan_control *sc,
+			 enum lru_list lru)
+{
+	if (folio_zonenum(folio) > sc->reclaim_idx)
+		return true;
+	if (skip_cma(folio, sc))
+		return true;
+	if (unlikely(sc->swapcache_only && !is_file_lru(lru) &&
+	    !folio_test_swapcache(folio)))
+		return true;
+	return false;
+}
+
 /*
  * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
  *
@@ -2326,8 +2352,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
 		nr_pages = folio_nr_pages(folio);
 		total_scan += nr_pages;
 
-		if (folio_zonenum(folio) > sc->reclaim_idx ||
-				skip_cma(folio, sc)) {
+		if (skip_isolate(folio, sc, lru)) {
 			nr_skipped[folio_zonenum(folio)] += nr_pages;
 			move_to = &folios_skipped;
 			goto move;
-- 
2.25.1

Re: [PATCH v3] mm: vmscan: try to reclaim swapcache pages if no swap space

[Huang, Ying]

Liu Shixin <liushixin2@huawei.com> writes:

> When spaces of swap devices are exhausted, only file pages can be reclaimed.
> But there are still some swapcache pages in anon lru list. This can lead
> to a premature out-of-memory.
>
> This problem can be fixed by checking number of swapcache pages in
> can_reclaim_anon_pages().
>
> Add a new bit swapcache_only in struct scan_control to skip isolating anon
> pages that are not in the swap cache when only swap cache can be reclaimed.

Better to describe how you test the patch and test results.

> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
> ---
>  include/linux/swap.h |  6 ++++++
>  mm/memcontrol.c      |  8 ++++++++
>  mm/vmscan.c          | 29 +++++++++++++++++++++++++++--
>  3 files changed, 41 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 456546443f1f..0318e918bfa4 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -669,6 +669,7 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_p
>  }
>  
>  extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
> +extern long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg);
>  extern bool mem_cgroup_swap_full(struct folio *folio);
>  #else
>  static inline void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
> @@ -691,6 +692,11 @@ static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>  	return get_nr_swap_pages();
>  }
>  
> +static inline long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
> +{
> +	return total_swapcache_pages();
> +}
> +
>  static inline bool mem_cgroup_swap_full(struct folio *folio)
>  {
>  	return vm_swap_full();
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e8ca4bdcb03c..c465829db92b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7567,6 +7567,14 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>  	return nr_swap_pages;
>  }
>  
> +long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
> +{
> +	if (mem_cgroup_disabled())
> +		return total_swapcache_pages();
> +
> +	return memcg_page_state(memcg, NR_SWAPCACHE);
> +}
> +
>  bool mem_cgroup_swap_full(struct folio *folio)
>  {
>  	struct mem_cgroup *memcg;
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7c33c5b653ef..5cb4adf6642b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -137,6 +137,9 @@ struct scan_control {
>  	/* Always discard instead of demoting to lower tier memory */
>  	unsigned int no_demotion:1;
>  
> +	/* Swap space is exhausted, only reclaim swapcache for anon LRU */
> +	unsigned int swapcache_only:1;
> +
>  	/* Allocation order */
>  	s8 order;
>  
> @@ -613,10 +616,20 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
>  		 */
>  		if (get_nr_swap_pages() > 0)
>  			return true;
> +		/* Is there any swapcache pages to reclaim? */
> +		if (total_swapcache_pages() > 0) {
> +			sc->swapcache_only = 1;
> +			return true;
> +		}
>  	} else {
>  		/* Is the memcg below its swap limit? */
>  		if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
>  			return true;
> +		/* Is there any swapcache pages in memcg to reclaim? */
> +		if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) {
> +			sc->swapcache_only = 1;
> +			return true;
> +		}
>  	}
>  
>  	/*
> @@ -2280,6 +2293,19 @@ static bool skip_cma(struct folio *folio, struct scan_control *sc)
>  }
>  #endif
>  
> +static bool skip_isolate(struct folio *folio, struct scan_control *sc,
> +			 enum lru_list lru)
> +{
> +	if (folio_zonenum(folio) > sc->reclaim_idx)
> +		return true;
> +	if (skip_cma(folio, sc))
> +		return true;
> +	if (unlikely(sc->swapcache_only && !is_file_lru(lru) &&
> +	    !folio_test_swapcache(folio)))

Just

	if (unlikely(sc->swapcache_only && !folio_test_swapcache(folio)))

is enough.

> +		return true;
> +	return false;
> +}
> +
>  /*
>   * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
>   *
> @@ -2326,8 +2352,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
>  		nr_pages = folio_nr_pages(folio);
>  		total_scan += nr_pages;
>  
> -		if (folio_zonenum(folio) > sc->reclaim_idx ||
> -				skip_cma(folio, sc)) {
> +		if (skip_isolate(folio, sc, lru)) {
>  			nr_skipped[folio_zonenum(folio)] += nr_pages;
>  			move_to = &folios_skipped;
>  			goto move;

--
Best Regards,
Huang, Ying

Re: [PATCH v3] mm: vmscan: try to reclaim swapcache pages if no swap space

[Liu Shixin]

On 2023/8/28 9:51, Huang, Ying wrote:
> Liu Shixin <liushixin2@huawei.com> writes:
>
>> When spaces of swap devices are exhausted, only file pages can be reclaimed.
>> But there are still some swapcache pages in anon lru list. This can lead
>> to a premature out-of-memory.
>>
>> This problem can be fixed by checking number of swapcache pages in
>> can_reclaim_anon_pages().
>>
>> Add a new bit swapcache_only in struct scan_control to skip isolating anon
>> pages that are not in the swap cache when only swap cache can be reclaimed.
> Better to describe how you test the patch and test results.
OK, I will add the infomation.
>
>> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
>> ---
>>  include/linux/swap.h |  6 ++++++
>>  mm/memcontrol.c      |  8 ++++++++
>>  mm/vmscan.c          | 29 +++++++++++++++++++++++++++--
>>  3 files changed, 41 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/swap.h b/include/linux/swap.h
>> index 456546443f1f..0318e918bfa4 100644
>> --- a/include/linux/swap.h
>> +++ b/include/linux/swap.h
>> @@ -669,6 +669,7 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_p
>>  }
>>  
>>  extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
>> +extern long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg);
>>  extern bool mem_cgroup_swap_full(struct folio *folio);
>>  #else
>>  static inline void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
>> @@ -691,6 +692,11 @@ static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>>  	return get_nr_swap_pages();
>>  }
>>  
>> +static inline long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
>> +{
>> +	return total_swapcache_pages();
>> +}
>> +
>>  static inline bool mem_cgroup_swap_full(struct folio *folio)
>>  {
>>  	return vm_swap_full();
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index e8ca4bdcb03c..c465829db92b 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -7567,6 +7567,14 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>>  	return nr_swap_pages;
>>  }
>>  
>> +long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
>> +{
>> +	if (mem_cgroup_disabled())
>> +		return total_swapcache_pages();
>> +
>> +	return memcg_page_state(memcg, NR_SWAPCACHE);
>> +}
>> +
>>  bool mem_cgroup_swap_full(struct folio *folio)
>>  {
>>  	struct mem_cgroup *memcg;
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 7c33c5b653ef..5cb4adf6642b 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -137,6 +137,9 @@ struct scan_control {
>>  	/* Always discard instead of demoting to lower tier memory */
>>  	unsigned int no_demotion:1;
>>  
>> +	/* Swap space is exhausted, only reclaim swapcache for anon LRU */
>> +	unsigned int swapcache_only:1;
>> +
>>  	/* Allocation order */
>>  	s8 order;
>>  
>> @@ -613,10 +616,20 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
>>  		 */
>>  		if (get_nr_swap_pages() > 0)
>>  			return true;
>> +		/* Is there any swapcache pages to reclaim? */
>> +		if (total_swapcache_pages() > 0) {
>> +			sc->swapcache_only = 1;
>> +			return true;
>> +		}
>>  	} else {
>>  		/* Is the memcg below its swap limit? */
>>  		if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
>>  			return true;
>> +		/* Is there any swapcache pages in memcg to reclaim? */
>> +		if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) {
>> +			sc->swapcache_only = 1;
>> +			return true;
>> +		}
>>  	}
>>  
>>  	/*
>> @@ -2280,6 +2293,19 @@ static bool skip_cma(struct folio *folio, struct scan_control *sc)
>>  }
>>  #endif
>>  
>> +static bool skip_isolate(struct folio *folio, struct scan_control *sc,
>> +			 enum lru_list lru)
>> +{
>> +	if (folio_zonenum(folio) > sc->reclaim_idx)
>> +		return true;
>> +	if (skip_cma(folio, sc))
>> +		return true;
>> +	if (unlikely(sc->swapcache_only && !is_file_lru(lru) &&
>> +	    !folio_test_swapcache(folio)))
> Just
>
> 	if (unlikely(sc->swapcache_only && !folio_test_swapcache(folio)))
>
> is enough.
That would results the file pages to be skipped too, but what expected is to skip non-swapcache
pages in anon lru list. So I think the condition !is_file_lru(lru) is required.

Thanks,
>
>> +		return true;
>> +	return false;
>> +}
>> +
>>  /*
>>   * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
>>   *
>> @@ -2326,8 +2352,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
>>  		nr_pages = folio_nr_pages(folio);
>>  		total_scan += nr_pages;
>>  
>> -		if (folio_zonenum(folio) > sc->reclaim_idx ||
>> -				skip_cma(folio, sc)) {
>> +		if (skip_isolate(folio, sc, lru)) {
>>  			nr_skipped[folio_zonenum(folio)] += nr_pages;
>>  			move_to = &folios_skipped;
>>  			goto move;
> --
> Best Regards,
> Huang, Ying
> .
>

Re: [PATCH v3] mm: vmscan: try to reclaim swapcache pages if no swap space

[Huang, Ying]

Liu Shixin <liushixin2@huawei.com> writes:

> On 2023/8/28 9:51, Huang, Ying wrote:
>> Liu Shixin <liushixin2@huawei.com> writes:
>>
>>> When spaces of swap devices are exhausted, only file pages can be reclaimed.
>>> But there are still some swapcache pages in anon lru list. This can lead
>>> to a premature out-of-memory.
>>>
>>> This problem can be fixed by checking number of swapcache pages in
>>> can_reclaim_anon_pages().
>>>
>>> Add a new bit swapcache_only in struct scan_control to skip isolating anon
>>> pages that are not in the swap cache when only swap cache can be reclaimed.
>> Better to describe how you test the patch and test results.
> OK, I will add the infomation.
>>
>>> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
>>> ---
>>>  include/linux/swap.h |  6 ++++++
>>>  mm/memcontrol.c      |  8 ++++++++
>>>  mm/vmscan.c          | 29 +++++++++++++++++++++++++++--
>>>  3 files changed, 41 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/include/linux/swap.h b/include/linux/swap.h
>>> index 456546443f1f..0318e918bfa4 100644
>>> --- a/include/linux/swap.h
>>> +++ b/include/linux/swap.h
>>> @@ -669,6 +669,7 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_p
>>>  }
>>>  
>>>  extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
>>> +extern long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg);
>>>  extern bool mem_cgroup_swap_full(struct folio *folio);
>>>  #else
>>>  static inline void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
>>> @@ -691,6 +692,11 @@ static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>>>  	return get_nr_swap_pages();
>>>  }
>>>  
>>> +static inline long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
>>> +{
>>> +	return total_swapcache_pages();
>>> +}
>>> +
>>>  static inline bool mem_cgroup_swap_full(struct folio *folio)
>>>  {
>>>  	return vm_swap_full();
>>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>>> index e8ca4bdcb03c..c465829db92b 100644
>>> --- a/mm/memcontrol.c
>>> +++ b/mm/memcontrol.c
>>> @@ -7567,6 +7567,14 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>>>  	return nr_swap_pages;
>>>  }
>>>  
>>> +long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
>>> +{
>>> +	if (mem_cgroup_disabled())
>>> +		return total_swapcache_pages();
>>> +
>>> +	return memcg_page_state(memcg, NR_SWAPCACHE);
>>> +}
>>> +
>>>  bool mem_cgroup_swap_full(struct folio *folio)
>>>  {
>>>  	struct mem_cgroup *memcg;
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index 7c33c5b653ef..5cb4adf6642b 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -137,6 +137,9 @@ struct scan_control {
>>>  	/* Always discard instead of demoting to lower tier memory */
>>>  	unsigned int no_demotion:1;
>>>  
>>> +	/* Swap space is exhausted, only reclaim swapcache for anon LRU */
>>> +	unsigned int swapcache_only:1;
>>> +
>>>  	/* Allocation order */
>>>  	s8 order;
>>>  
>>> @@ -613,10 +616,20 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
>>>  		 */
>>>  		if (get_nr_swap_pages() > 0)
>>>  			return true;
>>> +		/* Is there any swapcache pages to reclaim? */
>>> +		if (total_swapcache_pages() > 0) {
>>> +			sc->swapcache_only = 1;
>>> +			return true;
>>> +		}
>>>  	} else {
>>>  		/* Is the memcg below its swap limit? */
>>>  		if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
>>>  			return true;
>>> +		/* Is there any swapcache pages in memcg to reclaim? */
>>> +		if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) {
>>> +			sc->swapcache_only = 1;
>>> +			return true;
>>> +		}
>>>  	}
>>>  
>>>  	/*
>>> @@ -2280,6 +2293,19 @@ static bool skip_cma(struct folio *folio, struct scan_control *sc)
>>>  }
>>>  #endif
>>>  
>>> +static bool skip_isolate(struct folio *folio, struct scan_control *sc,
>>> +			 enum lru_list lru)
>>> +{
>>> +	if (folio_zonenum(folio) > sc->reclaim_idx)
>>> +		return true;
>>> +	if (skip_cma(folio, sc))
>>> +		return true;
>>> +	if (unlikely(sc->swapcache_only && !is_file_lru(lru) &&
>>> +	    !folio_test_swapcache(folio)))
>> Just
>>
>> 	if (unlikely(sc->swapcache_only && !folio_test_swapcache(folio)))
>>
>> is enough.
> That would results the file pages to be skipped too, but what expected is to skip non-swapcache
> pages in anon lru list. So I think the condition !is_file_lru(lru) is required.

Ah, you are right.

--
Best Regards,
Huang, Ying

>>
>>> +		return true;
>>> +	return false;
>>> +}
>>> +
>>>  /*
>>>   * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
>>>   *
>>> @@ -2326,8 +2352,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
>>>  		nr_pages = folio_nr_pages(folio);
>>>  		total_scan += nr_pages;
>>>  
>>> -		if (folio_zonenum(folio) > sc->reclaim_idx ||
>>> -				skip_cma(folio, sc)) {
>>> +		if (skip_isolate(folio, sc, lru)) {
>>>  			nr_skipped[folio_zonenum(folio)] += nr_pages;
>>>  			move_to = &folios_skipped;
>>>  			goto move;

Re: [PATCH v3] mm: vmscan: try to reclaim swapcache pages if no swap space

[Yosry Ahmed]

On Fri, Aug 25, 2023 at 7:49 PM Liu Shixin <liushixin2@huawei.com> wrote:
>
> When spaces of swap devices are exhausted, only file pages can be reclaimed.
> But there are still some swapcache pages in anon lru list. This can lead
> to a premature out-of-memory.
>
> This problem can be fixed by checking number of swapcache pages in
> can_reclaim_anon_pages().
>
> Add a new bit swapcache_only in struct scan_control to skip isolating anon
> pages that are not in the swap cache when only swap cache can be reclaimed.
>
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>

I can confirm that with the reproducer I posted on v2 this patch fixes
the problem, feel free to add:

Tested-by: Yosry Ahmed <yosryahmed@google.com>

The code LGTM. I personally prefer that we add NR_SWAPCACHE to
memcg1_stats, so that it's obvious that it is used by cgroup v1 code,
but perhaps maintainers have opinions against that.

> ---
>  include/linux/swap.h |  6 ++++++
>  mm/memcontrol.c      |  8 ++++++++
>  mm/vmscan.c          | 29 +++++++++++++++++++++++++++--
>  3 files changed, 41 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 456546443f1f..0318e918bfa4 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -669,6 +669,7 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_p
>  }
>
>  extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
> +extern long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg);
>  extern bool mem_cgroup_swap_full(struct folio *folio);
>  #else
>  static inline void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
> @@ -691,6 +692,11 @@ static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>         return get_nr_swap_pages();
>  }
>
> +static inline long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
> +{
> +       return total_swapcache_pages();
> +}
> +
>  static inline bool mem_cgroup_swap_full(struct folio *folio)
>  {
>         return vm_swap_full();
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e8ca4bdcb03c..c465829db92b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7567,6 +7567,14 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>         return nr_swap_pages;
>  }
>
> +long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg)
> +{
> +       if (mem_cgroup_disabled())
> +               return total_swapcache_pages();
> +
> +       return memcg_page_state(memcg, NR_SWAPCACHE);
> +}
> +
>  bool mem_cgroup_swap_full(struct folio *folio)
>  {
>         struct mem_cgroup *memcg;
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7c33c5b653ef..5cb4adf6642b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -137,6 +137,9 @@ struct scan_control {
>         /* Always discard instead of demoting to lower tier memory */
>         unsigned int no_demotion:1;
>
> +       /* Swap space is exhausted, only reclaim swapcache for anon LRU */
> +       unsigned int swapcache_only:1;
> +
>         /* Allocation order */
>         s8 order;
>
> @@ -613,10 +616,20 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
>                  */
>                 if (get_nr_swap_pages() > 0)
>                         return true;
> +               /* Is there any swapcache pages to reclaim? */
> +               if (total_swapcache_pages() > 0) {
> +                       sc->swapcache_only = 1;
> +                       return true;
> +               }
>         } else {
>                 /* Is the memcg below its swap limit? */
>                 if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
>                         return true;
> +               /* Is there any swapcache pages in memcg to reclaim? */
> +               if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) {
> +                       sc->swapcache_only = 1;
> +                       return true;
> +               }
>         }
>
>         /*
> @@ -2280,6 +2293,19 @@ static bool skip_cma(struct folio *folio, struct scan_control *sc)
>  }
>  #endif
>
> +static bool skip_isolate(struct folio *folio, struct scan_control *sc,
> +                        enum lru_list lru)
> +{
> +       if (folio_zonenum(folio) > sc->reclaim_idx)
> +               return true;
> +       if (skip_cma(folio, sc))
> +               return true;
> +       if (unlikely(sc->swapcache_only && !is_file_lru(lru) &&
> +           !folio_test_swapcache(folio)))
> +               return true;
> +       return false;
> +}
> +
>  /*
>   * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
>   *
> @@ -2326,8 +2352,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
>                 nr_pages = folio_nr_pages(folio);
>                 total_scan += nr_pages;
>
> -               if (folio_zonenum(folio) > sc->reclaim_idx ||
> -                               skip_cma(folio, sc)) {
> +               if (skip_isolate(folio, sc, lru)) {
>                         nr_skipped[folio_zonenum(folio)] += nr_pages;
>                         move_to = &folios_skipped;
>                         goto move;
> --
> 2.25.1
>