diff mbox series

[v8,08/13] mm: vmscan: use a new flag to indicate shrinker is registered

Message ID 20210217001322.2226796-9-shy828301@gmail.com (mailing list archive)
State New, archived
Headers show
Series Make shrinker's nr_deferred memcg aware | expand

Commit Message

Yang Shi Feb. 17, 2021, 12:13 a.m. UTC 
Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred.
This approach is fine with nr_deferred at the shrinker level, but the following
patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their
shrinker->nr_deferred would always be NULL.  This would prevent the shrinkers
from unregistering correctly.

Remove SHRINKER_REGISTERING since we could check if shrinker is registered
successfully by the new flag.

Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Yang Shi <shy828301@gmail.com>
---
 include/linux/shrinker.h |  7 ++++---
 mm/vmscan.c              | 40 +++++++++++++++-------------------------
 2 files changed, 19 insertions(+), 28 deletions(-)

Comments

Roman Gushchin Feb. 17, 2021, 2 a.m. UTC | #1 
On Tue, Feb 16, 2021 at 04:13:17PM -0800, Yang Shi wrote:
> Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred.
> This approach is fine with nr_deferred at the shrinker level, but the following
> patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their
> shrinker->nr_deferred would always be NULL.  This would prevent the shrinkers
> from unregistering correctly.
> 
> Remove SHRINKER_REGISTERING since we could check if shrinker is registered
> successfully by the new flag.
> 
> Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Yang Shi <shy828301@gmail.com>

Acked-by: Roman Gushchin <guro@fb.com>

> ---
>  include/linux/shrinker.h |  7 ++++---
>  mm/vmscan.c              | 40 +++++++++++++++-------------------------
>  2 files changed, 19 insertions(+), 28 deletions(-)
> 
> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index 0f80123650e2..1eac79ce57d4 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -79,13 +79,14 @@ struct shrinker {
>  #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
>  
>  /* Flags */
> -#define SHRINKER_NUMA_AWARE	(1 << 0)
> -#define SHRINKER_MEMCG_AWARE	(1 << 1)
> +#define SHRINKER_REGISTERED	(1 << 0)
> +#define SHRINKER_NUMA_AWARE	(1 << 1)
> +#define SHRINKER_MEMCG_AWARE	(1 << 2)
>  /*
>   * It just makes sense when the shrinker is also MEMCG_AWARE for now,
>   * non-MEMCG_AWARE shrinker should not have this flag set.
>   */
> -#define SHRINKER_NONSLAB	(1 << 2)
> +#define SHRINKER_NONSLAB	(1 << 3)
>  
>  extern int prealloc_shrinker(struct shrinker *shrinker);
>  extern void register_shrinker_prepared(struct shrinker *shrinker);
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index fe6e25f46b55..a1047ea60ecf 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -314,19 +314,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
>  	}
>  }
>  
> -/*
> - * We allow subsystems to populate their shrinker-related
> - * LRU lists before register_shrinker_prepared() is called
> - * for the shrinker, since we don't want to impose
> - * restrictions on their internal registration order.
> - * In this case shrink_slab_memcg() may find corresponding
> - * bit is set in the shrinkers map.
> - *
> - * This value is used by the function to detect registering
> - * shrinkers and to skip do_shrink_slab() calls for them.
> - */
> -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
> -
>  static DEFINE_IDR(shrinker_idr);
>  
>  static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> @@ -335,7 +322,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
>  
>  	down_write(&shrinker_rwsem);
>  	/* This may call shrinker, so it must use down_read_trylock() */
> -	id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
> +	id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
>  	if (id < 0)
>  		goto unlock;
>  
> @@ -358,9 +345,9 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
>  
>  	BUG_ON(id < 0);
>  
> -	down_write(&shrinker_rwsem);
> +	lockdep_assert_held(&shrinker_rwsem);
> +
>  	idr_remove(&shrinker_idr, id);
> -	up_write(&shrinker_rwsem);
>  }
>  
>  static bool cgroup_reclaim(struct scan_control *sc)
> @@ -487,8 +474,11 @@ void free_prealloced_shrinker(struct shrinker *shrinker)
>  	if (!shrinker->nr_deferred)
>  		return;
>  
> -	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> +	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> +		down_write(&shrinker_rwsem);
>  		unregister_memcg_shrinker(shrinker);
> +		up_write(&shrinker_rwsem);
> +	}
>  
>  	kfree(shrinker->nr_deferred);
>  	shrinker->nr_deferred = NULL;
> @@ -498,10 +488,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
>  {
>  	down_write(&shrinker_rwsem);
>  	list_add_tail(&shrinker->list, &shrinker_list);
> -#ifdef CONFIG_MEMCG
> -	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> -		idr_replace(&shrinker_idr, shrinker, shrinker->id);
> -#endif
> +	shrinker->flags |= SHRINKER_REGISTERED;
>  	up_write(&shrinker_rwsem);
>  }
>  
> @@ -521,13 +508,16 @@ EXPORT_SYMBOL(register_shrinker);
>   */
>  void unregister_shrinker(struct shrinker *shrinker)
>  {
> -	if (!shrinker->nr_deferred)
> +	if (!(shrinker->flags & SHRINKER_REGISTERED))
>  		return;
> -	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> -		unregister_memcg_shrinker(shrinker);
> +
>  	down_write(&shrinker_rwsem);
>  	list_del(&shrinker->list);
> +	shrinker->flags &= ~SHRINKER_REGISTERED;
> +	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> +		unregister_memcg_shrinker(shrinker);
>  	up_write(&shrinker_rwsem);
> +
>  	kfree(shrinker->nr_deferred);
>  	shrinker->nr_deferred = NULL;
>  }
> @@ -692,7 +682,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
>  		struct shrinker *shrinker;
>  
>  		shrinker = idr_find(&shrinker_idr, i);
> -		if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) {
> +		if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) {
>  			if (!shrinker)
>  				clear_bit(i, info->map);
>  			continue;
> -- 
> 2.26.2
>
Shakeel Butt March 8, 2021, 5:48 p.m. UTC | #2 
On Tue, Feb 16, 2021 at 4:13 PM Yang Shi <shy828301@gmail.com> wrote:
>
> Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred.
> This approach is fine with nr_deferred at the shrinker level, but the following
> patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their
> shrinker->nr_deferred would always be NULL.  This would prevent the shrinkers
> from unregistering correctly.
>
> Remove SHRINKER_REGISTERING since we could check if shrinker is registered
> successfully by the new flag.
>
> Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Yang Shi <shy828301@gmail.com>

Reviewed-by: Shakeel Butt <shakeelb@google.com>
diff mbox series

Patch

diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 0f80123650e2..1eac79ce57d4 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -79,13 +79,14 @@  struct shrinker {
 #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
 
 /* Flags */
-#define SHRINKER_NUMA_AWARE	(1 << 0)
-#define SHRINKER_MEMCG_AWARE	(1 << 1)
+#define SHRINKER_REGISTERED	(1 << 0)
+#define SHRINKER_NUMA_AWARE	(1 << 1)
+#define SHRINKER_MEMCG_AWARE	(1 << 2)
 /*
  * It just makes sense when the shrinker is also MEMCG_AWARE for now,
  * non-MEMCG_AWARE shrinker should not have this flag set.
  */
-#define SHRINKER_NONSLAB	(1 << 2)
+#define SHRINKER_NONSLAB	(1 << 3)
 
 extern int prealloc_shrinker(struct shrinker *shrinker);
 extern void register_shrinker_prepared(struct shrinker *shrinker);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index fe6e25f46b55..a1047ea60ecf 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -314,19 +314,6 @@  void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
 	}
 }
 
-/*
- * We allow subsystems to populate their shrinker-related
- * LRU lists before register_shrinker_prepared() is called
- * for the shrinker, since we don't want to impose
- * restrictions on their internal registration order.
- * In this case shrink_slab_memcg() may find corresponding
- * bit is set in the shrinkers map.
- *
- * This value is used by the function to detect registering
- * shrinkers and to skip do_shrink_slab() calls for them.
- */
-#define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
-
 static DEFINE_IDR(shrinker_idr);
 
 static int prealloc_memcg_shrinker(struct shrinker *shrinker)
@@ -335,7 +322,7 @@  static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 
 	down_write(&shrinker_rwsem);
 	/* This may call shrinker, so it must use down_read_trylock() */
-	id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
+	id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
 	if (id < 0)
 		goto unlock;
 
@@ -358,9 +345,9 @@  static void unregister_memcg_shrinker(struct shrinker *shrinker)
 
 	BUG_ON(id < 0);
 
-	down_write(&shrinker_rwsem);
+	lockdep_assert_held(&shrinker_rwsem);
+
 	idr_remove(&shrinker_idr, id);
-	up_write(&shrinker_rwsem);
 }
 
 static bool cgroup_reclaim(struct scan_control *sc)
@@ -487,8 +474,11 @@  void free_prealloced_shrinker(struct shrinker *shrinker)
 	if (!shrinker->nr_deferred)
 		return;
 
-	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
+		down_write(&shrinker_rwsem);
 		unregister_memcg_shrinker(shrinker);
+		up_write(&shrinker_rwsem);
+	}
 
 	kfree(shrinker->nr_deferred);
 	shrinker->nr_deferred = NULL;
@@ -498,10 +488,7 @@  void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG
-	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
-		idr_replace(&shrinker_idr, shrinker, shrinker->id);
-#endif
+	shrinker->flags |= SHRINKER_REGISTERED;
 	up_write(&shrinker_rwsem);
 }
 
@@ -521,13 +508,16 @@  EXPORT_SYMBOL(register_shrinker);
  */
 void unregister_shrinker(struct shrinker *shrinker)
 {
-	if (!shrinker->nr_deferred)
+	if (!(shrinker->flags & SHRINKER_REGISTERED))
 		return;
-	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
-		unregister_memcg_shrinker(shrinker);
+
 	down_write(&shrinker_rwsem);
 	list_del(&shrinker->list);
+	shrinker->flags &= ~SHRINKER_REGISTERED;
+	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+		unregister_memcg_shrinker(shrinker);
 	up_write(&shrinker_rwsem);
+
 	kfree(shrinker->nr_deferred);
 	shrinker->nr_deferred = NULL;
 }
@@ -692,7 +682,7 @@  static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
 		struct shrinker *shrinker;
 
 		shrinker = idr_find(&shrinker_idr, i);
-		if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) {
+		if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) {
 			if (!shrinker)
 				clear_bit(i, info->map);
 			continue;