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 <ktk...@virtuozzo.com>
Acked-by: Vlastimil Babka <vba...@suse.cz>
Acked-by: Roman Gushchin <g...@fb.com>
Reviewed-by: Shakeel Butt <shake...@google.com>
Signed-off-by: Yang Shi <shy828...@gmail.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 c0d04f242917..d0876970601e 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)
@@ -488,8 +475,11 @@ 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;
@@ -499,10 +489,7 @@ 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);
}
@@ -522,13 +509,16 @@ 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;
}
@@ -693,7 +683,7 @@ 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
