From: Yang Shi
mainline inclusion
from mainline-5.13-rc1
commit 41ca668a71e7b03743369a2c6d8b8edc1e943dc8
category: bugfix
issue: #I3ZXZF
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
---------------------------
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.
Link: https://lkml.kernel.org/r/20210311190845.9708-9-shy828301@gmail.com
Signed-off-by: Yang Shi
Acked-by: Kirill Tkhai
Acked-by: Vlastimil Babka
Acked-by: Roman Gushchin
Reviewed-by: Shakeel Butt
Cc: Dave Chinner
Cc: Johannes Weiner
Cc: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
Conflict:
mm/vmscan.c
Signed-off-by: Zhang Yi
Reviewed-by: Yang Erkun
Signed-off-by: Chen Jun
Signed-off-by: Yu Changchun
---
include/linux/shrinker.h | 7 ++++---
mm/vmscan.c | 39 +++++++++++++++------------------------
2 files changed, 19 insertions(+), 27 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 67d38334052e..3c6aa8b9caa9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -187,18 +187,6 @@ static LIST_HEAD(shrinker_list);
static DECLARE_RWSEM(shrinker_rwsem);
#ifdef CONFIG_MEMCG
-/*
- * 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 shrinker_nr_max;
@@ -209,7 +197,7 @@ 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;
@@ -234,9 +222,9 @@ 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)
@@ -363,8 +351,11 @@ 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;
@@ -374,10 +365,7 @@ 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);
}
@@ -397,13 +385,16 @@ 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;
}
@@ -569,7 +560,7 @@ 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, map->map);
continue;
--
2.22.0
