The patch titled
Subject: mm: vmscan: use a new flag to indicate shrinker is registered
has been added to the -mm tree. Its filename is
mm-vmscan-use-a-new-flag-to-indicate-shrinker-is-registered.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-vmscan-use-a-new-flag-to-indicate-shrinker-is-registered.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-use-a-new-flag-to-indicate-shrinker-is-registered.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
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------------------------------------------------------
From: Yang Shi <shy828301@xxxxxxxxx>
Subject: mm: vmscan: use a new flag to indicate shrinker is registered
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@xxxxxxxxx
Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
Acked-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/shrinker.h | 7 +++---
mm/vmscan.c | 40 +++++++++++++------------------------
2 files changed, 19 insertions(+), 28 deletions(-)
--- a/include/linux/shrinker.h~mm-vmscan-use-a-new-flag-to-indicate-shrinker-is-registered
+++ a/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);
--- a/mm/vmscan.c~mm-vmscan-use-a-new-flag-to-indicate-shrinker-is-registered
+++ a/mm/vmscan.c
@@ -316,19 +316,6 @@ void set_shrinker_bit(struct mem_cgroup
}
}
-/*
- * 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)
@@ -337,7 +324,7 @@ static int prealloc_memcg_shrinker(struc
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;
@@ -360,9 +347,9 @@ static void unregister_memcg_shrinker(st
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)
@@ -490,8 +477,11 @@ void free_prealloced_shrinker(struct shr
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;
@@ -501,10 +491,7 @@ void register_shrinker_prepared(struct s
{
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);
}
@@ -524,13 +511,16 @@ 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;
}
@@ -695,7 +685,7 @@ static unsigned long shrink_slab_memcg(g
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;
_
Patches currently in -mm which might be from shy828301@xxxxxxxxx are
mm-vmscan-use-nid-from-shrink_control-for-tracepoint.patch
mm-vmscan-consolidate-shrinker_maps-handling-code.patch
mm-vmscan-use-shrinker_rwsem-to-protect-shrinker_maps-allocation.patch
mm-vmscan-remove-memcg_shrinker_map_size.patch
mm-vmscan-use-kvfree_rcu-instead-of-call_rcu.patch
mm-memcontrol-rename-shrinker_map-to-shrinker_info.patch
mm-vmscan-add-shrinker_info_protected-helper.patch
mm-vmscan-use-a-new-flag-to-indicate-shrinker-is-registered.patch
mm-vmscan-add-per-memcg-shrinker-nr_deferred.patch
mm-vmscan-use-per-memcg-nr_deferred-of-shrinker.patch
mm-vmscan-dont-need-allocate-shrinker-nr_deferred-for-memcg-aware-shrinkers.patch
mm-memcontrol-reparent-nr_deferred-when-memcg-offline.patch
mm-vmscan-shrink-deferred-objects-proportional-to-priority.patch
