Commit 41ca668a authored by Yang Shi's avatar Yang Shi Committed by Linus Torvalds
Browse files

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@gmail.com


Signed-off-by: default avatarYang Shi <shy828301@gmail.com>
Acked-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarRoman Gushchin <guro@fb.com>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 468ab843

include/linux/shrinker.h

+4 −3
Original line number Diff line number Diff line
@@ -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);

mm/vmscan.c

+15 −25
Original line number Diff line number Diff line
@@ -316,19 +316,6 @@ 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)
@@ -337,7 +324,7 @@ 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;
@@ -360,9 +347,9 @@ 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)
@@ -490,8 +477,11 @@ 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;
@@ -501,10 +491,7 @@ 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);

}
@@ -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(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;