Commit 07222371 authored by Shakeel Butt's avatar Shakeel Butt Committed by Andrew Morton
Browse files

memcg: replace memcg ID idr with xarray 

At the moment memcg IDs are managed through IDR which requires external
synchronization mechanisms and makes the allocation code a bit awkward. 
Let's switch to xarray and make the code simpler.

[shakeel.butt@linux.dev: fix error path in mem_cgroup_alloc(), per Dan]
  Link: https://lkml.kernel.org/r/20240815155402.3630804-1-shakeel.butt@linux.dev
Link: https://lkml.kernel.org/r/20240809172618.2946790-1-shakeel.butt@linux.dev


Signed-off-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Suggested-by: default avatarMatthew Wilcox <willy@infradead.org>
Reviewed-by: default avatarRoman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarMuchun Song <muchun.song@linux.dev>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 072cd213

mm/memcontrol.c

+10 −29
Original line number Diff line number Diff line
@@ -3363,29 +3363,12 @@ static void memcg_wb_domain_size_changed(struct mem_cgroup *memcg) 
 */



#define MEM_CGROUP_ID_MAX	((1UL << MEM_CGROUP_ID_SHIFT) - 1)

static DEFINE_IDR(mem_cgroup_idr);

static DEFINE_SPINLOCK(memcg_idr_lock);



static int mem_cgroup_alloc_id(void)

{

	int ret;



	idr_preload(GFP_KERNEL);

	spin_lock(&memcg_idr_lock);

	ret = idr_alloc(&mem_cgroup_idr, NULL, 1, MEM_CGROUP_ID_MAX + 1,

			GFP_NOWAIT);

	spin_unlock(&memcg_idr_lock);

	idr_preload_end();

	return ret;

}

static DEFINE_XARRAY_ALLOC1(mem_cgroup_ids);



static void mem_cgroup_id_remove(struct mem_cgroup *memcg)

{

	if (memcg->id.id > 0) {

		spin_lock(&memcg_idr_lock);

		idr_remove(&mem_cgroup_idr, memcg->id.id);

		spin_unlock(&memcg_idr_lock);



		xa_erase(&mem_cgroup_ids, memcg->id.id);

		memcg->id.id = 0;

	}

}
@@ -3420,7 +3403,7 @@ static inline void mem_cgroup_id_put(struct mem_cgroup *memcg) 
struct mem_cgroup *mem_cgroup_from_id(unsigned short id)

{

	WARN_ON_ONCE(!rcu_read_lock_held());

	return idr_find(&mem_cgroup_idr, id);

	return xa_load(&mem_cgroup_ids, id);

}



#ifdef CONFIG_SHRINKER_DEBUG
@@ -3513,17 +3496,17 @@ static struct mem_cgroup *mem_cgroup_alloc(struct mem_cgroup *parent) 
	struct mem_cgroup *memcg;

	int node, cpu;

	int __maybe_unused i;

	long error = -ENOMEM;

	long error;



	memcg = kzalloc(struct_size(memcg, nodeinfo, nr_node_ids), GFP_KERNEL);

	if (!memcg)

		return ERR_PTR(error);

		return ERR_PTR(-ENOMEM);



	memcg->id.id = mem_cgroup_alloc_id();

	if (memcg->id.id < 0) {

		error = memcg->id.id;

	error = xa_alloc(&mem_cgroup_ids, &memcg->id.id, NULL,

			 XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL);

	if (error)

		goto fail;

	}

	error = -ENOMEM;



	memcg->vmstats = kzalloc(sizeof(struct memcg_vmstats),

				 GFP_KERNEL_ACCOUNT);
@@ -3664,9 +3647,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) 
	 * publish it here at the end of onlining. This matches the

	 * regular ID destruction during offlining.

	 */

	spin_lock(&memcg_idr_lock);

	idr_replace(&mem_cgroup_idr, memcg, memcg->id.id);

	spin_unlock(&memcg_idr_lock);

	xa_store(&mem_cgroup_ids, memcg->id.id, memcg, GFP_KERNEL);



	return 0;

offline_kmem: