From: Matthew Wilcox <willy@infradead.org>
Date: Tue, 12 Feb 2019 04:19:18 +0000 (-0500)
Subject: memcontrol: Convert mem_cgroup IDR to XArray
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=4354a5fb46733e5c6f4d61b7556165fcac5f5fbe;p=users%2Fwilly%2Fxarray.git

memcontrol: Convert mem_cgroup IDR to XArray

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index cdbb7a84cb6e..e80c8f0f1143 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4517,7 +4517,7 @@ static struct cftype mem_cgroup_legacy_files[] = {
 };
 
 /*
- * Private memory cgroup IDR
+ * Private memory cgroup XArray
  *
  * Swap-out records and page cache shadow entries need to store memcg
  * references in constrained space, so we maintain an ID space that is
@@ -4540,12 +4540,12 @@ static struct cftype mem_cgroup_legacy_files[] = {
  * those references are manageable from userspace.
  */
 
-static DEFINE_IDR(mem_cgroup_idr);
+static DEFINE_XARRAY_ALLOC1(mem_cgroups);
 
 static void mem_cgroup_id_remove(struct mem_cgroup *memcg)
 {
 	if (memcg->id.id > 0) {
-		idr_remove(&mem_cgroup_idr, memcg->id.id);
+		xa_erase(&mem_cgroups, memcg->id.id);
 		memcg->id.id = 0;
 	}
 }
@@ -4583,8 +4583,7 @@ 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_cgroups, id);
 }
 
 static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
@@ -4669,10 +4668,8 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 	if (!memcg)
 		return NULL;
 
-	memcg->id.id = idr_alloc(&mem_cgroup_idr, NULL,
-				 1, MEM_CGROUP_ID_MAX,
-				 GFP_KERNEL);
-	if (memcg->id.id < 0)
+	if (xa_alloc(&mem_cgroups, &memcg->id.id, NULL,
+			XA_LIMIT(0, MEM_CGROUP_ID_MAX - 1), GFP_KERNEL))
 		goto fail;
 
 	memcg->vmstats_local = alloc_percpu(struct memcg_vmstats_percpu);
@@ -4705,7 +4702,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 #ifdef CONFIG_CGROUP_WRITEBACK
 	INIT_LIST_HEAD(&memcg->cgwb_list);
 #endif
-	idr_replace(&mem_cgroup_idr, memcg, memcg->id.id);
+	xa_store(&mem_cgroups, memcg->id.id, memcg, GFP_KERNEL);
 	return memcg;
 fail:
 	mem_cgroup_id_remove(memcg);