+ mm-memcontrol-move-memcg_online_kmem-to-mem_cgroup_css_online.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: memcontrol: move memcg_online_kmem() to mem_cgroup_css_online()
has been added to the -mm tree.  Its filename is
     mm-memcontrol-move-memcg_online_kmem-to-mem_cgroup_css_online.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-move-memcg_online_kmem-to-mem_cgroup_css_online.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-move-memcg_online_kmem-to-mem_cgroup_css_online.patch

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------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
Subject: mm: memcontrol: move memcg_online_kmem() to mem_cgroup_css_online()

It will simplify the code if moving memcg_online_kmem() to
mem_cgroup_css_online() and do not need to set ->kmemcg_id to -1 to
indicate the memcg is offline.  In the next patch, ->kmemcg_id will be
used to sync list lru reparenting which requires not to change
->kmemcg_id.

Link: https://lkml.kernel.org/r/20220228122126.37293-10-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Alex Shi <alexs@kernel.org>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Fam Zheng <fam.zheng@bytedance.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kari Argillander <kari.argillander@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   37 ++++++++++++++++---------------------
 1 file changed, 16 insertions(+), 21 deletions(-)

--- a/mm/memcontrol.c~mm-memcontrol-move-memcg_online_kmem-to-mem_cgroup_css_online
+++ a/mm/memcontrol.c
@@ -3667,7 +3667,8 @@ static int memcg_online_kmem(struct mem_
 	if (cgroup_memory_nokmem)
 		return 0;
 
-	BUG_ON(memcg->kmemcg_id >= 0);
+	if (unlikely(mem_cgroup_is_root(memcg)))
+		return 0;
 
 	memcg_id = memcg_alloc_cache_id();
 	if (memcg_id < 0)
@@ -3693,7 +3694,10 @@ static void memcg_offline_kmem(struct me
 	struct mem_cgroup *parent;
 	int kmemcg_id;
 
-	if (memcg->kmemcg_id == -1)
+	if (cgroup_memory_nokmem)
+		return;
+
+	if (unlikely(mem_cgroup_is_root(memcg)))
 		return;
 
 	parent = parent_mem_cgroup(memcg);
@@ -3703,7 +3707,6 @@ static void memcg_offline_kmem(struct me
 	memcg_reparent_objcgs(memcg, parent);
 
 	kmemcg_id = memcg->kmemcg_id;
-	BUG_ON(kmemcg_id < 0);
 
 	/*
 	 * After we have finished memcg_reparent_objcgs(), all list_lrus
@@ -3714,7 +3717,6 @@ static void memcg_offline_kmem(struct me
 	memcg_drain_all_list_lrus(kmemcg_id, parent);
 
 	memcg_free_cache_id(kmemcg_id);
-	memcg->kmemcg_id = -1;
 }
 #else
 static int memcg_online_kmem(struct mem_cgroup *memcg)
@@ -5234,7 +5236,6 @@ mem_cgroup_css_alloc(struct cgroup_subsy
 {
 	struct mem_cgroup *parent = mem_cgroup_from_css(parent_css);
 	struct mem_cgroup *memcg, *old_memcg;
-	long error = -ENOMEM;
 
 	old_memcg = set_active_memcg(parent);
 	memcg = mem_cgroup_alloc();
@@ -5263,34 +5264,26 @@ mem_cgroup_css_alloc(struct cgroup_subsy
 		return &memcg->css;
 	}
 
-	/* The following stuff does not apply to the root */
-	error = memcg_online_kmem(memcg);
-	if (error)
-		goto fail;
-
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
 		static_branch_inc(&memcg_sockets_enabled_key);
 
 	return &memcg->css;
-fail:
-	mem_cgroup_id_remove(memcg);
-	mem_cgroup_free(memcg);
-	return ERR_PTR(error);
 }
 
 static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
+	if (memcg_online_kmem(memcg))
+		goto remove_id;
+
 	/*
 	 * A memcg must be visible for expand_shrinker_info()
 	 * by the time the maps are allocated. So, we allocate maps
 	 * here, when for_each_mem_cgroup() can't skip it.
 	 */
-	if (alloc_shrinker_info(memcg)) {
-		mem_cgroup_id_remove(memcg);
-		return -ENOMEM;
-	}
+	if (alloc_shrinker_info(memcg))
+		goto offline_kmem;
 
 	/* Online state pins memcg ID, memcg ID pins CSS */
 	refcount_set(&memcg->id.ref, 1);
@@ -5300,6 +5293,11 @@ static int mem_cgroup_css_online(struct
 		queue_delayed_work(system_unbound_wq, &stats_flush_dwork,
 				   2UL*HZ);
 	return 0;
+offline_kmem:
+	memcg_offline_kmem(memcg);
+remove_id:
+	mem_cgroup_id_remove(memcg);
+	return -ENOMEM;
 }
 
 static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
@@ -5357,9 +5355,6 @@ static void mem_cgroup_css_free(struct c
 	cancel_work_sync(&memcg->high_work);
 	mem_cgroup_remove_from_trees(memcg);
 	free_shrinker_info(memcg);
-
-	/* Need to offline kmem if online_css() fails */
-	memcg_offline_kmem(memcg);
 	mem_cgroup_free(memcg);
 }
 
_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-list_lru-transpose-the-array-of-per-node-per-memcg-lru-lists.patch
mm-introduce-kmem_cache_alloc_lru.patch
fs-introduce-alloc_inode_sb-to-allocate-filesystems-specific-inode.patch
fs-allocate-inode-by-using-alloc_inode_sb.patch
f2fs-allocate-inode-by-using-alloc_inode_sb.patch
nfs42-use-a-specific-kmem_cache-to-allocate-nfs4_xattr_entry.patch
mm-dcache-use-kmem_cache_alloc_lru-to-allocate-dentry.patch
xarray-use-kmem_cache_alloc_lru-to-allocate-xa_node.patch
mm-memcontrol-move-memcg_online_kmem-to-mem_cgroup_css_online.patch
mm-list_lru-allocate-list_lru_one-only-when-needed.patch
mm-list_lru-rename-memcg_drain_all_list_lrus-to-memcg_reparent_list_lrus.patch
mm-list_lru-replace-linear-array-with-xarray.patch
mm-memcontrol-reuse-memory-cgroup-id-for-kmem-id.patch
mm-memcontrol-fix-cannot-alloc-the-maximum-memcg-id.patch
mm-list_lru-rename-list_lru_per_memcg-to-list_lru_memcg.patch
mm-memcontrol-rename-memcg_cache_id-to-memcg_kmem_id.patch
mm-thp-fix-wrong-cache-flush-in-remove_migration_pmd.patch
mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch
mm-hugetlb-fix-missing-cache-flush-in-copy_huge_page_from_user.patch
mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte.patch
mm-shmem-fix-missing-cache-flush-in-shmem_mfill_atomic_pte.patch
mm-userfaultfd-fix-missing-cache-flush-in-mcopy_atomic_pte-and-__mcopy_atomic.patch
mm-replace-multiple-dcache-flush-with-flush_dcache_folio.patch
mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page.patch
mm-hugetlb-replace-hugetlb_free_vmemmap_enabled-with-a-static_key.patch
mm-sparsemem-use-page-table-lock-to-protect-kernel-pmd-operations.patch
selftests-vm-add-a-hugetlb-test-case.patch
mm-sparsemem-move-vmemmap-related-to-hugetlb-to-config_hugetlb_page_free_vmemmap.patch