From 05eb6e7263185a6bb0de9501ccf2addc52429414 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavydov@virtuozzo.com>
Date: Tue, 2 Aug 2016 14:03:01 -0700
Subject: [PATCH] radix-tree: account nodes to memcg only if explicitly
requested
Radix trees may be used not only for storing page cache pages, so
unconditionally accounting radix tree nodes to the current memory cgroup
is bad: if a radix tree node is used for storing data shared among
different cgroups we risk pinning dead memory cgroups forever.
So let's only account radix tree nodes if it was explicitly requested by
passing __GFP_ACCOUNT to INIT_RADIX_TREE. Currently, we only want to
account page cache entries, so mark mapping->page_tree so.
Fixes: 58e698af4c63 ("radix-tree: account radix_tree_node to memory cgroup")
Link: http://lkml.kernel.org/r/1470057188-7864-1-git-send-email-vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org> [4.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/inode.c | 2 +-
lib/radix-tree.c | 14 ++++++++++----
2 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/fs/inode.c b/fs/inode.c
index 9cef4e16aedab..ad445542c2858 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -345,7 +345,7 @@ EXPORT_SYMBOL(inc_nlink);
void address_space_init_once(struct address_space *mapping)
{
memset(mapping, 0, sizeof(*mapping));
- INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC);
+ INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC | __GFP_ACCOUNT);
spin_lock_init(&mapping->tree_lock);
init_rwsem(&mapping->i_mmap_rwsem);
INIT_LIST_HEAD(&mapping->private_list);
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 61b8fb529ceff..1b7bf73141418 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -277,10 +277,11 @@ radix_tree_node_alloc(struct radix_tree_root *root)
/*
* Even if the caller has preloaded, try to allocate from the
- * cache first for the new node to get accounted.
+ * cache first for the new node to get accounted to the memory
+ * cgroup.
*/
ret = kmem_cache_alloc(radix_tree_node_cachep,
- gfp_mask | __GFP_ACCOUNT | __GFP_NOWARN);
+ gfp_mask | __GFP_NOWARN);
if (ret)
goto out;
@@ -303,8 +304,7 @@ radix_tree_node_alloc(struct radix_tree_root *root)
kmemleak_update_trace(ret);
goto out;
}
- ret = kmem_cache_alloc(radix_tree_node_cachep,
- gfp_mask | __GFP_ACCOUNT);
+ ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
out:
BUG_ON(radix_tree_is_internal_node(ret));
return ret;
@@ -351,6 +351,12 @@ static int __radix_tree_preload(gfp_t gfp_mask, int nr)
struct radix_tree_node *node;
int ret = -ENOMEM;
+ /*
+ * Nodes preloaded by one cgroup can be be used by another cgroup, so
+ * they should never be accounted to any particular memory cgroup.
+ */
+ gfp_mask &= ~__GFP_ACCOUNT;
+
preempt_disable();
rtp = this_cpu_ptr(&radix_tree_preloads);
while (rtp->nr < nr) {