Patch "radix-tree: account nodes to memcg only if explicitly requested" has been added to the 4.7-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    radix-tree: account nodes to memcg only if explicitly requested

to the 4.7-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     radix-tree-account-nodes-to-memcg-only-if-explicitly-requested.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>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: radix-tree: account nodes to memcg only if explicitly requested

From: Vladimir Davydov <vdavydov@virtuozzo.com>

commit 05eb6e7263185a6bb0de9501ccf2addc52429414 upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/inode.c       |    2 +-
 lib/radix-tree.c |   14 ++++++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

--- 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);
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -274,10 +274,11 @@ radix_tree_node_alloc(struct radix_tree_
 
 		/*
 		 * 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;
 
@@ -300,8 +301,7 @@ radix_tree_node_alloc(struct radix_tree_
 		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;
@@ -348,6 +348,12 @@ static int __radix_tree_preload(gfp_t gf
 	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 < RADIX_TREE_PRELOAD_SIZE) {


Patches currently in stable-queue which might be from vdavydov@virtuozzo.com are

queue-4.7/radix-tree-account-nodes-to-memcg-only-if-explicitly-requested.patch
queue-4.7/mm-memcontrol-fix-memcg-id-ref-counter-on-swap-charge-move.patch
queue-4.7/mm-memcontrol-fix-swap-counter-leak-on-swapout-from-offline-cgroup.patch