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Patch "radix-tree: account nodes to memcg only if explicitly requested" has been added to the 4.6-stable tree

PATCH [email protected] 1 participant 1 message Aug 14, 2016

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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 4.6-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-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 05eb6e7263185a6bb0de9501ccf2addc52429414 Mon Sep 17 00:00:00 2001

From: Vladimir Davydov <[email protected]>
Date: Tue, 2 Aug 2016 14:03:01 -0700
Subject: radix-tree: account nodes to memcg only if explicitly requested

From: Vladimir Davydov <[email protected]>

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/[email protected] open here
Signed-off-by Vladimir Davydov <[email protected]>
Acked-by Johannes Weiner <[email protected]>
Acked-by Michal Hocko <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 fs/inode.c       |    2 +-
 lib/radix-tree.c |   14 ++++++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)
fs/inode.c +1 -1
@@ -344,7 +344,7 @@ 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);
lib/radix-tree.c +10 -4
@@ -228,10 +228,11 @@ 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;
 

@@ -254,8 +255,7 @@ 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_indirect_ptr(ret));
 	return ret;

@@ -302,6 +302,12 @@ 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 [email protected] are

queue-4.6/radix-tree-account-nodes-to-memcg-only-if-explicitly-requested.patch queue-4.6/mm-memcontrol-fix-memcg-id-ref-counter-on-swap-charge-move.patch queue-4.6/mm-memcontrol-fix-swap-counter-leak-on-swapout-from-offline-cgroup.patch